// Copyright (c) 2019-2024 Alexander Medvednikov. All rights reserved.
// Use of this source code is governed by an MIT license
// that can be found in the LICENSE file.
module c

import hash.fnv1a
import v.ast

const cgen_resolution_hash_prime = u64(1099511628211)
const cgen_resolution_hash_seed = u64(14695981039346656037)
const cgen_unwrap_generic_cache_salt = u64(0x9e3779b185ebca87)
const cgen_scope_var_type_cache_salt = u64(0xc2b2ae3d27d4eb4f)

// stable_type_symbol_hash returns a deterministic hash for generated helper names.
fn (mut g Gen) stable_type_symbol_hash(typ ast.Type) u64 {
    mut seen := map[string]bool{}
    return fnv1a.sum64_string(g.stable_type_symbol_key(typ, mut seen))
}

// stable_type_symbol_key builds a stable type descriptor without using table registration ids.
fn (mut g Gen) stable_type_symbol_key(typ ast.Type, mut seen map[string]bool) string {
    if typ == 0 {
        return '0'
    }
    mut resolved_typ := g.unwrap_generic(g.recheck_concrete_type(typ))
    if resolved_typ == 0 {
        resolved_typ = g.unwrap_generic(typ)
    }
    if resolved_typ == 0 {
        return '0'
    }
    sym := g.table.final_sym(resolved_typ)
    if sym.info is ast.Alias {
        parent_type := sym.info.parent_type.derive(resolved_typ)
        if parent_type.idx() != resolved_typ.idx() {
            return g.stable_type_symbol_key(parent_type, mut seen)
        }
    }
    flags := stable_type_symbol_flags(resolved_typ)
    base := '${sym.kind}:${stable_type_symbol_nominal_name(sym)}:${flags}'
    if seen[base] {
        return 'recursive:${base}'
    }
    seen[base] = true
    mut parts := [base]
    match sym.info {
        ast.Array {
            parts << 'array:${sym.info.nr_dims}:${g.stable_type_symbol_key(sym.info.elem_type, mut seen)}'
        }
        ast.ArrayFixed {
            parts << 'array_fixed:${sym.info.size}:${g.stable_type_symbol_key(sym.info.elem_type, mut seen)}'
        }
        ast.Chan {
            parts << 'chan:${sym.info.is_mut}:${g.stable_type_symbol_key(sym.info.elem_type, mut seen)}'
        }
        ast.Enum {
            parts << 'enum:${sym.info.vals.join(',')}:${g.stable_type_symbol_key(sym.info.typ, mut seen)}:${sym.info.is_flag}:${sym.info.is_multi_allowed}:${sym.info.is_typedef}'
        }
        ast.FnType {
            parts << 'fn:${sym.info.func.is_variadic}:${g.stable_type_symbol_key(sym.info.func.return_type, mut seen)}'
            for param in sym.info.func.params {
                parts << 'param:${param.is_mut}:${param.is_shared}:${param.is_atomic}:${g.stable_type_symbol_key(param.typ, mut seen)}'
            }
        }
        ast.GenericInst {
            parent_sym := g.table.sym(ast.new_type(sym.info.parent_idx))
            parts << 'generic_inst:${parent_sym.kind}:${stable_type_symbol_nominal_name(parent_sym)}'
            for concrete_type in sym.info.concrete_types {
                parts << g.stable_type_symbol_key(concrete_type, mut seen)
            }
        }
        ast.Interface {
            parts << 'interface:${sym.info.is_generic}'
            for embed in sym.info.embeds {
                parts << 'embed:${g.stable_type_symbol_key(embed, mut seen)}'
            }
            for field in sym.info.fields {
                parts << stable_type_symbol_field_key(mut g, field, mut seen)
            }
            for method in sym.info.methods {
                parts << stable_type_symbol_method_key(mut g, method, mut seen)
            }
        }
        ast.Map {
            parts << 'map:${g.stable_type_symbol_key(sym.info.key_type, mut seen)}:${g.stable_type_symbol_key(sym.info.value_type, mut seen)}'
        }
        ast.MultiReturn {
            for return_type in sym.info.types {
                parts << 'return:${g.stable_type_symbol_key(return_type, mut seen)}'
            }
        }
        ast.Struct {
            parts << 'struct:${sym.info.is_typedef}:${sym.info.is_union}:${sym.info.is_heap}:${sym.info.is_shared}:${sym.info.is_generic}'
            for embed in sym.info.embeds {
                parts << 'embed:${g.stable_type_symbol_key(embed, mut seen)}'
            }
            for field in sym.info.fields {
                parts << stable_type_symbol_field_key(mut g, field, mut seen)
            }
        }
        ast.SumType {
            parts << 'sum_type:${sym.info.is_anon}:${sym.info.is_generic}'
            for variant in sym.info.variants {
                parts << 'variant:${g.stable_type_symbol_key(variant, mut seen)}'
            }
            for field in sym.info.fields {
                parts << stable_type_symbol_field_key(mut g, field, mut seen)
            }
        }
        ast.Thread {
            parts << 'thread:${g.stable_type_symbol_key(sym.info.return_type, mut seen)}'
        }
        else {}
    }

    return parts.join('|')
}

// stable_type_symbol_nominal_name serializes source-level identity for named types.
fn stable_type_symbol_nominal_name(sym &ast.TypeSymbol) string {
    if sym.name.starts_with('_VAnonStruct') || sym.name.starts_with('_VAnonUnion') {
        return ''
    }
    return match sym.kind {
        .alias, .enum, .interface, .struct, .sum_type, .aggregate {
            '${sym.language}:${sym.mod}:${sym.name}'
        }
        else {
            ''
        }
    }
}

// stable_type_symbol_flags serializes the type flags that affect generated helper identity.
fn stable_type_symbol_flags(typ ast.Type) string {
    mut flags := []string{cap: 8}
    if typ.has_flag(.option) {
        flags << 'option'
    }
    if typ.has_flag(.result) {
        flags << 'result'
    }
    if typ.has_flag(.variadic) {
        flags << 'variadic'
    }
    if typ.has_flag(.generic) {
        flags << 'generic'
    }
    if typ.has_flag(.shared_f) {
        flags << 'shared'
    }
    if typ.has_flag(.atomic_f) {
        flags << 'atomic'
    }
    if typ.has_flag(.option_mut_param_t) {
        flags << 'option_mut_param'
    }
    flags << 'muls:${typ.nr_muls()}'
    return flags.join(',')
}

// stable_type_symbol_field_key adds field identity and type information to a type descriptor.
fn stable_type_symbol_field_key(mut g Gen, field ast.StructField, mut seen map[string]bool) string {
    return 'field:${field.name}:${field.is_embed}:${field.is_part_of_union}:${field.is_volatile}:${g.stable_type_symbol_key(field.typ, mut
        seen)}'
}

// stable_type_symbol_method_key adds method signature information to a type descriptor.
fn stable_type_symbol_method_key(mut g Gen, method ast.Fn, mut seen map[string]bool) string {
    mut parts := [
        'method:${method.name}:${method.is_variadic}:${g.stable_type_symbol_key(method.return_type, mut seen)}',
    ]
    for param in method.params {
        parts << 'param:${param.is_mut}:${param.is_shared}:${param.is_atomic}:${g.stable_type_symbol_key(param.typ, mut seen)}'
    }
    return parts.join(',')
}

@[inline]
fn cgen_resolution_hash_mix(key u64, value u64) u64 {
    return (key ^ value) * cgen_resolution_hash_prime
}

fn (mut g Gen) clear_type_resolution_caches() {
    g.unwrap_generic_cache.clear()
    g.resolved_scope_var_type_cache.clear()
}

fn (mut g Gen) current_sumtype_match_variant_type(ident ast.Ident, sumtype_type ast.Type) ast.Type {
    if g.cur_fn == unsafe { nil } || g.cur_concrete_types.len == 0 {
        return ast.Type(0)
    }
    mut branch_type := ast.Type(0)
    if typ := g.type_resolver.type_map[ident.name] {
        branch_type = typ
    }
    if branch_type == 0 {
        cname := c_name(ident.name)
        if cname != ident.name {
            if typ := g.type_resolver.type_map[cname] {
                branch_type = typ
            }
        }
    }
    if branch_type == 0 || branch_type == ast.void_type {
        return ast.Type(0)
    }
    variant_type := g.unwrap_generic(g.recheck_concrete_type(branch_type))
    if variant_type == 0 || variant_type == ast.void_type || variant_type.has_flag(.generic)
        || g.type_has_unresolved_generic_parts(variant_type) {
        return ast.Type(0)
    }
    mut parent_type := g.unwrap_generic(g.recheck_concrete_type(sumtype_type)).set_nr_muls(0)
    if parent_type != 0 && g.table.final_sym(parent_type).kind == .sum_type
        && g.table.sumtype_has_variant(parent_type, variant_type, false) {
        return variant_type
    }
    parent_type = g.resolve_current_fn_generic_param_type(ident.name).set_nr_muls(0)
    if parent_type == 0 || g.table.final_sym(parent_type).kind != .sum_type
        || !g.table.sumtype_has_variant(parent_type, variant_type, false) {
        return ast.Type(0)
    }
    return variant_type
}

fn (g &Gen) type_resolution_context_key() u64 {
    mut key := cgen_resolution_hash_seed
    if g.inside_struct_init {
        key = cgen_resolution_hash_mix(key, 1)
    }
    key = cgen_resolution_hash_mix(key, u64(g.cur_struct_init_typ))
    key = cgen_resolution_hash_mix(key, u64(g.cur_concrete_types.len))
    for concrete_type in g.cur_concrete_types {
        key = cgen_resolution_hash_mix(key, u64(concrete_type))
    }
    key = cgen_resolution_hash_mix(key, u64(g.active_call_concrete_types.len))
    for concrete_type in g.active_call_concrete_types {
        key = cgen_resolution_hash_mix(key, u64(concrete_type))
    }
    if g.comptime != unsafe { nil } {
        key = cgen_resolution_hash_mix(key, u64(g.comptime.comptime_loop_id))
        key = cgen_resolution_hash_mix(key, u64(g.comptime.comptime_for_field_type))
        key = cgen_resolution_hash_mix(key, u64(g.comptime.comptime_for_method_ret_type))
    }
    return key
}

@[inline]
fn (g &Gen) type_resolution_cache_key(typ ast.Type, salt u64) u64 {
    return cgen_resolution_hash_mix(g.type_resolution_context_key(), u64(typ)) ^ salt
}

@[inline]
fn (g &Gen) expr_resolution_cache_key(pos int, default_typ ast.Type, salt u64) u64 {
    if pos <= 0 {
        return 0
    }
    mut key := g.type_resolution_context_key()
    key = cgen_resolution_hash_mix(key, u64(g.fid + 2))
    key = cgen_resolution_hash_mix(key, u64(pos))
    key = cgen_resolution_hash_mix(key, u64(default_typ))
    return key ^ salt
}

