cgen: fix several issues with autofree(fix vlang#20635)

vlib/v/gen/c/cgen.v

@@ -2873,7 +2873,8 @@ fn (mut g Gen) get_ternary_name(name string) string {
 }
 
 fn (mut g Gen) gen_clone_assignment(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.CallExpr, ast.MatchExpr, ast.IfExpr, ast.IndexExpr,
+ ast.ParExpr, ast.UnsafeExpr] {
  return false
  }
  right_sym := g.table.sym(typ)
@@ -2978,6 +2979,11 @@ fn (mut g Gen) autofree_scope_vars2(scope &ast.Scope, start_pos int, end_pos int
  // TODO: free options
  continue
  }
+ is_result := obj.typ.has_flag(.result)
+ if is_result {
+ // TODO: free result
+ continue
+ }
  g.autofree_variable(obj)
  }
  else {}
@@ -5348,6 +5354,14 @@ fn (mut g Gen) return_stmt(node ast.Return) {
  node.types[0].has_flag(.option)
  }
  }
+ // autofree before `return`
+ // set free_parent_scopes to true, since all variables defined in parent
+ // scopes need to be freed before the return
+ if g.is_autofree {
+ if expr0 is ast.Ident {
+ g.returned_var_name = expr0.name
+ }
+ }
  if fn_return_is_option && !expr_type_is_opt && return_sym.name != c.option_name {
  styp := g.base_type(fn_ret_type)
  g.writeln('${ret_typ} ${tmpvar};')
@@ -5408,15 +5422,6 @@ fn (mut g Gen) return_stmt(node ast.Return) {
  g.writeln('return ${tmpvar};')
  return
  }
- // autofree before `return`
- // set free_parent_scopes to true, since all variables defined in parent
- // scopes need to be freed before the return
- if g.is_autofree {
- expr := node.exprs[0]
- if expr is ast.Ident {
- g.returned_var_name = expr.name
- }
- }
  // free := g.is_autofree && !g.is_builtin_mod // node.exprs[0] is ast.CallExpr
  // Create a temporary variable for the return expression
  if use_tmp_var || !g.is_builtin_mod {

vlib/v/tests/autofree_test.v

@@ -0,0 +1,58 @@
+// vtest vflags: -autofree
+
+fn return_array_with_result() ![]int {
+ mut arr := []int{}
+ arr << 123
+ return arr
+}
+
+fn return_array_with_option() ?[]int {
+ mut arr := []int{}
+ arr << 123
+ return arr
+}
+
+fn return_strng(s string) string {
+ return s
+}
+
+fn test_main() {
+ arr1 := return_array_with_result()!
+ assert arr1 == [123]
+ arr2 := return_array_with_option()?
+ assert arr2 == [123]
+
+ // test ident
+ str1 := '${'123'}abc'
+ str2 := str1
+ assert str2 == '123abc'
+
+ // test CallExpr
+ str3 := return_strng(str1)
+ assert str3 == '123abc'
+
+ // test MatchExpr
+ str4 := match true {
+ true {
+ str1
+ }
+ else {
+ str1
+ }
+ }
+ assert str4 == '123abc'
+
+ // test IfExpr
+ str5 := if true { str1 } else { str1 }
+ assert str5 == '123abc'
+
+ // test ParExpr
+ // vfmt off
+ str6 := (str1)
+ // vfmt on
+ assert str6 == '123abc'
+
+ // test UnsafeExpr
+ str7 := unsafe { str1 }
+ assert str7 == '123abc'
+}