cgen,autofree: fix method chaining generating invalid c code (fix #9094) (#25315)

Author: dy-tea

vlib/v/gen/c/assign.v

@@ -219,8 +219,14 @@ fn (mut g Gen) assign_stmt(node_ ast.AssignStmt) {
 	}
 	// Free the old value assigned to this string var (only if it's `str = [new value]`
 	// or `x.str = [new value]` )
-	mut af := g.is_autofree && !g.is_builtin_mod && node.op == .assign && node.left_types.len == 1
-		&& node.left[0] in [ast.Ident, ast.SelectorExpr]
+	mut af := g.is_autofree && !g.is_builtin_mod && !g.is_autofree_tmp && node.op == .assign
+		&& node.left_types.len == 1 && node.left[0] in [ast.Ident, ast.SelectorExpr]
+	if af && node.right.len == 1 && node.right[0] is ast.CallExpr {
+		call_expr := node.right[0] as ast.CallExpr
+		if call_expr.is_method && call_expr.left is ast.CallExpr {
+			af = false
+		}
+	}
 	mut sref_name := ''
 	mut type_to_free := ''
 	if af {

vlib/v/gen/c/cgen.v

@@ -102,6 +102,7 @@ mut:
 	is_shared                 bool // for initialization of hidden mutex in `[rw]shared` literals
 	is_vlines_enabled         bool // is it safe to generate #line directives when -g is passed
 	is_autofree               bool // false, inside the bodies of fns marked with [manualfree], otherwise === g.pref.autofree
+	is_autofree_tmp           bool // when generating autofree temporary variables
 	is_builtin_mod            bool
 	is_json_fn                bool // inside json.encode()
 	is_js_call                bool // for handling a special type arg #1 `json.decode(User, ...)`

vlib/v/gen/c/fn.v

@@ -2345,7 +2345,20 @@ fn (mut g Gen) autofree_call_pregen(node ast.CallExpr) {
 			})
 			s = 'string ${t} = '
 		}
-		s += g.expr_string(arg.expr)
+		g.is_autofree_tmp = true
+		pos_before := g.out.len
+
+		old_is_autofree := g.is_autofree
+		if arg.expr is ast.CallExpr && arg.expr.is_method && arg.expr.left is ast.CallExpr {
+			g.is_autofree = false
+		}
+
+		g.expr(arg.expr)
+		expr_code := g.out.cut_to(pos_before).trim_space()
+
+		g.is_autofree = old_is_autofree
+		g.is_autofree_tmp = false
+		s += expr_code
 		s += ';// new af2 pre'
 		g.strs_to_free0 << s
 		// This tmp arg var will be freed with the rest of the vars at the end of the scope.

vlib/v/gen/c/testdata/autofree_method_chain.c.must_have

@@ -0,0 +1,11 @@
+void main__Test_set_tags(main__Test* t, string tags) {
+string _arg_expr_split_0_169 = builtin__string_trim_space(builtin__string_replace(builtin__string_to_lower(tags), _S(","), _S(" ")));// new af2 pre/* inserted before */
+		t->tags = builtin__string_split(/*af receiver arg*/_arg_expr_split_0_169, _S(" "));
+	builtin__string_free(&_arg_expr_split_0_169); // autofreed var main false
+}
+VV_LOC void main__main(void) {
+	main__Test test = ((main__Test){.tags = builtin____new_array(0, 0, sizeof(string)),});
+	main__Test_set_tags(&test, _S("Hello, World"));
+	string _t1 = Array_string_str(test.tags); builtin__println(_t1); builtin__string_free(&_t1);
+	;
+}

vlib/v/gen/c/testdata/autofree_method_chain.out

@@ -0,0 +1 @@
+['hello', '', 'world']

vlib/v/gen/c/testdata/autofree_method_chain.vv

@@ -0,0 +1,15 @@
+// vtest vflags: -autofree
+pub struct Test {
+mut:
+	tags []string
+}
+
+pub fn (mut t Test) set_tags(tags string) {
+	t.tags = tags.to_lower().replace(',', ' ').trim_space().split(' ')
+}
+
+fn main() {
+	mut test := Test{}
+	test.set_tags('Hello, World')
+	println(test.tags)
+}