@[inline]
fn (g &Gen) type_is_known_concrete(typ ast.Type) bool {
    if typ == 0 || typ.has_flag(.generic) {
        return false
    }
    idx := typ.idx()
    return idx <= ast.nil_type_idx
        || (idx < g.generic_parts_cache.len && g.generic_parts_cache[idx] == 1)
}

@[inline]
fn (mut g Gen) unwrap_generic(typ ast.Type) ast.Type {
    if typ == 0 {
        return typ
    }
    if !typ.has_flag(.generic) {
        idx := typ.idx()
        if idx <= ast.nil_type_idx
            || (idx < g.generic_parts_cache.len && g.generic_parts_cache[idx] == 1) {
            return typ
        }
    }
    return g.unwrap_generic_slow(typ)
}

fn (mut g Gen) unwrap_generic_slow(typ ast.Type) ast.Type {
    cache_key := g.type_resolution_cache_key(typ, cgen_unwrap_generic_cache_salt)
    if cached := g.unwrap_generic_cache[cache_key] {
        return cached
    }
    mut resolved_typ := g.recheck_concrete_type(typ)
    if resolved_typ == 0 {
        resolved_typ = typ
    }
    if !resolved_typ.has_flag(.generic) {
        resolved_idx := resolved_typ.idx()
        if resolved_idx <= ast.nil_type_idx
            || (resolved_idx < g.generic_parts_cache.len
            && g.generic_parts_cache[resolved_idx] == 1)
            || !g.type_has_unresolved_generic_parts(resolved_typ) {
            g.unwrap_generic_cache[cache_key] = resolved_typ
            return resolved_typ
        }
    }
    // NOTE: `convert_generic_type` should not mutate the table.
    //
    // It mutates if the generic type is for example `[]T` and the concrete
    // type is an array type that has not been registered yet.
    //
    // This should have already happened in the checker, since it also calls
    // `convert_generic_type`. `g.table` is made non-mut to make sure
    // no one else can accidentally mutates the table.
    current_generic_names := g.current_fn_generic_names()
    if current_generic_names.len > 0 && current_generic_names.len == g.cur_concrete_types.len {
        if t_typ := g.table.convert_generic_type(resolved_typ, current_generic_names,
            g.cur_concrete_types)
        {
            g.unwrap_generic_cache[cache_key] = t_typ
            return t_typ
        }
    } else if g.inside_struct_init {
        if g.cur_struct_init_typ != 0 {
            sym := g.table.sym(g.cur_struct_init_typ)
            if sym.info is ast.Struct {
                if sym.info.generic_types.len > 0 {
                    generic_names := sym.info.generic_types.map(g.table.sym(it).name)
                    mut concrete_types := sym.info.concrete_types.clone()
                    if concrete_types.len == 0 && sym.generic_types.len == generic_names.len
                        && sym.generic_types != sym.info.generic_types {
                        concrete_types = sym.generic_types.clone()
                    }
                    if t_typ := g.table.convert_generic_type(resolved_typ, generic_names,
                        concrete_types)
                    {
                        g.unwrap_generic_cache[cache_key] = t_typ
                        return t_typ
                    }
                }
            }
        }
    } else if resolved_typ != 0 && g.table.sym(resolved_typ).kind == .struct {
        // resolve selector `a.foo` where `a` is struct[T] on non generic function
        sym := g.table.sym(resolved_typ)
        if sym.info is ast.Struct {
            if sym.info.generic_types.len > 0 {
                generic_names := sym.info.generic_types.map(g.table.sym(it).name)
                mut concrete_types := sym.info.concrete_types.clone()
                if concrete_types.len == 0 && sym.generic_types.len == generic_names.len
                    && sym.generic_types != sym.info.generic_types {
                    concrete_types = sym.generic_types.clone()
                }
                if t_typ := g.table.convert_generic_type(resolved_typ, generic_names,
                    concrete_types)
                {
                    g.unwrap_generic_cache[cache_key] = t_typ
                    return t_typ
                }

                if t_typ := g.table.convert_generic_type(resolved_typ, generic_names,
                    g.cur_concrete_types)
                {
                    g.unwrap_generic_cache[cache_key] = t_typ
                    return t_typ
                }
            }
        }
    }
    if typ.has_flag(.generic) {
        if t_typ := g.type_resolver.resolve_bound_generic_type(typ) {
            g.unwrap_generic_cache[cache_key] = t_typ
            return t_typ
        }
    }
    g.unwrap_generic_cache[cache_key] = resolved_typ
    return resolved_typ
}

// Promotes literal element types in arrays (e.g. []int_literal -> []int, []float_literal -> []f64)
// so that array comparisons use the correct registered array type.
fn (mut g Gen) promote_literal_array_type(typ ast.Type) ast.Type {
    sym := g.table.sym(typ)
    if sym.info is ast.Array {
        promoted_elem := ast.mktyp(sym.info.elem_type)
        if promoted_elem != sym.info.elem_type {
            idx := g.table.find_or_register_array(promoted_elem)
            if idx > 0 {
                return ast.new_type(idx).derive(typ)
            }
        }
    }
    return typ
}

fn (mut g Gen) infer_branch_expr_type(stmts []ast.Stmt) ast.Type {
    if stmts.len == 0 {
        return ast.void_type
    }
    last_stmt := stmts.last()
    if last_stmt !is ast.ExprStmt {
        return ast.void_type
    }
    expr_stmt := last_stmt as ast.ExprStmt
    mut default_typ := expr_stmt.typ
    if default_typ == 0 || default_typ == ast.void_type {
        default_typ = expr_stmt.expr.type()
    }
    mut resolved_typ := g.resolved_expr_type(expr_stmt.expr, default_typ)
    if resolved_typ == 0 || resolved_typ == ast.void_type {
        resolved_typ = g.type_resolver.get_type_or_default(expr_stmt.expr, default_typ)
    }
    if resolved_typ == 0 || resolved_typ == ast.void_type {
        resolved_typ = default_typ
    }
    if resolved_typ == 0 || resolved_typ == ast.void_type {
        return ast.void_type
    }
    return g.unwrap_generic(g.recheck_concrete_type(resolved_typ))
}

fn (mut g Gen) expected_rhs_type_for_expr(pos int, node_type ast.Type) ast.Type {
    if pos < 0 || node_type == 0 || node_type == ast.void_type || !node_type.has_option_or_result() {
        return ast.void_type
    }
    expected_type := g.expected_rhs_type_by_pos[pos] or { return ast.void_type }
    if expected_type == 0 || expected_type == ast.void_type || expected_type.has_option_or_result() {
        return ast.void_type
    }
    resolved_expected_type := g.unwrap_generic(g.recheck_concrete_type(expected_type))
    if resolved_expected_type == 0 || resolved_expected_type == ast.void_type
        || resolved_expected_type.has_option_or_result() {
        return ast.void_type
    }
    return resolved_expected_type
}

fn (mut g Gen) infer_if_expr_type(node ast.IfExpr) ast.Type {
    if g.inside_return && g.inside_struct_init {
        for branch in node.branches {
            branch_typ := g.infer_branch_expr_type(branch.stmts)
            if branch_typ != 0 && branch_typ != ast.void_type {
                return branch_typ
            }
        }
    }
    if node.typ != 0 && node.typ != ast.void_type {
        expected_rhs_type := g.expected_rhs_type_for_expr(node.pos.pos, node.typ)
        if expected_rhs_type != ast.void_type {
            return expected_rhs_type
        }
        resolved := g.unwrap_generic(g.recheck_concrete_type(node.typ))
        // In generic functions, node.typ may have been mutated by the checker
        // to a concrete type from the last processed instantiation. When the
        // if-expr is used as a return expression, use the function's
        // return type instead, which correctly resolves via cur_concrete_types.
        // Only apply this override when the function's return type is actually
        // generic — otherwise the if-expression type is concrete and correct.
        if g.inside_return_expr && !g.inside_struct_init && g.cur_fn != unsafe { nil }
            && g.cur_concrete_types.len > 0 && g.cur_fn.return_type.has_flag(.generic) {
            fn_ret := g.unwrap_generic(g.recheck_concrete_type(g.cur_fn.return_type))
            if fn_ret != 0 && fn_ret != ast.void_type {
                if node.typ.has_flag(.result) && !fn_ret.has_flag(.result) {
                    return fn_ret.set_flag(.result)
                } else if node.typ.has_flag(.option) && !fn_ret.has_flag(.option) {
                    return fn_ret.set_flag(.option)
                }
                return fn_ret
            }
        }
        return resolved
    }
    for branch in node.branches {
        branch_typ := g.infer_branch_expr_type(branch.stmts)
        if branch_typ != 0 && branch_typ != ast.void_type {
            return branch_typ
        }
    }
    return ast.void_type
}

fn (mut g Gen) infer_match_expr_type(node ast.MatchExpr) ast.Type {
    if g.inside_return && g.inside_struct_init {
        for branch in node.branches {
            branch_typ := g.infer_branch_expr_type(branch.stmts)
            if branch_typ != 0 && branch_typ != ast.void_type {
                return branch_typ
            }
        }
    }
    if node.return_type != 0 && node.return_type != ast.void_type {
        expected_rhs_type := g.expected_rhs_type_for_expr(node.pos.pos, node.return_type)
        if expected_rhs_type != ast.void_type {
            return expected_rhs_type
        }
        resolved := g.unwrap_generic(g.recheck_concrete_type(node.return_type))
        // In generic functions, node.return_type may have been mutated by the checker
        // to a concrete type from the last processed instantiation. When the match is
        // used as a return expression, use the function's return type
        // instead, which correctly resolves via cur_concrete_types.
        // Only apply this override when the function's return type is actually
        // generic — otherwise the match expression type is concrete and correct.
        if g.inside_return_expr && !g.inside_struct_init && g.cur_fn != unsafe { nil }
            && g.cur_concrete_types.len > 0 && g.cur_fn.return_type.has_flag(.generic) {
            fn_ret := g.unwrap_generic(g.recheck_concrete_type(g.cur_fn.return_type))
            if fn_ret != 0 && fn_ret != ast.void_type {
                // Preserve option/result flags from the match's return_type
                if node.return_type.has_flag(.result) && !fn_ret.has_flag(.result) {
                    return fn_ret.set_flag(.result)
                } else if node.return_type.has_flag(.option) && !fn_ret.has_flag(.option) {
                    return fn_ret.set_flag(.option)
                }
                return fn_ret
            }
        }
        return resolved
    }
    for branch in node.branches {
        branch_typ := g.infer_branch_expr_type(branch.stmts)
        if branch_typ != 0 && branch_typ != ast.void_type {
            return branch_typ
        }
    }
    return ast.void_type
}

fn (mut g Gen) recheck_concrete_type(typ ast.Type) ast.Type {
    if typ == 0 {
        return typ
    }
    if g.cur_fn == unsafe { nil } || g.cur_concrete_types.len == 0 {
        return typ
    }
    idx := typ.idx()
    if idx <= ast.nil_type_idx || (!typ.has_flag(.generic) && idx < g.generic_parts_cache.len
        && g.generic_parts_cache[idx] == 1) {
        return typ
    }
    sym := g.table.sym(typ)
    match sym.info {
        ast.Struct, ast.Interface, ast.SumType {
            if sym.info.concrete_types.len > 0
                && !sym.info.concrete_types.any(it.has_flag(.generic)) {
                return typ
            }
        }
        ast.GenericInst {
            if sym.info.concrete_types.len > 0
                && !sym.info.concrete_types.any(it.has_flag(.generic)) {
                return typ
            }
        }
        else {}
    }

    if !typ.has_flag(.generic) && !g.type_has_unresolved_generic_parts(typ) {
        return typ
    }
    if g.cur_fn == unsafe { nil } || g.cur_concrete_types.len == 0 {
        return typ
    }
    generic_names := g.current_fn_generic_names()
    if generic_names.len == 0 || generic_names.len != g.cur_concrete_types.len {
        return typ
    }
    concrete_types := g.cur_concrete_types
    if resolved_typ := g.table.convert_generic_type(typ, generic_names, concrete_types) {
        return resolved_typ
    }
    mut muttable := unsafe { &ast.Table(g.table) }
    unwrapped_typ := muttable.unwrap_generic_type_ex(typ, generic_names, concrete_types, true)
    if unwrapped_typ != typ {
        return unwrapped_typ
    }
    return typ
}

