From df8f8ae4d1612becd70ee0d387d09f6973081802 Mon Sep 17 00:00:00 2001
From: shove <shove@163.com>
Date: Tue, 16 Jan 2024 02:08:31 +0800
Subject: [PATCH] checker: fix checking give const map as default or init value
 to struct fields (fix #20512) (#20546)

---
 vlib/v/checker/struct.v                          | 16 ++++++++++++++++
 .../struct_field_init_and_default_is_map_err.out | 14 ++++++++++++++
 .../struct_field_init_and_default_is_map_err.vv  | 14 ++++++++++++++
 3 files changed, 44 insertions(+)
 create mode 100644 vlib/v/checker/tests/struct_field_init_and_default_is_map_err.out
 create mode 100644 vlib/v/checker/tests/struct_field_init_and_default_is_map_err.vv

diff --git a/vlib/v/checker/struct.v b/vlib/v/checker/struct.v
index d2d4161b6..92d3cd63e 100644
--- a/vlib/v/checker/struct.v
+++ b/vlib/v/checker/struct.v
@@ -101,6 +101,15 @@ fn (mut c Checker) struct_decl(mut node ast.StructDecl) {
 			if field.has_default_expr {
 				c.expected_type = field.typ
 				field.default_expr_typ = c.expr(mut field.default_expr)
+				// disallow map `mut a = b`
+				field_sym := c.table.sym(field.typ)
+				expr_sym := c.table.sym(field.default_expr_typ)
+				if field_sym.kind == .map && expr_sym.kind == .map && field.default_expr.is_lvalue()
+					&& field.is_mut
+					&& (!field.default_expr_typ.is_ptr() || field.default_expr is ast.Ident) {
+					c.error('cannot copy map: call `clone` method (or use a reference)',
+						field.default_expr.pos())
+				}
 				for mut symfield in struct_sym.info.fields {
 					if symfield.name == field.name {
 						symfield.default_expr_typ = field.default_expr_typ
@@ -606,6 +615,13 @@ fn (mut c Checker) struct_init(mut node ast.StructInit, is_field_zero_struct_ini
 					c.error('allocate `${got_type_sym.name}` on the heap for use in other functions',
 						init_field.pos)
 				}
+				// disallow `mut a: b`, when b is const map
+				if exp_type_sym.kind == .map && got_type_sym.kind == .map && !got_type.is_ptr()
+					&& field_info.is_mut
+					&& (init_field.expr is ast.Ident && init_field.expr.obj is ast.ConstField) {
+					c.error('cannot assign a const map to mut struct field, call `clone` method (or use a reference)',
+						init_field.expr.pos())
+				}
 				if exp_type_sym.kind == .array && got_type_sym.kind == .array {
 					if init_field.expr is ast.IndexExpr
 						&& (init_field.expr as ast.IndexExpr).left is ast.Ident
diff --git a/vlib/v/checker/tests/struct_field_init_and_default_is_map_err.out b/vlib/v/checker/tests/struct_field_init_and_default_is_map_err.out
new file mode 100644
index 000000000..07ddb73d2
--- /dev/null
+++ b/vlib/v/checker/tests/struct_field_init_and_default_is_map_err.out
@@ -0,0 +1,14 @@
+vlib/v/checker/tests/struct_field_init_and_default_is_map_err.vv:7:25: error: cannot copy map: call `clone` method (or use a reference)
+    5 | struct Foo {
+    6 | mut:
+    7 |     field map[string]int = const_map
+      |                            ~~~~~~~~~
+    8 | }
+    9 |
+vlib/v/checker/tests/struct_field_init_and_default_is_map_err.vv:12:10: error: cannot assign a const map to mut struct field, call `clone` method (or use a reference)
+   10 | fn main() {
+   11 |     _ = Foo{
+   12 |         field: const_map
+      |                ~~~~~~~~~
+   13 |     }
+   14 | }
diff --git a/vlib/v/checker/tests/struct_field_init_and_default_is_map_err.vv b/vlib/v/checker/tests/struct_field_init_and_default_is_map_err.vv
new file mode 100644
index 000000000..93935ac11
--- /dev/null
+++ b/vlib/v/checker/tests/struct_field_init_and_default_is_map_err.vv
@@ -0,0 +1,14 @@
+const const_map = {
+	'key': 4
+}
+
+struct Foo {
+mut:
+	field map[string]int = const_map
+}
+
+fn main() {
+	_ = Foo{
+		field: const_map
+	}
+}
-- 
2.39.5