From 1dc5d36724a796d8bbfb8192633a89cf00975b5b Mon Sep 17 00:00:00 2001
From: Swastik Baranwal <swstkbaranwal@gmail.com>
Date: Tue, 30 Jan 2024 22:33:26 +0530
Subject: [PATCH] checker: disallow `(x) := 10` (#20695)

---
 vlib/v/checker/assign.v                              | 5 +++++
 vlib/v/checker/tests/par_expr_decl_assign_err.out    | 5 +++++
 vlib/v/checker/tests/par_expr_decl_assign_err.vv     | 3 +++
 vlib/v/checker/tests/prefix_expr_decl_assign_err.out | 6 ++++++
 4 files changed, 19 insertions(+)
 create mode 100644 vlib/v/checker/tests/par_expr_decl_assign_err.out
 create mode 100644 vlib/v/checker/tests/par_expr_decl_assign_err.vv

diff --git a/vlib/v/checker/assign.v b/vlib/v/checker/assign.v
index 724ce57aa..28b3241ec 100644
--- a/vlib/v/checker/assign.v
+++ b/vlib/v/checker/assign.v
@@ -267,6 +267,11 @@ fn (mut c Checker) assign_stmt(mut node ast.AssignStmt) {
 			}
 		}
 		node.left_types << left_type
+
+		if left is ast.ParExpr && is_decl {
+			c.error('parentheses are not supported on the left side of `:=`', left.pos())
+		}
+
 		for left is ast.ParExpr {
 			left = (left as ast.ParExpr).expr
 		}
diff --git a/vlib/v/checker/tests/par_expr_decl_assign_err.out b/vlib/v/checker/tests/par_expr_decl_assign_err.out
new file mode 100644
index 000000000..d77ba2cd3
--- /dev/null
+++ b/vlib/v/checker/tests/par_expr_decl_assign_err.out
@@ -0,0 +1,5 @@
+vlib/v/checker/tests/par_expr_decl_assign_err.vv:2:2: error: parentheses are not supported on the left side of `:=`
+    1 | fn main() {
+    2 |     (x) := 5
+      |     ~~~
+    3 | }
diff --git a/vlib/v/checker/tests/par_expr_decl_assign_err.vv b/vlib/v/checker/tests/par_expr_decl_assign_err.vv
new file mode 100644
index 000000000..c122faa14
--- /dev/null
+++ b/vlib/v/checker/tests/par_expr_decl_assign_err.vv
@@ -0,0 +1,3 @@
+fn main() {
+	(x) := 5
+}
diff --git a/vlib/v/checker/tests/prefix_expr_decl_assign_err.out b/vlib/v/checker/tests/prefix_expr_decl_assign_err.out
index 1842eb032..17eab3890 100644
--- a/vlib/v/checker/tests/prefix_expr_decl_assign_err.out
+++ b/vlib/v/checker/tests/prefix_expr_decl_assign_err.out
@@ -10,6 +10,12 @@ vlib/v/checker/tests/prefix_expr_decl_assign_err.vv:2:5: error: non-name on the
       |     ^
     3 |     (*d) := 14
     4 | }
+vlib/v/checker/tests/prefix_expr_decl_assign_err.vv:3:5: error: parentheses are not supported on the left side of `:=`
+    1 | fn main() {
+    2 |     &a := 12
+    3 |     (*d) := 14
+      |     ~~~~
+    4 | }
 vlib/v/checker/tests/prefix_expr_decl_assign_err.vv:3:10: error: modifying variables via dereferencing can only be done in `unsafe` blocks
     1 | fn main() {
     2 |     &a := 12
-- 
2.39.5