@[inline]
fn (g &Gen) has_current_generic_context() bool {
    return g.cur_fn != unsafe { nil } && g.cur_concrete_types.len > 0
}

@[inline]
fn (mut g Gen) type_needs_generic_resolution(typ ast.Type) bool {
    if typ == 0 {
        return false
    }
    if typ.has_flag(.generic) {
        return true
    }
    if typ.idx() <= ast.nil_type_idx {
        return false
    }
    if (g.cur_fn == unsafe { nil } || g.cur_concrete_types.len == 0)
        && !g.has_active_call_generic_context() {
        return false
    }
    idx := typ.idx()
    if idx <= ast.nil_type_idx
        || (idx < g.generic_parts_cache.len && g.generic_parts_cache[idx] == 1) {
        return false
    }
    return g.type_has_unresolved_generic_parts(typ)
}

// is_expr_smartcast_to_sumtype checks if expr is a smartcast variable/field
// whose original type is the given sumtype. This is used to prevent sumtype
// variant unwrapping when passing a smartcast expression to a function
// that expects the original sumtype.
fn (mut g Gen) is_expr_smartcast_to_sumtype(expr ast.Expr, expected_sumtype ast.Type) bool {
    scope := g.file.scope.innermost(expr.pos().pos)
    if expr is ast.SelectorExpr {
        v := scope.find_struct_field(expr.expr.str(), expr.expr_type, expr.field_name)
        if v != unsafe { nil } && v.smartcasts.len > 0 {
            orig_type := g.unwrap_generic(g.recheck_concrete_type(v.orig_type))
            resolved_expected_sumtype := g.unwrap_generic(g.recheck_concrete_type(expected_sumtype))
            return orig_type == resolved_expected_sumtype
        }
    } else if expr is ast.Ident {
        if v := scope.find_var(expr.name) {
            if v.smartcasts.len > 0 && v.orig_type == expected_sumtype {
                return true
            }
        }
    }
    return false
}

// expr_has_or_block checks if an expression has an `or {}` block that
// unwraps an option/result type.
fn (g Gen) expr_has_or_block(expr ast.Expr) bool {
    return match expr {
        ast.CallExpr { expr.or_block.kind != .absent }
        ast.Ident { expr.or_expr.kind != .absent }
        ast.IndexExpr { expr.or_expr.kind != .absent }
        ast.SelectorExpr { expr.or_block.kind != .absent }
        ast.PrefixExpr { expr.or_block.kind != .absent }
        ast.InfixExpr { expr.or_block.kind != .absent }
        ast.ComptimeCall { expr.or_block.kind != .absent }
        ast.ComptimeSelector { expr.or_block.kind != .absent }
        else { false }
    }
}

fn (g &Gen) is_auto_deref_source_ident(expr ast.Expr) bool {
    if expr is ast.Ident {
        ident := expr as ast.Ident
        if ident.obj is ast.Var && ident.obj.is_auto_deref {
            return true
        }
        if source_var := ident.scope.find_var(ident.name) {
            return source_var.is_auto_deref
        }
    }
    return false
}

fn (g &Gen) auto_deref_source_type_is_pointer(expr ast.Expr) bool {
    if expr !is ast.Ident || g.cur_fn == unsafe { nil } || !expr.is_auto_deref_var() {
        return false
    }
    ident := expr as ast.Ident
    for param in g.cur_fn.params {
        if param.name == ident.name {
            source_typ := if param.orig_typ != 0 { param.orig_typ } else { param.typ }
            return source_typ.is_any_kind_of_pointer()
        }
    }
    return false
}

fn (mut g Gen) resolved_scope_var_type(expr ast.Ident) ast.Type {
    if g.has_active_call_generic_context() {
        return g.resolved_scope_var_type_uncached(expr)
    }
    cache_key := g.expr_resolution_cache_key(expr.pos.pos, 0, cgen_scope_var_type_cache_salt)
    if cache_key != 0 {
        if cached := g.resolved_scope_var_type_cache[cache_key] {
            return cached
        }
    }
    resolved := g.resolved_scope_var_type_uncached(expr)
    if cache_key != 0 && resolved != 0 {
        g.resolved_scope_var_type_cache[cache_key] = resolved
    }
    return resolved
}

// type_alias_chain_idxs returns the idxs of `typ` and of every type it aliases,
// transitively, down to the first non-alias type. Comparison is by idx only,
// so flags and pointer levels are ignored.
fn (g &Gen) type_alias_chain_idxs(typ ast.Type) []int {
    mut idxs := [typ.idx()]
    mut cur := typ
    for {
        sym := g.table.sym(cur)
        if sym.info is ast.Alias {
            parent := sym.info.parent_type
            pidx := parent.idx()
            if pidx in idxs {
                break
            }
            idxs << pidx
            cur = parent
        } else {
            break
        }
    }
    return idxs
}

// alias_chain_equivalent reports whether `a` and `b` denote the same type modulo
// alias naming: one type's alias chain (the type itself plus the types it
// aliases, transitively) contains the other. This is stricter than comparing
// fully unaliased base types, so distinct aliases that merely share an
// underlying representation (e.g. `type String = u8` and `type Void = u8`) are
// NOT treated as equivalent, while genuine alias/original pairs (e.g. a variant
// `Bar` together with `type Foo = Bar`) still match by runtime tag.
fn (g &Gen) alias_chain_equivalent(a ast.Type, b ast.Type) bool {
    if a.nr_muls() != b.nr_muls() || a.has_flag(.option) != b.has_flag(.option) {
        return false
    }
    if a.idx() == b.idx() {
        return true
    }
    return b.idx() in g.type_alias_chain_idxs(a) || a.idx() in g.type_alias_chain_idxs(b)
}

fn (mut g Gen) type_idx_exprs_for_types(types []ast.Type) []string {
    mut matches := []string{}
    mut seen := map[string]bool{}
    for typ in types {
        index_expr := g.type_sidx(typ)
        if index_expr !in seen {
            seen[index_expr] = true
            matches << index_expr
        }
    }
    return matches
}

fn (mut g Gen) matching_sumtype_variant_types(parent_type ast.Type, target_type ast.Type) []ast.Type {
    variants := g.sumtype_runtime_variants(parent_type)
    target := g.unwrap_generic(target_type)
    mut matches := []ast.Type{}
    mut seen := map[string]bool{}
    for variant in variants {
        if g.alias_chain_equivalent(g.unwrap_generic(variant), target) {
            index_expr := g.type_sidx(variant)
            if index_expr !in seen {
                seen[index_expr] = true
                matches << variant
            }
        }
    }
    if matches.len > 0 {
        return matches
    }
    for variant in variants {
        if g.is_exact_sumtype_variant_match(variant, target_type) {
            return [variant]
        }
    }
    return [target_type]
}

fn (mut g Gen) matching_sumtype_variant_type_idx_exprs(parent_type ast.Type, target_type ast.Type) []string {
    return g.type_idx_exprs_for_types(g.matching_sumtype_variant_types(parent_type, target_type))
}

fn (mut g Gen) matching_interface_variant_types(interface_sym ast.TypeSymbol, target_type ast.Type) []ast.Type {
    if interface_sym.info !is ast.Interface {
        return []
    }
    target := g.unwrap_generic(target_type)
    info := interface_sym.info as ast.Interface
    mut matches := []ast.Type{}
    mut seen := map[string]bool{}
    for variant in g.runtime_interface_variants(info) {
        variant_sym := g.table.sym(variant)
        if variant_sym.kind in [.interface, .aggregate] {
            continue
        }
        if variant_sym.info is ast.Struct && variant_sym.info.is_unresolved_generic() {
            continue
        }
        if !g.alias_chain_equivalent(g.unwrap_generic(variant), target) {
            continue
        }
        index_expr := g.type_sidx(variant)
        if index_expr !in seen {
            seen[index_expr] = true
            matches << variant
        }
    }
    if matches.len > 0 {
        return matches
    }
    return [target_type]
}

fn (mut g Gen) matching_interface_variant_index_exprs(interface_sym ast.TypeSymbol, target_type ast.Type) []string {
    if interface_sym.info !is ast.Interface {
        return []
    }
    matching_variants := g.matching_interface_variant_types(interface_sym, target_type)
    mut matches := []string{}
    mut seen := map[string]bool{}
    for variant in matching_variants {
        cctype := g.cc_type(ast.mktyp(variant), true)
        index_expr := '_${interface_sym.cname}_${cctype}_index'
        if index_expr !in seen {
            seen[index_expr] = true
            matches << index_expr
        }
    }
    if matches.len > 0 {
        return matches
    }
    cctype := g.cc_type(ast.mktyp(target_type), true)
    return ['_${interface_sym.cname}_${cctype}_index']
}

fn (mut g Gen) matching_interface_variant_type_idx_exprs(interface_sym ast.TypeSymbol, target_type ast.Type) []string {
    if interface_sym.info !is ast.Interface {
        return []
    }
    return g.type_idx_exprs_for_types(g.matching_interface_variant_types(interface_sym, target_type))
}

fn (mut g Gen) write_type_tag_condition(tag_expr string, cmp_op string, index_exprs []string) {
    if index_exprs.len == 0 {
        g.write(if cmp_op == '==' { 'false' } else { 'true' })
        return
    }
    if index_exprs.len > 1 {
        g.write('(')
    }
    joiner := if cmp_op == '==' { ' || ' } else { ' && ' }
    for i, index_expr in index_exprs {
        if i > 0 {
            g.write(joiner)
        }
        g.write('${tag_expr} ${cmp_op} ${index_expr}')
    }
    if index_exprs.len > 1 {
        g.write(')')
    }
}

