checker: fix map with reference value (#16990)

vlib/v/checker/assign.v

@@ -109,7 +109,9 @@ fn (mut c Checker) assign_stmt(mut node ast.AssignStmt) {
 			if left in [ast.Ident, ast.SelectorExpr] {
 				c.prevent_sum_type_unwrapping_once = true
 			}
+			c.inside_left_assign = true
 			left_type = c.expr(left)
+			c.inside_left_assign = false
 			c.expected_type = c.unwrap_generic(left_type)
 		}
 		if node.right_types.len < node.left.len { // first type or multi return types added above

vlib/v/checker/checker.v

@@ -111,7 +111,8 @@ mut:
 	inside_println_arg               bool
 	inside_decl_rhs                  bool
 	inside_if_guard                  bool // true inside the guard condition of `if x := opt() {}`
-	comptime_call_pos                int  // needed for correctly checking use before decl for templates
+	inside_left_assign               bool
+	comptime_call_pos                int // needed for correctly checking use before decl for templates
 	goto_labels                      map[string]ast.GotoLabel // to check for unused goto labels
 }
 
@@ -3815,7 +3816,8 @@ fn (mut c Checker) index_expr(mut node ast.IndexExpr) ast.Type {
 			node.pos)
 	}
 
-	if !c.inside_unsafe && !c.is_builtin_mod && typ_sym.kind == .map && node.or_expr.stmts.len == 0 {
+	if !c.inside_unsafe && !c.is_builtin_mod && !c.inside_if_guard && !c.inside_left_assign
+		&& typ_sym.kind == .map && node.or_expr.stmts.len == 0 {
 		elem_type := c.table.value_type(typ)
 		if elem_type.is_real_pointer() {
 			c.note('accessing a pointer map value requires an `or{}` block outside `unsafe`',

vlib/v/tests/map_reference_value_test.v

@@ -0,0 +1,17 @@
+struct Foo {
+	bar string
+}
+
+fn test_map_reference_value() {
+	m1 := map[string]&Foo{}
+	if e := m1['bar'] {
+		println(e.bar)
+	}
+	println(m1)
+
+	mut m2 := map[string]&Foo{}
+	m2['bar'] = &Foo{}
+	println(m2)
+
+	assert true
+}