From 777460dfd3f7cf551cb57ac9a6f29831aa85f164 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Sat, 30 May 2026 23:42:35 +0300
Subject: [PATCH] cgen: clone comptime selector assignments (#27295)

---
 vlib/v/checker/assign.v                       |  7 +++-
 .../tests/comptime_selector_map_copy_err.out  |  7 ++++
 .../tests/comptime_selector_map_copy_err.vv   | 20 ++++++++++++
 vlib/v/gen/c/cgen.v                           |  2 +-
 ...tofree_comptime_selector_clone.c.must_have |  2 ++
 .../autofree_comptime_selector_clone.out      |  1 +
 .../autofree_comptime_selector_clone.vv       | 32 +++++++++++++++++++
 .../comptime_selector_map_move_test.v         | 27 ++++++++++++++++
 8 files changed, 96 insertions(+), 2 deletions(-)
 create mode 100644 vlib/v/checker/tests/comptime_selector_map_copy_err.out
 create mode 100644 vlib/v/checker/tests/comptime_selector_map_copy_err.vv
 create mode 100644 vlib/v/gen/c/testdata/autofree_comptime_selector_clone.c.must_have
 create mode 100644 vlib/v/gen/c/testdata/autofree_comptime_selector_clone.out
 create mode 100644 vlib/v/gen/c/testdata/autofree_comptime_selector_clone.vv
 create mode 100644 vlib/v/tests/comptime/comptime_selector_map_move_test.v

diff --git a/vlib/v/checker/assign.v b/vlib/v/checker/assign.v
index b6f931682..94561a954 100644
--- a/vlib/v/checker/assign.v
+++ b/vlib/v/checker/assign.v
@@ -881,8 +881,13 @@ or use an explicit `unsafe{ a[..] }`, if you do not want a copy of the slice.',
 				}
 			}
 		}
+		right_is_lvalue := if right is ast.ComptimeSelector {
+			right.left.is_lvalue()
+		} else {
+			right.is_lvalue()
+		}
 		if left_sym.kind == .map && is_assign && right_sym.kind == .map && !c.inside_unsafe
-			&& !left.is_blank_ident() && right.is_lvalue() && right !is ast.ComptimeSelector
+			&& !left.is_blank_ident() && right_is_lvalue
 			&& (!right_type.is_ptr() || (right is ast.Ident && assign_expr_is_auto_deref(right))) {
 			// Do not allow `a = b`
 			c.error('cannot copy map: call `move` or `clone` method (or use a reference)',
diff --git a/vlib/v/checker/tests/comptime_selector_map_copy_err.out b/vlib/v/checker/tests/comptime_selector_map_copy_err.out
new file mode 100644
index 000000000..d043e9cdb
--- /dev/null
+++ b/vlib/v/checker/tests/comptime_selector_map_copy_err.out
@@ -0,0 +1,7 @@
+vlib/v/checker/tests/comptime_selector_map_copy_err.vv:8:18: error: cannot copy map: call `move` or `clone` method (or use a reference)
+    6 |     $for field in T.fields {
+    7 |         $if field.unaliased_typ is map[string]string {
+    8 |             values := val.$(field.name)
+      |                           ~~~~~~~~~~~~~
+    9 |             _ = values
+   10 |         }
diff --git a/vlib/v/checker/tests/comptime_selector_map_copy_err.vv b/vlib/v/checker/tests/comptime_selector_map_copy_err.vv
new file mode 100644
index 000000000..0b6551ba8
--- /dev/null
+++ b/vlib/v/checker/tests/comptime_selector_map_copy_err.vv
@@ -0,0 +1,20 @@
+struct Item {
+	values map[string]string
+}
+
+fn process[T](val T) {
+	$for field in T.fields {
+		$if field.unaliased_typ is map[string]string {
+			values := val.$(field.name)
+			_ = values
+		}
+	}
+}
+
+fn main() {
+	process(Item{
+		values: {
+			'a': 'b'
+		}
+	})
+}
diff --git a/vlib/v/gen/c/cgen.v b/vlib/v/gen/c/cgen.v
index 57a27d013..a15ab02ba 100644
--- a/vlib/v/gen/c/cgen.v
+++ b/vlib/v/gen/c/cgen.v
@@ -5569,7 +5569,7 @@ fn (mut g Gen) get_ternary_name(name string) string {
 }
 
 fn (mut g Gen) gen_clone_assignment(var_type ast.Type, val ast.Expr, typ ast.Type, add_eq bool) bool {
-	if val !in [ast.Ident, ast.SelectorExpr] {
+	if val !in [ast.Ident, ast.SelectorExpr, ast.ComptimeSelector] {
 		return false
 	}
 	right_sym := g.table.sym(typ)
diff --git a/vlib/v/gen/c/testdata/autofree_comptime_selector_clone.c.must_have b/vlib/v/gen/c/testdata/autofree_comptime_selector_clone.c.must_have
new file mode 100644
index 000000000..03ced7047
--- /dev/null
+++ b/vlib/v/gen/c/testdata/autofree_comptime_selector_clone.c.must_have
@@ -0,0 +1,2 @@
+builtin__string_clone_static(val.name)
+builtin__array_clone_static_to_depth(val.tags, 1)
diff --git a/vlib/v/gen/c/testdata/autofree_comptime_selector_clone.out b/vlib/v/gen/c/testdata/autofree_comptime_selector_clone.out
new file mode 100644
index 000000000..9766475a4
--- /dev/null
+++ b/vlib/v/gen/c/testdata/autofree_comptime_selector_clone.out
@@ -0,0 +1 @@
+ok
diff --git a/vlib/v/gen/c/testdata/autofree_comptime_selector_clone.vv b/vlib/v/gen/c/testdata/autofree_comptime_selector_clone.vv
new file mode 100644
index 000000000..86f2aeac6
--- /dev/null
+++ b/vlib/v/gen/c/testdata/autofree_comptime_selector_clone.vv
@@ -0,0 +1,32 @@
+// vtest vflags: -autofree
+struct Item {
+	name string
+	tags []string
+}
+
+fn process[T](val T) string {
+	mut result := ''
+	$for field in T.fields {
+		$if field.unaliased_typ is string {
+			name := val.$(field.name)
+			result += name
+		} $else $if field.unaliased_typ is []string {
+			arr := val.$(field.name)
+			for tag in arr {
+				result += tag
+			}
+		}
+	}
+	return result
+}
+
+fn main() {
+	item := Item{
+		name: 'test'
+		tags: ['a', 'b', 'c']
+	}
+	assert process(item) == 'testabc'
+	assert item.name == 'test'
+	assert item.tags == ['a', 'b', 'c']
+	println('ok')
+}
diff --git a/vlib/v/tests/comptime/comptime_selector_map_move_test.v b/vlib/v/tests/comptime/comptime_selector_map_move_test.v
new file mode 100644
index 000000000..dd8cd46a4
--- /dev/null
+++ b/vlib/v/tests/comptime/comptime_selector_map_move_test.v
@@ -0,0 +1,27 @@
+struct MapHolder {
+	values map[string]string
+}
+
+fn make_map_holder() MapHolder {
+	return MapHolder{
+		values: {
+			'a': 'b'
+		}
+	}
+}
+
+fn first_map_from_temporary[T]() map[string]string {
+	$for field in T.fields {
+		$if field.unaliased_typ is map[string]string {
+			values := make_map_holder().$(field.name)
+			return values
+		}
+	}
+	return {}
+}
+
+fn test_comptime_selector_map_move_from_temporary() {
+	assert first_map_from_temporary[MapHolder]() == {
+		'a': 'b'
+	}
+}
-- 
2.39.5