fn (mut g Gen) resolved_scope_var_type_uncached(expr ast.Ident) ast.Type {
    mut scope := if expr.scope != unsafe { nil } {
        expr.scope.innermost(expr.pos.pos)
    } else {
        expr.scope
    }
    if scope == unsafe { nil } || scope.find_var(expr.name) == none {
        scope = if g.file.scope != unsafe { nil } {
            g.file.scope.innermost(expr.pos.pos)
        } else {
            expr.scope
        }
    }
    if scope == unsafe { nil } {
        return 0
    }
    if mut v := scope.find_var(expr.name) {
        mut refreshed_expr_type := ast.Type(0)
        if v.generic_typ != 0 {
            refreshed_generic_type := g.unwrap_generic(g.recheck_concrete_type(v.generic_typ))
            if refreshed_generic_type != 0 {
                v.typ = refreshed_generic_type
                v.orig_type = ast.no_type
                v.smartcasts = []
                v.is_unwrapped = false
            }
        }
        if !v.is_arg && v.expr !is ast.EmptyExpr && v.pos.pos > 0 && v.pos.pos < expr.pos.pos
            && !(v.expr is ast.Ident && v.expr.name == expr.name)
            && ((g.cur_fn != unsafe { nil } && g.cur_concrete_types.len > 0)
            || v.typ.has_flag(.generic)
            || g.type_has_unresolved_generic_parts(v.typ)) {
            resolved_expr_type := g.resolved_expr_type(v.expr, v.typ)
            if resolved_expr_type != 0 {
                refreshed_expr_type = g.unwrap_generic(g.recheck_concrete_type(resolved_expr_type))
                if g.type_has_unresolved_generic_parts(refreshed_expr_type) {
                    call_like_type := g.resolved_call_like_expr_type(v.expr)
                    if call_like_type != 0 && !call_like_type.has_flag(.generic)
                        && !g.type_has_unresolved_generic_parts(call_like_type) {
                        refreshed_expr_type = call_like_type
                    }
                }
                // Keep `mut x := param` as a value copy when re-resolving locals,
                // unless the original mut parameter type was already a pointer.
                if g.is_auto_deref_source_ident(v.expr) && refreshed_expr_type.is_ptr()
                    && !g.auto_deref_source_type_is_pointer(v.expr) {
                    refreshed_expr_type = refreshed_expr_type.deref()
                }
                // If the variable was initialized with an `or {}` block that
                // unwraps the option/result, clear the flag from the resolved type
                if refreshed_expr_type.has_option_or_result() && g.expr_has_or_block(v.expr) {
                    refreshed_expr_type = refreshed_expr_type.clear_option_and_result()
                }
                $if trace_ci_fixes ? {
                    if g.file.path.contains('comptime_for_in_options_struct_test.v')
                        && expr.name in ['v', 'w'] {
                        current_name := if v.typ == 0 { '0' } else { g.table.type_to_str(v.typ) }
                        resolved_name := if refreshed_expr_type == 0 {
                            '0'
                        } else {
                            g.table.type_to_str(refreshed_expr_type)
                        }
                        orig_name := if v.orig_type == 0 {
                            '0'
                        } else {
                            g.table.type_to_str(v.orig_type)
                        }
                        eprintln('resolved_scope_var_type refresh ${expr.name}: current=${current_name} expr=${typeof(v.expr).name} resolved=${resolved_name} unwrapped=${v.is_unwrapped} orig=${orig_name}')
                    }
                }
                if v.is_unwrapped && refreshed_expr_type.has_option_or_result() {
                    v.orig_type = refreshed_expr_type
                    v.typ = refreshed_expr_type.clear_option_and_result()
                } else {
                    v.typ = refreshed_expr_type
                    if !v.is_unwrapped && v.smartcasts.len == 0 {
                        v.orig_type = ast.no_type
                    }
                }
            }
        }
        if (v.is_unwrapped || v.smartcasts.len > 0) && scope.parent != unsafe { nil } {
            if mut parent_v := scope.parent.find_var(expr.name) {
                if parent_v.generic_typ != 0 {
                    refreshed_parent_type :=
                        g.unwrap_generic(g.recheck_concrete_type(parent_v.generic_typ))
                    if refreshed_parent_type != 0 {
                        parent_v.typ = refreshed_parent_type
                    }
                }
                if !parent_v.is_arg && parent_v.expr !is ast.EmptyExpr && parent_v.pos.pos > 0
                    && parent_v.pos.pos < expr.pos.pos && !(parent_v.expr is ast.Ident
                    && parent_v.expr.name == expr.name)
                    && ((g.cur_fn != unsafe { nil } && g.cur_concrete_types.len > 0)
                    || parent_v.typ.has_flag(.generic)
                    || g.type_has_unresolved_generic_parts(parent_v.typ)) {
                    resolved_parent_expr_type := g.resolved_expr_type(parent_v.expr, parent_v.typ)
                    if resolved_parent_expr_type != 0 {
                        mut refreshed_parent_type :=
                            g.unwrap_generic(g.recheck_concrete_type(resolved_parent_expr_type))
                        if g.type_has_unresolved_generic_parts(parent_v.typ) {
                            call_like_type := g.resolved_call_like_expr_type(parent_v.expr)
                            if call_like_type != 0 && !call_like_type.has_flag(.generic)
                                && !g.type_has_unresolved_generic_parts(call_like_type) {
                                parent_v.typ = call_like_type
                            }
                        }
                        if g.is_auto_deref_source_ident(parent_v.expr)
                            && refreshed_parent_type.is_ptr()
                            && !g.auto_deref_source_type_is_pointer(parent_v.expr) {
                            refreshed_parent_type = refreshed_parent_type.deref()
                        }
                        parent_v.typ = refreshed_parent_type
                    }
                }
                if v.is_unwrapped {
                    parent_orig_type := if parent_v.orig_type != ast.no_type
                        && parent_v.orig_type.has_option_or_result() {
                        parent_v.orig_type
                    } else {
                        parent_v.typ
                    }
                    if parent_orig_type.has_option_or_result() {
                        v.orig_type = parent_orig_type
                        v.typ = parent_orig_type.clear_option_and_result()
                    }
                } else if v.smartcasts.len > 0 && parent_v.typ != 0 && v.orig_type == ast.no_type {
                    v.orig_type = if parent_v.orig_type != ast.no_type {
                        parent_v.orig_type
                    } else {
                        parent_v.typ
                    }
                }
            }
        }
        if v.is_inherited && scope.parent != unsafe { nil } {
            if mut parent_v := scope.parent.find_var(expr.name) {
                by_value_auto_deref_capture := !v.is_auto_deref && parent_v.is_auto_deref
                    && parent_v.typ.is_ptr()
                if by_value_auto_deref_capture {
                    if parent_v.generic_typ != 0 {
                        refreshed_parent_type :=
                            g.unwrap_generic(g.recheck_concrete_type(parent_v.generic_typ))
                        if refreshed_parent_type != 0 {
                            parent_v.typ = refreshed_parent_type
                        }
                    }
                    if parent_v.expr !is ast.EmptyExpr
                        && ((g.cur_fn != unsafe { nil } && g.cur_concrete_types.len > 0)
                        || parent_v.typ.has_flag(.generic)
                        || g.type_has_unresolved_generic_parts(parent_v.typ)) {
                        resolved_parent_type := g.resolved_expr_type(parent_v.expr, parent_v.typ)
                        if resolved_parent_type != 0 {
                            parent_v.typ =
                                g.unwrap_generic(g.recheck_concrete_type(resolved_parent_type))
                        }
                    }
                    if parent_v.typ != 0 {
                        resolved_parent_type :=
                            g.unwrap_generic(g.recheck_concrete_type(parent_v.typ))
                        if resolved_parent_type != 0 {
                            return if resolved_parent_type.is_ptr() {
                                resolved_parent_type.deref()
                            } else {
                                resolved_parent_type
                            }
                        }
                    }
                } else {
                    if parent_v.generic_typ != 0 {
                        refreshed_parent_type :=
                            g.unwrap_generic(g.recheck_concrete_type(parent_v.generic_typ))
                        if refreshed_parent_type != 0 {
                            parent_v.typ = refreshed_parent_type
                        }
                    }
                    if parent_v.smartcasts.len > 0 {
                        smartcast_type := if parent_v.ct_type_var == .smartcast {
                            g.type_resolver.get_type(expr)
                        } else {
                            g.exposed_smartcast_type(parent_v.orig_type,
                                parent_v.smartcasts.last(), parent_v.is_mut)
                        }
                        return g.unwrap_generic(g.recheck_concrete_type(smartcast_type))
                    }
                    if parent_v.expr !is ast.EmptyExpr
                        && ((g.cur_fn != unsafe { nil } && g.cur_concrete_types.len > 0)
                        || parent_v.typ.has_flag(.generic)
                        || g.type_has_unresolved_generic_parts(parent_v.typ)) {
                        resolved_parent_type := g.resolved_expr_type(parent_v.expr, parent_v.typ)
                        if resolved_parent_type != 0 {
                            resolved_parent :=
                                g.unwrap_generic(g.recheck_concrete_type(resolved_parent_type))
                            if g.type_has_unresolved_generic_parts(resolved_parent) {
                                call_like_type := g.resolved_call_like_expr_type(parent_v.expr)
                                if call_like_type != 0 && !call_like_type.has_flag(.generic)
                                    && !g.type_has_unresolved_generic_parts(call_like_type) {
                                    return call_like_type
                                }
                            }
                            return resolved_parent
                        }
                    }
                    if parent_v.typ != 0 {
                        return g.unwrap_generic(g.recheck_concrete_type(parent_v.typ))
                    }
                }
            }
        }
        if v.smartcasts.len > 0 {
            smartcast_type := if v.ct_type_var == .smartcast {
                g.type_resolver.get_type(expr)
            } else {
                g.exposed_smartcast_type(v.orig_type, v.smartcasts.last(), v.is_mut)
            }
            return g.unwrap_generic(g.recheck_concrete_type(smartcast_type))
        }
        if v.is_unwrapped {
            $if trace_ci_fixes ? {
                if g.file.path.contains('comptime_for_in_options_struct_test.v')
                    && expr.name in ['v', 'w'] {
                    typ_name := if v.typ == 0 { '0' } else { g.table.type_to_str(v.typ) }
                    orig_name := if v.orig_type == 0 {
                        '0'
                    } else {
                        g.table.type_to_str(v.orig_type)
                    }
                    refreshed_name := if refreshed_expr_type == 0 {
                        '0'
                    } else {
                        g.table.type_to_str(refreshed_expr_type)
                    }
                    eprintln('resolved_scope_var_type unwrapped ${expr.name}: typ=${typ_name} orig=${orig_name} refreshed=${refreshed_name}')
                }
            }
            if refreshed_expr_type != 0 && refreshed_expr_type.has_option_or_result() {
                return g.unwrap_generic(g.recheck_concrete_type(refreshed_expr_type.clear_option_and_result()))
            }
            unwrapped_type := if v.orig_type != ast.no_type && v.orig_type.has_option_or_result() {
                v.orig_type.clear_option_and_result()
            } else {
                v.typ.clear_option_and_result()
            }
            if unwrapped_type != 0 && unwrapped_type != ast.void_type {
                return g.unwrap_generic(g.recheck_concrete_type(unwrapped_type))
            }
        }
        if v.typ != 0 {
            return g.unwrap_generic(g.recheck_concrete_type(v.typ))
        }
    }
    return 0
}

