autofree: remove duplicate free() calls after a return statement, triggered by error string interpolation (#26592)

Author: esquerbatua

vlib/v/gen/c/cgen.v

@@ -2232,19 +2232,22 @@ fn is_noreturn_callexpr(expr ast.Expr) bool {
 }
 
 // stmts_with_tmp_var is used in `if` or `match` branches.
-// It returns true, if the last statement was a `return`
+// It returns true, if the last statement was a `return` or `branch`
 fn (mut g Gen) stmts_with_tmp_var(stmts []ast.Stmt, tmp_var string) bool {
 	g.indent++
 	if g.inside_ternary > 0 {
 		g.write('(')
 	}
 	expected_cast_type := g.expected_cast_type
+	// Track if last statement was return or branch (for autofree, both skip scope cleanup)
 	mut last_stmt_was_return := false
 	for i, stmt in stmts {
 		if i == stmts.len - 1 {
 			g.expected_cast_type = expected_cast_type
 			if stmt is ast.Return {
 				last_stmt_was_return = true
+			} else if stmt is ast.BranchStmt {
+				last_stmt_was_return = true
 			}
 		}
 		if i == stmts.len - 1 && tmp_var != '' {
@@ -2402,7 +2405,7 @@ fn (mut g Gen) stmts_with_tmp_var(stmts []ast.Stmt, tmp_var string) bool {
 	if g.inside_ternary > 0 {
 		g.write2('', ')')
 	}
-	if g.is_autofree && !g.inside_vweb_tmpl && stmts.len > 0 {
+	if g.is_autofree && !g.inside_vweb_tmpl && stmts.len > 0 && !last_stmt_was_return {
 		// use the first stmt to get the scope
 		stmt := stmts[0]
 		if stmt !is ast.FnDecl && g.inside_ternary == 0 {

vlib/v/slow_tests/valgrind/autofree_or_block_string_interp.v

@@ -0,0 +1,17 @@
+// vtest vflags: -autofree
+// Test that autofree doesn't generate duplicate free statements
+// after return in or blocks with string interpolation
+
+fn main() {
+	x := 'test'
+	_ := somefn() or {
+		msg := 'fail'
+		println('Error: ${msg}')
+		return
+	}
+	println('Success')
+}
+
+fn somefn() !int {
+	return error('test')
+}

vlib/v/slow_tests/valgrind/valgrind_test.v

@@ -26,6 +26,7 @@ const skip_compile_files = [
 ]
 
 const skip_valgrind_files = [
+	'vlib/v/slow_tests/valgrind/autofree_or_block_string_interp.v',
 	'vlib/v/slow_tests/valgrind/struct_field.v',
 	'vlib/v/slow_tests/valgrind/fn_returning_string_param.v',
 	'vlib/v/slow_tests/valgrind/fn_with_return_should_free_local_vars.v',