cgen: include ast.ComptimeSelector in fixed array checks (fix #25767) (#25777)

Author: dy-tea

vlib/v/gen/c/assign.v

@@ -532,7 +532,7 @@ fn (mut g Gen) assign_stmt(node_ ast.AssignStmt) {
 		unaliased_right_sym := g.table.final_sym(unwrapped_val_type)
 		unaliased_left_sym := g.table.final_sym(g.unwrap_generic(var_type))
 		is_fixed_array_var := unaliased_right_sym.kind == .array_fixed && val !is ast.ArrayInit
-			&& (val in [ast.Ident, ast.IndexExpr, ast.CallExpr, ast.SelectorExpr, ast.DumpExpr, ast.InfixExpr]
+			&& (val in [ast.Ident, ast.IndexExpr, ast.CallExpr, ast.SelectorExpr, ast.ComptimeSelector, ast.DumpExpr, ast.InfixExpr]
 			|| (val is ast.CastExpr && val.expr !is ast.ArrayInit)
 			|| (val is ast.PrefixExpr && val.op == .arrow)
 			|| (val is ast.UnsafeExpr && val.expr in [ast.SelectorExpr, ast.Ident, ast.CallExpr]))
@@ -568,7 +568,8 @@ fn (mut g Gen) assign_stmt(node_ ast.AssignStmt) {
 				} else {
 					g.write('{${styp} _ = ')
 				}
-				if val in [ast.MatchExpr, ast.IfExpr] && unaliased_right_sym.info is ast.ArrayFixed {
+				if (val in [ast.MatchExpr, ast.IfExpr, ast.ComptimeSelector] || is_fixed_array_var)
+					&& unaliased_right_sym.info is ast.ArrayFixed {
 					tmp_var := g.expr_with_var(val, var_type, false)
 					g.fixed_array_var_init(tmp_var, false, unaliased_right_sym.info.elem_type,
 						unaliased_right_sym.info.size)

vlib/v/tests/comptime/comptime_for_fixed_array_field_test.v

@@ -0,0 +1,86 @@
+struct StructWithFixedArrays {
+	number u64
+	bytes  [8]u8
+	floats [4]f32
+	name   string
+	matrix [2][3]int
+}
+
+fn collect_field_info[T](t T) []string {
+	mut info := []string{}
+	$for f in T.fields {
+		v := t.$(f.name)
+		info << '${f.name}: ${v}'
+	}
+	return info
+}
+
+fn count_accessible_fields[T](t T) int {
+	mut count := 0
+	$for f in T.fields {
+		_ := t.$(f.name)
+		count++
+	}
+	return count
+}
+
+fn test_fixed_array_field_access() {
+	test := StructWithFixedArrays{
+		number: 42
+		bytes:  [u8(1), 2, 3, 4, 5, 6, 7, 8]!
+		floats: [f32(1.0), 2.0, 3.0, 4.0]!
+		name:   'test'
+		matrix: [[1, 2, 3]!, [4, 5, 6]!]!
+	}
+
+	info := collect_field_info(test)
+
+	assert info.len == 5
+	assert info[0].contains('number: 42')
+	assert info[1].contains('bytes: [1, 2, 3, 4, 5, 6, 7, 8]')
+	assert info[2].contains('floats: [1.0, 2.0, 3.0, 4.0]')
+	assert info[3].contains('name: test')
+	assert info[4].contains('matrix: [[1, 2, 3], [4, 5, 6]]')
+}
+
+fn test_nested_fixed_arrays() {
+	test := StructWithFixedArrays{
+		number: 100
+		bytes:  [u8(10), 20, 30, 40, 50, 60, 70, 80]!
+		floats: [f32(0.1), 0.2, 0.3, 0.4]!
+		name:   'nested'
+		matrix: [[10, 20, 30]!, [40, 50, 60]!]!
+	}
+
+	assert count_accessible_fields(test) == 5
+}
+
+fn test_fixed_array_comptime_iteration() {
+	test := StructWithFixedArrays{
+		number: 999
+		bytes:  [u8(0), 1, 2, 3, 4, 5, 6, 7]!
+		floats: [f32(1.1), 2.2, 3.3, 4.4]!
+		name:   'iteration'
+		matrix: [[100, 200, 300]!, [400, 500, 600]!]!
+	}
+
+	mut field_names := []string{}
+	mut field_values := []string{}
+
+	$for f in StructWithFixedArrays.fields {
+		field_names << f.name
+		val := test.$(f.name)
+		field_values << '${val}'
+	}
+	assert field_names.len == 5
+	assert field_values.len == 5
+
+	assert 'number' in field_names
+	assert 'bytes' in field_names
+	assert 'floats' in field_names
+	assert 'name' in field_names
+	assert 'matrix' in field_names
+
+	assert field_values[0].contains('999')
+	assert field_values[3].contains('iteration')
+}