fn (mut g Gen) resolved_ident_is_auto_heap_not_stack(expr ast.Ident) bool {
    if expr.obj is ast.Var {
        if expr.obj.is_auto_heap && !expr.obj.is_stack_obj {
            return true
        }
    }
    if expr.scope != unsafe { nil } {
        if v := expr.scope.find_var(expr.name) {
            return v.is_auto_heap && !v.is_stack_obj
        }
    }
    return false
}

fn (mut g Gen) resolved_ident_is_auto_heap(expr ast.Ident) bool {
    if expr.obj is ast.Var && expr.obj.is_auto_heap {
        return true
    }
    if expr.scope != unsafe { nil } {
        if v := expr.scope.find_var(expr.name) {
            return v.is_auto_heap
        }
    }
    return false
}

fn (g &Gen) resolved_ident_is_auto_deref(expr ast.Ident) bool {
    if expr.scope != unsafe { nil } {
        if v := expr.scope.find_var(expr.name) {
            return v.is_auto_deref
        }
    }
    if expr.obj is ast.Var {
        return expr.obj.is_auto_deref
    }
    return false
}

fn (g &Gen) resolved_ident_is_by_value_auto_deref_capture(expr ast.Ident) bool {
    if expr.scope == unsafe { nil } || expr.scope.parent == unsafe { nil } {
        return false
    }
    scope_var := expr.scope.find_var(expr.name) or { return false }
    if !scope_var.is_inherited || scope_var.is_auto_deref {
        return false
    }
    parent_var := expr.scope.parent.find_var(expr.name) or { return false }
    return parent_var.is_auto_deref && parent_var.typ.is_ptr()
}

fn (g &Gen) expr_is_auto_deref_var(expr ast.Expr) bool {
    return match expr {
        ast.Ident { g.resolved_ident_is_auto_deref(expr) }
        else { expr.is_auto_deref_var() }
    }
}

// scope_ident_is_auto_heap reports whether `expr`'s scope variable has
// is_auto_heap set. Unlike `resolved_ident_is_auto_heap`, this ignores
// `expr.obj.is_auto_heap` because a use-site Ident's obj copy may have been
// toggled by `mark_as_referenced` even when the declaration was emitted as
// a value (e.g. vars declared inside nested scopes where fn_scope.find_var
// misses them).
fn (mut g Gen) scope_ident_is_auto_heap(expr ast.Ident) bool {
    if expr.scope != unsafe { nil } {
        if v := expr.scope.find_var(expr.name) {
            return v.is_auto_heap
        }
    }
    return false
}

fn (mut g Gen) resolved_ident_array_elem_type(expr ast.Ident) ast.Type {
    scope_type := g.resolved_scope_var_type(expr)
    if scope_type != 0 {
        elem_type := g.recheck_concrete_type(g.table.value_type(g.unwrap_generic(scope_type)))
        if elem_type != 0 {
            return g.unwrap_generic(elem_type)
        }
    }
    if expr.obj !is ast.Var {
        return 0
    }
    var_obj := expr.obj as ast.Var
    if var_obj.expr is ast.ArrayInit {
        array_init := var_obj.expr as ast.ArrayInit
        if array_init.elem_type != 0 {
            return g.unwrap_generic(g.recheck_concrete_type(array_init.elem_type))
        }
        if array_init.typ != 0 {
            elem_type :=
                g.recheck_concrete_type(g.table.value_type(g.unwrap_generic(array_init.typ)))
            if elem_type != 0 {
                return g.unwrap_generic(elem_type)
            }
        }
    }
    if var_obj.typ != 0 {
        elem_type := g.recheck_concrete_type(g.table.value_type(g.unwrap_generic(var_obj.typ)))
        if elem_type != 0 {
            return g.unwrap_generic(elem_type)
        }
    }
    return 0
}

fn (mut g Gen) resolved_ident_map_key_type(expr ast.Ident) ast.Type {
    scope_type := g.resolved_scope_var_type(expr)
    if scope_type != 0 {
        typ_sym := g.table.final_sym(g.unwrap_generic(scope_type))
        if typ_sym.kind == .map {
            key_type := g.recheck_concrete_type(typ_sym.map_info().key_type)
            if key_type != 0 {
                return g.unwrap_generic(key_type)
            }
        }
    }
    if expr.obj !is ast.Var {
        return 0
    }
    var_obj := expr.obj as ast.Var
    if var_obj.expr is ast.MapInit {
        map_init := var_obj.expr as ast.MapInit
        if map_init.key_type != 0 {
            return g.unwrap_generic(g.recheck_concrete_type(map_init.key_type))
        }
    }
    if var_obj.typ != 0 {
        typ_sym := g.table.final_sym(g.unwrap_generic(var_obj.typ))
        if typ_sym.kind == .map {
            key_type := g.recheck_concrete_type(typ_sym.map_info().key_type)
            if key_type != 0 {
                return g.unwrap_generic(key_type)
            }
        }
    }
    return 0
}

fn (mut g Gen) resolved_ident_map_value_type(expr ast.Ident) ast.Type {
    scope_type := g.resolved_scope_var_type(expr)
    if scope_type != 0 {
        typ_sym := g.table.final_sym(g.unwrap_generic(scope_type))
        if typ_sym.kind == .map {
            val_type := g.recheck_concrete_type(typ_sym.map_info().value_type)
            if val_type != 0 {
                return g.unwrap_generic(val_type)
            }
        }
    }
    if expr.obj !is ast.Var {
        return 0
    }
    var_obj := expr.obj as ast.Var
    if var_obj.expr is ast.MapInit {
        map_init := var_obj.expr as ast.MapInit
        if map_init.value_type != 0 {
            return g.unwrap_generic(g.recheck_concrete_type(map_init.value_type))
        }
    }
    if var_obj.typ != 0 {
        typ_sym := g.table.final_sym(g.unwrap_generic(var_obj.typ))
        if typ_sym.kind == .map {
            val_type := g.recheck_concrete_type(typ_sym.map_info().value_type)
            if val_type != 0 {
                return g.unwrap_generic(val_type)
            }
        }
    }
    return 0
}

fn (mut g Gen) resolved_map_key_value_types(map_type ast.Type, fallback_key_type ast.Type, fallback_value_type ast.Type) (ast.Type, ast.Type) {
    mut key_type := g.unwrap_generic(g.recheck_concrete_type(fallback_key_type))
    mut value_type := g.unwrap_generic(g.recheck_concrete_type(fallback_value_type))
    resolved_map_type := g.unwrap_generic(g.recheck_concrete_type(map_type))
    map_sym := g.table.final_sym(resolved_map_type)
    if map_sym.kind == .map {
        map_info := map_sym.map_info()
        resolved_key := g.unwrap_generic(g.recheck_concrete_type(map_info.key_type))
        resolved_value := g.unwrap_generic(g.recheck_concrete_type(map_info.value_type))
        if resolved_key != 0 {
            key_type = resolved_key
        }
        if resolved_value != 0 {
            value_type = resolved_value
        }
        if key_type == ast.usize_type || value_type == ast.usize_type {
            name_key_type, name_value_type := g.resolved_map_types_from_name(map_sym.name)
            if key_type == ast.usize_type && name_key_type != 0 {
                key_type = name_key_type
            }
            if value_type == ast.usize_type && name_value_type != 0 {
                value_type = name_value_type
            }
        }
    }
    if key_type == 0 {
        key_type = fallback_key_type
    }
    if value_type == 0 {
        value_type = fallback_value_type
    }
    return key_type, value_type
}

fn (mut g Gen) resolved_map_type_from_expr(expr ast.Expr, default_type ast.Type) ast.Type {
    mut map_type := g.recheck_concrete_type(default_type)
    resolved_type := g.recheck_concrete_type(g.resolved_expr_type(expr, default_type))
    if resolved_type != 0
        && (g.cur_concrete_types.len > 0 || map_type == 0 || map_type.has_flag(.generic)
        || g.type_has_unresolved_generic_parts(map_type)
        || g.unwrap_generic(resolved_type) != g.unwrap_generic(map_type)) {
        map_type = resolved_type
    }
    return map_type
}

fn (mut g Gen) resolved_array_elem_type_from_name(name string) ast.Type {
    if !name.starts_with('[]') {
        return 0
    }
    elem_type := g.table.find_type(name[2..])
    if elem_type != 0 {
        return g.unwrap_generic(g.recheck_concrete_type(elem_type))
    }
    return 0
}

fn split_map_type_name(name string) (string, string) {
    if !name.starts_with('map[') {
        return '', ''
    }
    mut depth := 1
    mut i := 4
    for i < name.len {
        ch := name[i]
        if ch == `[` {
            depth++
        } else if ch == `]` {
            depth--
            if depth == 0 {
                break
            }
        }
        i++
    }
    if depth != 0 || i >= name.len {
        return '', ''
    }
    return name[4..i], name[i + 1..]
}

fn (mut g Gen) resolved_map_types_from_name(name string) (ast.Type, ast.Type) {
    key_name, val_name := split_map_type_name(name)
    if key_name.len == 0 || val_name.len == 0 {
        return ast.Type(0), ast.Type(0)
    }
    key_type := g.table.find_type(key_name)
    val_type := g.table.find_type(val_name)
    return g.unwrap_generic(g.recheck_concrete_type(key_type)), g.unwrap_generic(g.recheck_concrete_type(val_type))
}

fn (mut g Gen) resolved_call_like_expr_type(expr ast.Expr) ast.Type {
    match expr {
        ast.CallExpr {
            resolved := g.resolve_return_type(expr)
            if resolved != ast.void_type {
                return g.unwrap_generic(g.recheck_concrete_type(resolved)).clear_option_and_result()
            }
        }
        ast.PostfixExpr {
            resolved := g.resolved_call_like_expr_type(expr.expr)
            if resolved != 0 {
                return g.unwrap_generic(resolved).clear_option_and_result()
            }
        }
        ast.UnsafeExpr {
            return g.resolved_call_like_expr_type(expr.expr)
        }
        else {}
    }

    return 0
}

// resolved_expr_type recomputes the concrete type for expr nodes that can keep
// stale generic metadata across concrete rechecks/codegen.
fn (mut g Gen) resolved_or_block_value_type(or_expr ast.OrExpr) ast.Type {
    if or_expr.stmts.len == 0 {
        return 0
    }
    last_or_stmt := or_expr.stmts.last()
    if last_or_stmt is ast.ExprStmt && last_or_stmt.typ != ast.void_type {
        resolved_or_type := g.resolved_expr_type(last_or_stmt.expr, last_or_stmt.typ)
        if resolved_or_type != 0 && resolved_or_type != ast.void_type {
            return g.unwrap_generic(g.recheck_concrete_type(resolved_or_type))
        }
    }
    return 0
}

