From ba31a3c0c8c37f8ed3352787cd9a23d2941d2b1d Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Fri, 12 Jun 2026 05:58:07 +0300
Subject: [PATCH] checker: require common fields for match aggregates (#27428)

---
 vlib/v/ast/table.v                            | 31 +++++++++++++++++--
 vlib/v/checker/checker.v                      |  2 +-
 .../tests/match_sumtype_multiple_types.out    | 14 +++++++++
 3 files changed, 43 insertions(+), 4 deletions(-)

diff --git a/vlib/v/ast/table.v b/vlib/v/ast/table.v
index c78b797ed..0f2fe99aa 100644
--- a/vlib/v/ast/table.v
+++ b/vlib/v/ast/table.v
@@ -824,12 +824,37 @@ pub fn (t &Table) find_field_from_embeds(sym &TypeSymbol, field_name string) !(S
 			return error('ambiguous field `${field_name}`')
 		}
 	} else if sym.info is Aggregate {
+		mut found_once := false
+		mut new_field := StructField{}
+		mut found_embed_types := []Type{}
 		for typ in sym.info.types {
 			agg_sym := t.sym(typ)
-			field, embed_types := t.find_field_from_embeds(agg_sym, field_name) or { continue }
-			if embed_types.len > 0 {
-				return field, embed_types
+			mut field := StructField{}
+			mut embed_types := []Type{}
+			if type_field := t.find_field(agg_sym, field_name) {
+				field = type_field
+			} else {
+				field, embed_types = t.find_field_from_embeds(agg_sym, field_name) or {
+					return error('type `${t.type_to_str(typ)}` has no field or method `${field_name}`')
+				}
+				if found_embed_types.len == 0 {
+					found_embed_types = embed_types.clone()
+				}
+			}
+			if !found_once {
+				found_once = true
+				new_field = field
+			} else if new_field.typ != field.typ {
+				return error('field `${t.type_to_str(typ)}.${field_name}` type is different')
 			}
+			new_field = StructField{
+				...new_field
+				is_mut: new_field.is_mut && field.is_mut
+				is_pub: new_field.is_pub && field.is_pub
+			}
+		}
+		if found_once {
+			return new_field, found_embed_types
 		}
 	} else if sym.info is Alias {
 		unalias_sym := t.sym(sym.info.parent_type)
diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index c1d7ddcc8..5f198b62f 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -3172,7 +3172,7 @@ fn (mut c Checker) selector_expr(mut node ast.SelectorExpr) ast.Type {
 			} else {
 				first_err := err
 				has_field = false
-				if final_sym.kind in [.aggregate, .sum_type] {
+				if final_sym.kind == .sum_type {
 					if variant_typ, variant_field, variant_embed_types := c.table.find_single_field_variant(final_sym,
 						field_name)
 					{
diff --git a/vlib/v/checker/tests/match_sumtype_multiple_types.out b/vlib/v/checker/tests/match_sumtype_multiple_types.out
index 0a84394db..a156c11e1 100644
--- a/vlib/v/checker/tests/match_sumtype_multiple_types.out
+++ b/vlib/v/checker/tests/match_sumtype_multiple_types.out
@@ -1,3 +1,17 @@
+vlib/v/checker/tests/match_sumtype_multiple_types.vv:26:13: error: type `Charlie` has no field or method `char`
+   24 |     match l {
+   25 |         Alfa, Charlie {
+   26 |             assert l.char == `a`
+      |                      ~~~~
+   27 |             assert l.letter() == 'a'
+   28 |         }
+vlib/v/checker/tests/match_sumtype_multiple_types.vv:26:11: error: assert can be used only with `bool` expressions, but found `void` instead
+   24 |     match l {
+   25 |         Alfa, Charlie {
+   26 |             assert l.char == `a`
+      |                    ~~~~~~~~~~~~~
+   27 |             assert l.letter() == 'a'
+   28 |         }
 vlib/v/checker/tests/match_sumtype_multiple_types.vv:27:13: error: unknown method: `Charlie.letter`
    25 |         Alfa, Charlie {
    26 |             assert l.char == `a`
-- 
2.39.5