autofree: handle tmp vars in for loops

vlib/v/ast/ast.v

@@ -369,8 +369,9 @@ pub mut:
 	pos             token.Position
 	is_used         bool
 	is_changed      bool // to detect mutable vars that are never changed
-	is_or           bool // `x := foo() or { ... }`
 	// (for setting the position after the or block for autofree)
+	is_or           bool // `x := foo() or { ... }`
+	is_tmp          bool // for tmp for loop vars, so that autofree can skip them
 }
 
 // used for smartcasting only

vlib/v/gen/cgen.v

@@ -2100,9 +2100,14 @@ fn (mut g Gen) autofree_scope_vars2(scope &ast.Scope, start_pos int, end_pos int
 					continue
 				}
 				if obj.is_or {
-					g.writeln('// skipping `or{}` var "$obj.name"')
 					// Skip vars inited with the `or {}`, since they are generated
 					// after the or block in C.
+					g.writeln('// skipping `or{}` var "$obj.name"')
+					continue
+				}
+				if obj.is_tmp {
+					// Skip for loop vars
+					g.writeln('// skipping tmp var "$obj.name"')
 					continue
 				}
 				// if var.typ == 0 {

vlib/v/parser/for.v

@@ -105,6 +105,7 @@ fn (mut p Parser) for_stmt() ast.Stmt {
 				name: key_var_name
 				typ: table.int_type
 				pos: key_var_pos
+				is_tmp: true
 			})
 		} else if p.scope.known_var(val_var_name) {
 			p.error('redefinition of value iteration variable `$val_var_name`')
@@ -130,6 +131,7 @@ fn (mut p Parser) for_stmt() ast.Stmt {
 				name: val_var_name
 				typ: table.int_type
 				pos: val_var_pos
+				is_tmp: true
 			})
 			if key_var_name.len > 0 {
 				p.error_with_pos('cannot declare index variable with range `for`', key_var_pos)
@@ -141,6 +143,7 @@ fn (mut p Parser) for_stmt() ast.Stmt {
 				name: val_var_name
 				pos: val_var_pos
 				is_mut: val_is_mut
+				is_tmp: true
 			})
 		}
 		p.inside_for = false

vlib/v/tests/valgrind/1.strings_and_arrays.v

@@ -291,6 +291,11 @@ fn free_before_break() {
 			continue
 		}
 	}
+	x := ['1', '2', '3']
+	for n in x {
+		f := 'f'
+		println('$n => $f')
+	}
 }
 
 struct User {