// resolve_selector_smartcast_type resolves the final smartcast type for a
// selector expression in generic contexts. When a field like `val.field` has
// nested smartcasts (e.g., option unwrap then sumtype variant), the scope
// stores these smartcasts but they may reference stale types from a previous
// generic instantiation. This function re-resolves them using current concrete
// types to determine the correct final type.
fn (mut g Gen) resolve_selector_smartcast_type(node ast.SelectorExpr) ast.Type {
    scope := g.file.scope.innermost(node.pos.pos)
    field := scope.find_struct_field(node.expr.str(), node.expr_type, node.field_name)
    if field != unsafe { nil } && field.smartcasts.len > 0 {
        smartcast_type := field.smartcasts.last()
        field_unwrapped_type := field.orig_type.clear_option_and_result()
        if field.orig_type.has_option_or_result() && !smartcast_type.has_option_or_result()
            && smartcast_type == field_unwrapped_type {
            left_default := if node.expr_type != 0 { node.expr_type } else { field.struct_type }
            left_type := g.resolved_expr_type(node.expr, left_default)
            resolved_field_type := g.resolved_selector_field_type(node, left_type)
            if resolved_field_type != 0 {
                return resolved_field_type.clear_option_and_result()
            }
        }
        resolved_sc := g.unwrap_generic(g.recheck_concrete_type(g.exposed_smartcast_type(field.orig_type,
            smartcast_type, field.is_mut)))
        if resolved_sc != 0 {
            return resolved_sc
        }
    }
    return 0
}

fn (mut g Gen) resolved_selector_field_type(node ast.SelectorExpr, receiver_type ast.Type) ast.Type {
    if receiver_type == 0 {
        return 0
    }
    sym := g.table.sym(g.unwrap_generic(receiver_type))
    if field := g.table.find_field_with_embeds(sym, node.field_name) {
        mut field_type := field.typ
        match sym.info {
            ast.Struct, ast.Interface, ast.SumType {
                mut generic_names := sym.info.generic_types.map(g.table.sym(it).name)
                mut concrete_types := sym.info.concrete_types.clone()
                if concrete_types.len == 0 && sym.generic_types.len == generic_names.len
                    && sym.generic_types != sym.info.generic_types {
                    concrete_types = sym.generic_types.clone()
                }
                mut source_field_type := field.typ
                if sym.info.parent_type.has_flag(.generic) {
                    parent_sym := g.table.sym(sym.info.parent_type)
                    if parent_field := g.table.find_field_with_embeds(parent_sym, node.field_name) {
                        source_field_type = parent_field.typ
                        match parent_sym.info {
                            ast.Struct, ast.Interface, ast.SumType {
                                generic_names =
                                    parent_sym.info.generic_types.map(g.table.sym(it).name)
                            }
                            else {}
                        }
                    }
                }
                if generic_names.len == concrete_types.len && concrete_types.len > 0 {
                    mut muttable := unsafe { &ast.Table(g.table) }
                    resolved_field_type := muttable.unwrap_generic_type_ex(source_field_type,
                        generic_names, concrete_types, true)
                    if resolved_field_type != source_field_type {
                        field_type = resolved_field_type
                    } else {
                        if converted_field_type := muttable.convert_generic_type(source_field_type,
                            generic_names, concrete_types)
                        {
                            field_type = converted_field_type
                        }
                    }
                }
            }
            ast.GenericInst {
                parent_sym := g.table.sym(ast.new_type(sym.info.parent_idx))
                mut source_field_type := field.typ
                if parent_field := g.table.find_field_with_embeds(parent_sym, node.field_name) {
                    source_field_type = parent_field.typ
                }
                match parent_sym.info {
                    ast.Struct, ast.Interface, ast.SumType {
                        generic_names := parent_sym.info.generic_types.map(g.table.sym(it).name)
                        if generic_names.len == sym.info.concrete_types.len
                            && sym.info.concrete_types.len > 0 {
                            mut muttable := unsafe { &ast.Table(g.table) }
                            resolved_field_type := muttable.unwrap_generic_type_ex(source_field_type,
                                generic_names, sym.info.concrete_types, true)
                            if resolved_field_type != source_field_type {
                                field_type = resolved_field_type
                            } else {
                                if converted_field_type := muttable.convert_generic_type(source_field_type,
                                    generic_names, sym.info.concrete_types)
                                {
                                    field_type = converted_field_type
                                }
                            }
                        }
                    }
                    else {}
                }
            }
            else {}
        }

        $if trace_ci_fixes ? {
            if g.file.path.contains('binary_search_tree.v') && node.expr is ast.Ident
                && node.expr.name == 'tree' {
                eprintln('resolved selector ${node.expr.name}.${node.field_name} left=${g.table.type_to_str(receiver_type)} field=${g.table.type_to_str(field.typ)} final=${g.table.type_to_str(field_type)} expr_typ=${g.table.type_to_str(node.typ)}')
            }
        }
        return g.unwrap_generic(g.recheck_concrete_type(field_type))
    }
    return 0
}

