checker: disallow taking the address of consts with int literal values (#19160)

vlib/v/checker/assign.v

@@ -264,7 +264,17 @@ fn (mut c Checker) assign_stmt(mut node ast.AssignStmt) {
 		node.left_types << left_type
 		match mut left {
 			ast.Ident {
-				if left.kind == .blank_ident {
+				if (is_decl || left.kind == .blank_ident) && left_type.is_ptr()
+					&& mut right is ast.PrefixExpr && right.right_type == ast.int_literal_type_idx {
+					if mut right.right is ast.Ident && right.right.obj is ast.ConstField {
+						const_name := right.right.name.all_after_last('.')
+						const_val := (right.right.obj as ast.ConstField).expr
+						c.add_error_detail('Specify the type for the constant value. Example:')
+						c.add_error_detail('         `const ${const_name} = int(${const_val})`')
+						c.error('cannot assign a pointer to a constant with an integer literal value',
+							right.right.pos)
+					}
+				} else if left.kind == .blank_ident {
 					left_type = right_type
 					node.left_types[i] = right_type
 					if node.op !in [.assign, .decl_assign] {

vlib/v/checker/tests/assign_const_ptr_int_literal_err.out

@@ -0,0 +1,9 @@
+vlib/v/checker/tests/assign_const_ptr_int_literal_err.vv:4:8: error: cannot assign a pointer to a constant with an integer literal value
+    2 | 
+    3 | fn main() {
+    4 |     b := &a
+      |           ^
+    5 |     dump(b)
+    6 | }
+Details: Specify the type for the constant value. Example:
+         `const a = int(3)`

vlib/v/checker/tests/assign_const_ptr_int_literal_err.vv

@@ -0,0 +1,6 @@
+const a = 3
+
+fn main() {
+	b := &a
+	dump(b)
+}

vlib/v/checker/tests/blank_ident_const_ptr_int_literal_err.out

@@ -0,0 +1,8 @@
+vlib/v/checker/tests/blank_ident_const_ptr_int_literal_err.vv:4:8: error: cannot assign a pointer to a constant with an integer literal value
+    2 | 
+    3 | fn main() {
+    4 |     _ := &a
+      |           ^
+    5 | }
+Details: Specify the type for the constant value. Example:
+         `const a = int(3)`

vlib/v/checker/tests/blank_ident_const_ptr_int_literal_err.vv

@@ -0,0 +1,5 @@
+const a = 3
+
+fn main() {
+	_ := &a
+}