parser,gen: fix `arr << map[key] using map_get_and_set_1, leading to double free

vlib/builtin/array_test.v

@@ -1092,7 +1092,9 @@ fn test_push_arr_string_free() {
 	mut lines := ['hi']
 	s := 'a' + 'b'
 	lines << s
-	s.free() // make sure the data in the array is valid after freeing the string
+	// make sure the data in the array is valid after freeing the string
+	unsafe { s.free() }
+	//
 	println(lines)
 	assert lines.len == 2
 	assert lines[0] == 'hi'

vlib/v/ast/ast.v

@@ -110,12 +110,12 @@ pub:
 pub struct SelectorExpr {
 pub:
 	pos        token.Position
-	expr       Expr // expr.field_name
 	field_name string
 	is_mut     bool // is used for the case `if mut ident.selector is MyType {`, it indicates if the root ident is mutable
 	mut_pos    token.Position
 	next_token token.Kind
 pub mut:
+	expr            Expr       // expr.field_name
 	expr_type       table.Type // type of `Foo` in `Foo.bar`
 	typ             table.Type // type of the entire thing (`Foo.bar`)
 	name_type       table.Type // T in `T.name` or typeof in `typeof(expr).name`
@@ -609,12 +609,15 @@ pub mut:
 pub struct IndexExpr {
 pub:
 	pos     token.Position
-	left    Expr
 	index   Expr // [0], RangeExpr [start..end] or map[key]
 	or_expr OrExpr
 pub mut:
+	left      Expr
 	left_type table.Type // array, map, fixed array
 	is_setter bool
+	is_map    bool
+	is_array  bool
+	is_farray bool
 }
 
 pub struct IfExpr {
@@ -1543,3 +1546,13 @@ pub fn (expr Expr) is_mut_ident() bool {
 	}
 	return false
 }
+
+// helper for dealing with `m[k1][k2][k3][k3] = value`
+pub fn (mut lx IndexExpr) recursive_mapset_is_setter(val bool) {
+	lx.is_setter = val
+	if mut lx.left is IndexExpr {
+		if lx.left.is_map {
+			lx.left.recursive_mapset_is_setter(val)
+		}
+	}
+}

vlib/v/checker/checker.v

@@ -2695,6 +2695,12 @@ pub fn (mut c Checker) assign_stmt(mut assign_stmt ast.AssignStmt) {
 				}
 			}
 			else {
+				if mut left is ast.IndexExpr {
+					// eprintln('>>> left.is_setter: ${left.is_setter:10} | left.is_map: ${left.is_map:10} | left.is_array: ${left.is_array:10}')
+					if left.is_map && left.is_setter {
+						left.recursive_mapset_is_setter(true)
+					}
+				}
 				if is_decl {
 					c.error('non-name `$left` on left side of `:=`', left.position())
 				}
@@ -5223,6 +5229,18 @@ pub fn (mut c Checker) index_expr(mut node ast.IndexExpr) table.Type {
 	mut typ := c.expr(node.left)
 	node.left_type = typ
 	typ_sym := c.table.get_final_type_symbol(typ)
+	match typ_sym.kind {
+		.map {
+			node.is_map = true
+		}
+		.array {
+			node.is_array = true
+		}
+		.array_fixed {
+			node.is_farray = true
+		}
+		else {}
+	}
 	if typ_sym.kind !in [.array, .array_fixed, .string, .map] && !typ.is_ptr()
 		&& typ !in [table.byteptr_type, table.charptr_type] && !typ.has_flag(.variadic) {
 		c.error('type `$typ_sym.name` does not support indexing', node.pos)

vlib/v/gen/c/cgen.v

@@ -4373,7 +4373,11 @@ fn (mut g Gen) index_expr(node ast.IndexExpr) {
 						g.is_array_set = true
 						g.write('map_set_1(')
 					} else {
-						g.write('(*(($elem_type_str*)map_get_and_set_1(')
+						if node.is_setter {
+							g.write('(*(($elem_type_str*)map_get_and_set_1(')
+						} else {
+							g.write('(*(($elem_type_str*)map_get_1(')
+						}
 					}
 					if !left_is_ptr || node.left_type.has_flag(.shared_f) {
 						g.write('&')
@@ -4409,7 +4413,11 @@ fn (mut g Gen) index_expr(node ast.IndexExpr) {
 					|| g.inside_map_index
 					|| (g.is_assign_lhs && !g.is_array_set && get_and_set_types) {
 					zero := g.type_default(info.value_type)
-					g.write('(*($elem_type_str*)map_get_and_set_1(')
+					if node.is_setter {
+						g.write('(*($elem_type_str*)map_get_and_set_1(')
+					} else {
+						g.write('(*($elem_type_str*)map_get_1(')
+					}
 					if !left_is_ptr {
 						g.write('&')
 					}

vlib/v/parser/pratt.v

@@ -348,6 +348,9 @@ pub fn (mut p Parser) expr_with_left(left ast.Expr, precedence int, is_stmt_iden
 			p.next()
 			right := p.expr(precedence - 1)
 			pos.update_last_line(p.prev_tok.line_nr)
+			if mut node is ast.IndexExpr {
+				node.recursive_mapset_is_setter(true)
+			}
 			node = ast.InfixExpr{
 				left: node
 				right: right
@@ -381,6 +384,9 @@ pub fn (mut p Parser) expr_with_left(left ast.Expr, precedence int, is_stmt_iden
 				p.error_with_pos('$p.tok must be on the same line as the previous token',
 					p.tok.position())
 			}
+			if mut node is ast.IndexExpr {
+				node.recursive_mapset_is_setter(true)
+			}
 			node = ast.PostfixExpr{
 				op: p.tok.kind
 				expr: node

vlib/v/tests/nested_map_test.v

@@ -1,14 +1,4 @@
-struct Foo {
-mut:
-	name string
-}
-
-fn test_nested_maps() {
-	if true {
-	}
-	//
-	else {
-	}
+fn test_map_of_map() {
 	mut x := map[string]map[string]int{}
 	x['a'] = map[string]int{}
 	assert x['a']['b'] == 0
@@ -16,6 +6,9 @@ fn test_nested_maps() {
 	assert x['a']['b'] == 5
 	x['a']['b'] = 7
 	assert x['a']['b'] == 7
+}
+
+fn test_map_of_map_of_map() {
 	mut y := map[string]map[string]map[string]int{}
 	y['a'] = map[string]map[string]int{}
 	y['a']['b'] = map[string]int{}
@@ -24,9 +17,18 @@ fn test_nested_maps() {
 	assert y['a']['b']['c'] == 5
 	y['a']['b']['c'] = 7
 	assert y['a']['b']['c'] == 7
-	mut foos := map[string]map[string]Foo{}
-	foos['a']['b'] = Foo{'bar'}
-	assert foos['a']['b'].name == 'bar'
-	foos['a']['b'].name = 'baz'
-	assert foos['a']['b'].name == 'baz'
+}
+
+struct Foo {
+mut:
+	name string
+}
+
+fn test_map_of_map_to_struct() {
+	mut foos := map[string]map[string]Foo{}
+	foos['zza']['zzb'] = Foo{'bar'}
+	assert foos['zza']['zzb'].name == 'bar'
+	//
+	foos['zza']['zzb'].name = 'baz'
+	assert foos['zza']['zzb'].name == 'baz'
 }