fn (mut g Gen) resolved_expr_type(expr ast.Expr, default_typ ast.Type) ast.Type {
    match expr {
        ast.ParExpr {
            return g.resolved_expr_type(expr.expr, default_typ)
        }
        ast.CTempVar {
            if expr.typ != 0 {
                return g.unwrap_generic(g.recheck_concrete_type(expr.typ))
            }
            return g.resolved_expr_type(expr.orig, default_typ)
        }
        ast.Ident {
            if expr.obj is ast.Var {
                if expr.obj.typ != 0 && expr.obj.generic_typ == 0 && !expr.obj.is_inherited
                    && !expr.obj.is_unwrapped && !expr.obj.is_assignment_smartcast
                    && !expr.obj.is_or && expr.obj.orig_type == ast.no_type
                    && expr.obj.smartcasts.len == 0 && expr.obj.ct_type_var == .no_comptime
                    && !g.has_current_generic_context() && !g.has_active_call_generic_context() {
                    if g.type_is_known_concrete(expr.obj.typ) {
                        return expr.obj.typ
                    }
                }
                if g.cur_fn != unsafe { nil } && g.cur_fn.is_method
                    && expr.name == g.cur_fn.receiver.name {
                    // In generic contexts, prefer resolving from the receiver declaration
                    // since scope types may be stale from a previous checker instantiation
                    if g.cur_concrete_types.len > 0 && (g.cur_fn.receiver.typ.has_flag(.generic)
                        || g.type_has_unresolved_generic_parts(g.cur_fn.receiver.typ)) {
                        resolved_receiver_type :=
                            g.unwrap_generic(g.recheck_concrete_type(g.cur_fn.receiver.typ))
                        if resolved_receiver_type != 0 {
                            return resolved_receiver_type
                        }
                    }
                    scope_type := g.resolved_scope_var_type(expr)
                    if scope_type != 0 {
                        return scope_type
                    }
                    resolved_receiver_type :=
                        g.unwrap_generic(g.recheck_concrete_type(g.cur_fn.receiver.typ))
                    if resolved_receiver_type != 0 {
                        return resolved_receiver_type
                    }
                }
                if g.cur_fn != unsafe { nil } && g.cur_concrete_types.len > 0
                    && expr.obj.expr is ast.Ident {
                    ident_expr := expr.obj.expr as ast.Ident
                    if ident_expr.or_expr.kind != .absent {
                        resolved_or_type := g.resolved_or_block_value_type(ident_expr.or_expr)
                        if resolved_or_type != 0 {
                            return resolved_or_type
                        }
                    }
                }
                if expr.obj.ct_type_var == .generic_param {
                    resolved := g.resolve_current_fn_generic_param_type(expr.name)
                    if resolved != 0 {
                        return g.unwrap_generic(g.recheck_concrete_type(resolved))
                    }
                }
                // In generic contexts, if the variable has smartcasts with generic
                // types (preserved in node.obj), resolve from those instead of
                // relying on scope types which may be stale from a different
                // generic instantiation.
                if g.cur_fn != unsafe { nil } && g.cur_concrete_types.len > 0
                    && expr.obj.smartcasts.len > 0 && expr.obj.smartcasts.any(it.has_flag(.generic)
                    || g.type_has_unresolved_generic_parts(it)) {
                    obj_smartcast_type := g.exposed_smartcast_type(expr.obj.orig_type,
                        expr.obj.smartcasts.last(), expr.obj.is_mut)
                    resolved_sc := g.unwrap_generic(g.recheck_concrete_type(obj_smartcast_type))
                    if resolved_sc != 0 {
                        return resolved_sc
                    }
                }
                scope_type := g.resolved_scope_var_type(expr)
                if scope_type != 0 && !scope_type.has_flag(.generic)
                    && !g.type_has_unresolved_generic_parts(scope_type) {
                    if !expr.obj.is_arg
                        || (g.cur_fn != unsafe { nil } && g.cur_concrete_types.len > 0) {
                        // For generic_var in generic contexts, prefer expression-based
                        // resolution first (scope types may be stale from a previous
                        // instantiation), but fall back to scope type if expr resolution
                        // fails.
                        if g.cur_fn != unsafe { nil } && g.cur_concrete_types.len > 0
                            && expr.obj.ct_type_var == .generic_var
                            && expr.obj.typ.has_flag(.generic) {
                            // Try expression-based resolution first
                            if expr.obj.expr !is ast.EmptyExpr && !(expr.obj.expr is ast.Ident
                                && expr.obj.expr.name == expr.name) {
                                resolved := g.resolved_expr_type(expr.obj.expr, expr.obj.typ)
                                if resolved != 0 {
                                    return g.unwrap_generic(resolved)
                                }
                            }
                        }
                        // In generic contexts, scope types may be stale from a previous
                        // checker instantiation. If the variable's init expression is a
                        // struct init whose type name matches a generic parameter, re-resolve
                        // using the current concrete types.
                        if g.cur_fn != unsafe { nil } && g.cur_concrete_types.len > 0
                            && expr.obj.expr is ast.StructInit {
                            generic_names := g.current_fn_generic_names()
                            struct_init_typ_str := expr.obj.expr.typ_str.all_after_last('.')
                            idx := generic_names.index(struct_init_typ_str)
                            if idx >= 0 && idx < g.cur_concrete_types.len {
                                return g.cur_concrete_types[idx]
                            }
                        }
                        return scope_type
                    }
                }
                if expr.obj.expr !is ast.EmptyExpr
                    && (expr.obj.ct_type_var == .generic_var || expr.obj.typ.has_flag(.generic)
                    || g.type_has_unresolved_generic_parts(expr.obj.typ)
                    || ((g.cur_fn != unsafe { nil } && g.cur_concrete_types.len > 0)
                    && expr.obj.expr !in [ast.IntegerLiteral, ast.FloatLiteral, ast.StringLiteral, ast.BoolLiteral, ast.CharLiteral])) {
                    if !(expr.obj.expr is ast.Ident && expr.obj.expr.name == expr.name) {
                        mut resolved := g.resolved_expr_type(expr.obj.expr, expr.obj.typ)
                        if resolved != 0 {
                            resolved = g.unwrap_generic(g.recheck_concrete_type(resolved))
                            if expr.obj.typ != 0 {
                                resolved_obj_type :=
                                    g.unwrap_generic(g.recheck_concrete_type(expr.obj.typ))
                                if resolved_obj_type != 0
                                    && !g.type_has_unresolved_generic_parts(resolved_obj_type)
                                    && resolved.has_option_or_result()
                                    && resolved.clear_option_and_result() == resolved_obj_type {
                                    return resolved_obj_type
                                }
                            }
                            if g.type_has_unresolved_generic_parts(resolved) {
                                call_like_type := g.resolved_call_like_expr_type(expr.obj.expr)
                                if call_like_type != 0 && !call_like_type.has_flag(.generic)
                                    && !g.type_has_unresolved_generic_parts(call_like_type) {
                                    return call_like_type
                                }
                            }
                            return g.unwrap_generic(resolved)
                        }
                    }
                }
                if expr.obj.ct_type_var != .no_comptime && expr.obj.ct_type_var != .generic_param {
                    ctyp := g.type_resolver.get_type(expr)
                    if ctyp != ast.void_type {
                        return g.unwrap_generic(ctyp)
                    }
                }
            }
            if g.cur_fn != unsafe { nil } && g.cur_fn.generic_names.len > 0
                && g.cur_concrete_types.len > 0 {
                resolved := g.resolve_current_fn_generic_param_type(expr.name)
                if resolved != 0 {
                    return g.unwrap_generic(g.recheck_concrete_type(resolved))
                }
            }
            if expr.obj is ast.Var && expr.obj.typ != 0 {
                resolved_obj_type := g.unwrap_generic(g.recheck_concrete_type(expr.obj.typ))
                if resolved_obj_type != 0 && (expr.obj.is_arg || expr.obj.typ.has_flag(.generic)
                    || g.type_has_unresolved_generic_parts(expr.obj.typ)) {
                    return resolved_obj_type
                }
            }
            scope_type := g.resolved_scope_var_type(expr)
            if scope_type != 0 && expr.obj is ast.Var
                && (expr.obj.is_unwrapped || expr.obj.orig_type != 0 || expr.obj.smartcasts.len > 0) {
                return scope_type
            }
            default_resolved_type := g.unwrap_generic(g.recheck_concrete_type(default_typ))
            resolver_type := g.unwrap_generic(g.recheck_concrete_type(g.type_resolver.get_type_or_default(expr,
                default_typ)))
            if resolver_type != 0 && !g.type_has_unresolved_generic_parts(resolver_type)
                && (resolver_type != default_resolved_type || (expr.obj is ast.Var
                && (expr.obj.is_unwrapped || expr.obj.orig_type != 0
                || expr.obj.smartcasts.len > 0))) {
                return resolver_type
            }
            if scope_type != 0 {
                return scope_type
            }
        }
        ast.SelectorExpr {
            // If this selector has been smart-cast in the current scope (e.g.
            // `if mut w.face is X { ... w.face ... }`), use the smart-cast type
            // rather than the field's declared type.
            smartcast_typ := g.resolve_selector_smartcast_type(expr)
            if smartcast_typ != 0 {
                return smartcast_typ
            }
            left_default := if expr.expr_type != 0 { expr.expr_type } else { default_typ }
            left_type := g.recheck_concrete_type(g.resolved_expr_type(expr.expr, left_default))
            if left_type != 0 {
                mut resolved_type := g.resolved_selector_field_type(expr, left_type)
                if resolved_type != 0 {
                    if expr.or_block.kind != .absent {
                        resolved_type = resolved_type.clear_option_and_result()
                    }
                    return resolved_type
                }
            }
            if expr.typ != 0 {
                mut resolved_type := g.unwrap_generic(g.recheck_concrete_type(expr.typ))
                if expr.or_block.kind != .absent {
                    resolved_type = resolved_type.clear_option_and_result()
                }
                return resolved_type
            }
        }
        ast.IndexExpr {
            left_default := if expr.left_type != 0 { expr.left_type } else { default_typ }
            left_type := g.recheck_concrete_type(g.resolved_expr_type(expr.left, left_default))
            if left_type != 0 {
                if expr.index is ast.RangeExpr {
                    mut slice_type := ast.Type(0)
                    if expr.left is ast.Ident {
                        resolved_left_type :=
                            g.resolve_current_fn_generic_param_type(expr.left.name)
                        if resolved_left_type != 0 {
                            slice_type = g.unwrap_generic(resolved_left_type)
                        }
                    }
                    if slice_type == 0 {
                        slice_type = g.unwrap_generic(left_type)
                    }
                    // Slicing returns a new array by value; strip pointer
                    // from mut params.
                    slice_type = slice_type.set_nr_muls(0)
                    // Slicing a fixed array yields a dynamic array.
                    slice_sym := g.table.final_sym(slice_type)
                    if slice_sym.info is ast.ArrayFixed {
                        return ast.new_type(g.table.find_or_register_array(slice_sym.info.elem_type))
                    }
                    return slice_type
                }
                if expr.left is ast.Ident {
                    resolved_value_type :=
                        g.resolve_current_fn_generic_param_value_type(expr.left.name)
                    if resolved_value_type != 0 {
                        return g.unwrap_generic(resolved_value_type)
                    }
                }
                value_type :=
                    g.recheck_concrete_type(g.table.value_type(g.unwrap_generic(left_type)))
                if value_type != 0 {
                    return g.unwrap_generic(value_type)
                }
                if expr.typ != 0 && !expr.typ.has_flag(.generic)
                    && !g.type_has_unresolved_generic_parts(expr.typ) {
                    return g.unwrap_generic(expr.typ)
                }
            }
        }
        ast.InfixExpr {
            if expr.op in [.eq, .ne, .gt, .ge, .lt, .le, .logical_or, .and, .key_in, .not_in, .key_is,
                .not_is] {
                return ast.bool_type
            }
            // In generic contexts, promoted_type may be stale from a different
            // checker instantiation pass. Compute from operand types instead.
            if expr.promoted_type != 0 && !expr.promoted_type.has_flag(.generic)
                && !g.type_has_unresolved_generic_parts(expr.promoted_type)
                && (g.cur_fn == unsafe { nil } || g.cur_concrete_types.len == 0) {
                return g.unwrap_generic(g.recheck_concrete_type(expr.promoted_type))
            }
            left_default := if expr.left_type != 0 { expr.left_type } else { default_typ }
            right_default := if expr.right_type != 0 { expr.right_type } else { default_typ }
            left_type := g.resolved_expr_type(expr.left, left_default)
            right_type := g.resolved_expr_type(expr.right, right_default)
            if expr.op in [.plus, .minus, .mul, .power, .div, .mod] {
                if left_type == right_type && left_type != 0
                    && left_type !in [ast.int_literal_type, ast.float_literal_type] {
                    return g.unwrap_generic(left_type)
                }
                promoted := g.type_resolver.promote_type(g.unwrap_generic(left_type),
                    g.unwrap_generic(right_type))
                if promoted != ast.void_type {
                    return g.unwrap_generic(promoted)
                }
            }
            if expr.op in [.left_shift, .right_shift, .amp, .pipe, .xor] && left_type != 0 {
                return g.unwrap_generic(left_type)
            }
        }
        ast.IfGuardExpr {
            // A variable bound by an `if x := opt() {` guard stores the whole
            // `IfGuardExpr` as its init expression. Resolve from the guard's source
            // expression so the variable's type follows the current generic
            // instantiation, instead of a stale type baked from a different one
            // (see issue #27205). Only single-var guards map to one value type.
            if expr.vars.len == 1 {
                resolved := g.resolved_expr_type(expr.expr, if expr.expr_type != 0 {
                    expr.expr_type
                } else {
                    default_typ
                })
                if resolved != 0 {
                    return g.unwrap_generic(g.recheck_concrete_type(resolved)).clear_option_and_result()
                }
            }
        }
        ast.IfExpr {
            inferred_typ := g.infer_if_expr_type(expr)
            if inferred_typ != 0 && inferred_typ != ast.void_type {
                return inferred_typ
            }
        }
        ast.MatchExpr {
            inferred_typ := g.infer_match_expr_type(expr)
            if inferred_typ != 0 && inferred_typ != ast.void_type {
                return inferred_typ
            }
        }
        ast.CallExpr {
            if expr.kind == .type_name {
                return ast.string_type
            }
            if expr.kind == .type_idx {
                return ast.int_type
            }
            resolved := g.resolve_return_type(expr)
            if resolved != ast.void_type {
                return if expr.or_block.kind == .absent {
                    g.unwrap_generic(g.recheck_concrete_type(resolved))
                } else {
                    g.unwrap_generic(g.recheck_concrete_type(resolved)).clear_option_and_result()
                }
            }
            // When resolve_return_type fails (e.g. fn field call where no method exists),
            // try resolving from return_type_generic using receiver generic type names.
            // This handles cases like Procedure[T,U].handle() calling p.function(p.value)
            // where return_type is contaminated from the last checker pass but
            // return_type_generic preserves the original generic return type (!U).
            if expr.return_type_generic != 0 && expr.return_type_generic.has_flag(.generic)
                && g.cur_fn != unsafe { nil } && g.cur_fn.is_method
                && g.cur_fn.receiver.typ.has_flag(.generic) && g.cur_concrete_types.len > 0 {
                receiver_generic_names := g.table.generic_type_names(g.cur_fn.receiver.typ)
                if receiver_generic_names.len == g.cur_concrete_types.len {
                    if gen_type := g.table.convert_generic_type(expr.return_type_generic,
                        receiver_generic_names, g.cur_concrete_types)
                    {
                        if !gen_type.has_flag(.generic) {
                            return if expr.or_block.kind == .absent {
                                gen_type
                            } else {
                                gen_type.clear_option_and_result()
                            }
                        }
                    }
                }
            }
            if expr.return_type != 0 {
                return if expr.or_block.kind == .absent {
                    g.unwrap_generic(g.recheck_concrete_type(expr.return_type))
                } else {
                    g.unwrap_generic(g.recheck_concrete_type(expr.return_type)).clear_option_and_result()
                }
            }
        }
        ast.ComptimeCall {
            if expr.kind == .method && g.comptime.comptime_for_method != unsafe { nil } {
                sym := g.table.sym(g.unwrap_generic(expr.left_type))
                if m := sym.find_method(g.comptime.comptime_for_method.name) {
                    return m.return_type
                }
            }
        }
        ast.ComptimeSelector {
            if expr.is_method {
                ctyp := g.type_resolver.get_comptime_selector_type(expr, ast.void_type)
                if ctyp != ast.void_type {
                    return g.unwrap_generic(ctyp)
                }
                if expr.typ != ast.void_type && expr.typ != 0 {
                    return g.unwrap_generic(expr.typ)
                }
            } else if expr.typ_key != '' {
                ctyp := g.type_resolver.get_ct_type_or_default(expr.typ_key, default_typ)
                if ctyp != ast.void_type {
                    return g.unwrap_generic(ctyp)
                }
            }
            if expr.left_type != 0 {
                return g.unwrap_generic(expr.left_type)
            }
        }
        ast.CastExpr {
            if expr.typ != 0 {
                return g.unwrap_generic(g.recheck_concrete_type(expr.typ))
            }
        }
        ast.ArrayInit {
            base_array_typ := if expr.generic_typ != 0 { expr.generic_typ } else { expr.typ }
            base_elem_typ := if expr.generic_elem_type != 0 {
                expr.generic_elem_type
            } else {
                expr.elem_type
            }
            if g.cur_fn != unsafe { nil } && g.cur_concrete_types.len > 0 && base_array_typ != 0
                && expr.exprs.len > 0 && !expr.is_fixed {
                array_type := g.unwrap_generic(g.recheck_concrete_type(base_array_typ))
                if g.table.final_sym(array_type).kind == .array {
                    mut inferred_elem_type := ast.void_type
                    for i, elem_expr in expr.exprs {
                        mut default_elem_type := base_elem_typ
                        if default_elem_type == 0 {
                            default_elem_type = g.table.value_type(array_type)
                        }
                        if inferred_elem_type != ast.void_type {
                            default_elem_type = inferred_elem_type
                        }
                        mut resolved_elem_type := ast.void_type
                        if elem_expr is ast.Ident {
                            resolved_elem_type = g.resolved_scope_var_type(elem_expr)
                        }
                        if resolved_elem_type == ast.void_type {
                            expr_default_type := if expr.expr_types.len > i
                                && expr.expr_types[i] != 0 {
                                expr.expr_types[i]
                            } else {
                                default_elem_type
                            }
                            resolved_elem_type = g.unwrap_generic(g.recheck_concrete_type(g.resolved_expr_type(elem_expr,
                                expr_default_type)))
                        }
                        if resolved_elem_type != 0 && resolved_elem_type != ast.void_type {
                            inferred_elem_type = resolved_elem_type
                        }
                    }
                    if inferred_elem_type != ast.void_type {
                        return g.table.find_or_register_array(g.unwrap_generic(inferred_elem_type))
                    }
                }
            }
            if base_array_typ != 0 {
                return g.unwrap_generic(g.recheck_concrete_type(base_array_typ))
            }
        }
        ast.StructInit {
            // For `T{}` where T is a generic parameter, typ_str preserves the
            // original name (e.g. 'main.T') even after the type has been resolved
            // to a concrete type. Use it to look up the current concrete type.
            if expr.typ_str.len > 0 && g.cur_fn != unsafe { nil } && g.cur_concrete_types.len > 0 {
                generic_names := g.current_fn_generic_names()
                short_name := expr.typ_str.all_after_last('.')
                idx := generic_names.index(short_name)
                if idx >= 0 && idx < g.cur_concrete_types.len {
                    return g.cur_concrete_types[idx]
                }
            }
            // In generic contexts, use generic_typ to allow resolution via
            // recheck_concrete_type/unwrap_generic only when the struct init type
            // itself still has unresolved generic parts (short syntax or generic flag).
            // For explicitly typed inits (e.g. LinkedList[StructFieldInfo]{}),
            // preserve expr.typ to avoid incorrectly substituting the inner struct's
            // generic parameter with the enclosing function's concrete type.
            base_struct_typ := if expr.generic_typ != 0 && g.cur_fn != unsafe { nil }
                && g.cur_concrete_types.len > 0 {
                if expr.is_short_syntax || expr.typ.has_flag(.generic) || expr.typ == ast.void_type {
                    expr.generic_typ
                } else {
                    expr.typ
                }
            } else if expr.typ != 0 {
                expr.typ
            } else {
                expr.generic_typ
            }
            if base_struct_typ != 0 {
                return g.unwrap_generic(g.recheck_concrete_type(base_struct_typ))
            }
        }
        ast.MapInit {
            if expr.typ != 0 {
                return g.unwrap_generic(g.recheck_concrete_type(expr.typ))
            }
        }
        ast.AsCast {
            return g.unwrap_generic(g.recheck_concrete_type(expr.typ))
        }
        ast.UnsafeExpr {
            return g.resolved_expr_type(expr.expr, default_typ)
        }
        ast.PrefixExpr {
            right_default := if expr.right_type != 0 { expr.right_type } else { default_typ }
            inner_type := g.resolved_expr_type(expr.right, right_default)
            return match expr.op {
                .amp {
                    // When the inner expr is an auto-deref var (e.g. mut param),
                    // codegen skips emitting & since the var is already a pointer.
                    // Don't add .ref() to match.
                    if expr.right.is_auto_deref_var() {
                        g.unwrap_generic(inner_type)
                    } else {
                        g.unwrap_generic(inner_type).ref()
                    }
                }
                .mul {
                    resolved_inner_type := g.unwrap_generic(inner_type)
                    if resolved_inner_type.is_ptr() {
                        resolved_inner_type.deref()
                    } else {
                        resolved_right_type :=
                            g.unwrap_generic(g.recheck_concrete_type(right_default))
                        if resolved_right_type.is_ptr() {
                            resolved_right_type.deref()
                        } else {
                            resolved_inner_type
                        }
                    }
                }
                .arrow {
                    right_sym := g.table.final_sym(g.unwrap_generic(inner_type))
                    if right_sym.kind == .chan {
                        g.unwrap_generic(right_sym.chan_info().elem_type)
                    } else {
                        g.unwrap_generic(inner_type)
                    }
                }
                else {
                    g.unwrap_generic(inner_type)
                }
            }
        }
        ast.PostfixExpr {
            inner_default := if expr.typ != 0 { expr.typ } else { default_typ }
            inner_type := g.resolved_expr_type(expr.expr, inner_default)
            return if expr.op == .question {
                mut resolved_postfix_type := g.unwrap_generic(inner_type)
                if resolved_postfix_type != 0 && g.table.sym(resolved_postfix_type).kind == .alias {
                    unaliased_postfix_type := g.table.unaliased_type(resolved_postfix_type)
                    if unaliased_postfix_type.has_option_or_result() {
                        resolved_postfix_type = g.unwrap_generic(unaliased_postfix_type)
                    }
                }
                resolved_postfix_type.clear_option_and_result()
            } else {
                g.unwrap_generic(inner_type)
            }
        }
        else {}
    }

    resolved := g.type_resolver.get_type_or_default(expr, default_typ)
    if resolved != 0 {
        return g.unwrap_generic(resolved)
    }
    return g.unwrap_generic(default_typ)
}

struct Type {
    // typ is the original type
    typ ast.Type        @[required]
    sym &ast.TypeSymbol @[required]
    // unaliased is `typ` once aliased have been resolved
    // it may not contain information such as flags and nr_muls
    unaliased     ast.Type        @[required]
    unaliased_sym &ast.TypeSymbol @[required]
}

// unwrap returns the following variants of a type:
// * generics unwrapped
// * alias unwrapped
fn (mut g Gen) unwrap(typ ast.Type) Type {
    no_generic := g.unwrap_generic(typ)
    no_generic_sym := g.table.sym(no_generic)
    if no_generic_sym.kind != .alias {
        return Type{
            typ:           no_generic
            sym:           no_generic_sym
            unaliased:     no_generic
            unaliased_sym: no_generic_sym
        }
    }
    return Type{
        typ:           no_generic
        sym:           no_generic_sym
        unaliased:     no_generic_sym.parent_idx
        unaliased_sym: g.table.sym(ast.idx_to_type(no_generic_sym.parent_idx))
    }
}

// generate function variable definition, e.g. `void (*var_name) (int, string)`
fn (mut g Gen) fn_var_signature(var_type ast.Type, return_type ast.Type, arg_types []ast.Type, var_name string) string {
    if var_type.has_flag(.option) || var_type.has_flag(.result) {
        return '${g.styp(var_type)} ${c_fn_name(var_name)}'
    }
    ret_styp := g.styp(return_type)
    nr_muls := var_type.nr_muls()
    mut sig := '${ret_styp} (${'*'.repeat(nr_muls + 1)}${c_fn_name(var_name)}) ('
    for j, arg_typ in arg_types {
        arg_sym := g.table.sym(arg_typ)
        if arg_sym.info is ast.FnType {
            func := arg_sym.info.func
            arg_sig := g.fn_var_signature(arg_typ, func.return_type, func.params.map(it.typ), '')
            sig += arg_sig
        } else {
            arg_styp := g.styp(arg_typ)
            sig += arg_styp
        }
        if j < arg_types.len - 1 {
            sig += ', '
        }
    }
    sig += ')'
    return sig
}

// generate anon fn cname, e.g. `anon_fn_void_int_string`, `anon_fn_void_int_ptr_string`
fn (mut g Gen) anon_fn_cname(return_type ast.Type, arg_types []ast.Type) string {
    ret_styp := g.styp(return_type).replace('*', '_ptr')
    mut sig := 'anon_fn_${ret_styp}_'
    for j, arg_typ in arg_types {
        arg_sym := g.table.sym(arg_typ)
        if arg_sym.info is ast.FnType {
            sig += g.anon_fn_cname(arg_sym.info.func.return_type,
                arg_sym.info.func.params.map(it.typ))
        } else {
            sig += g.styp(arg_typ).replace('*', '_ptr')
        }
        if j < arg_types.len - 1 {
            sig += '_'
        }
    }
    return sig
}

// escape quotes for string
fn escape_quotes(val string) string {
    bs := '\\'
    unescaped_val := val.replace('${bs}${bs}', '\x01').replace_each([
        "${bs}'",
        "'",
        '${bs}"',
        '"',
    ])
    return unescaped_val.replace_each(['\x01', '${bs}${bs}', "'", "${bs}'", '"', '${bs}"'])
}

@[inline]
fn (mut g Gen) dot_or_ptr(val_type ast.Type) string {
    return if val_type.has_flag(.shared_f) {
        '->val.'
    } else if val_type.is_ptr() {
        '->'
    } else {
        '.'
    }
}

fn (mut g Gen) unwrap_option_type(typ ast.Type, name string, is_auto_heap bool) {
    styp := g.base_type(typ)
    if is_auto_heap {
        g.write('(*(${styp}*)${name}->data)')
    } else {
        type_sym := g.table.sym(typ)
        if type_sym.kind == .alias {
            // Alias to Option type
            parent_typ := (type_sym.info as ast.Alias).parent_type
            if parent_typ.has_flag(.option) {
                g.write('*((${g.base_type(parent_typ)}*)')
            }
            g.write('(*(${styp}*)${name}.data)')
            if parent_typ.has_flag(.option) {
                g.write('.data)')
            }
        } else if typ.has_flag(.option_mut_param_t) {
            g.write('(*(${styp}*)${name}->data)')
        } else {
            g.write('(*(${styp}*)${name}.data)')
        }
    }
}