From 861bbe68f20fa81805d4fa0cbd2756411f438a89 Mon Sep 17 00:00:00 2001
From: Swastik Baranwal <swstkbaranwal@gmail.com>
Date: Fri, 27 Sep 2024 04:55:17 +0530
Subject: [PATCH] checker: disallow infix exper on left side of assign 
 (#22322)

---
 vlib/v/checker/assign.v                             |  4 ++++
 .../tests/infix_expr_left_side_assogn_err.out       | 13 +++++++++++++
 .../tests/infix_expr_left_side_assogn_err.vv        |  6 ++++++
 vlib/v/checker/tests/invalid_literal_assign_err.out | 13 +++++++++++++
 4 files changed, 36 insertions(+)
 create mode 100644 vlib/v/checker/tests/infix_expr_left_side_assogn_err.out
 create mode 100644 vlib/v/checker/tests/infix_expr_left_side_assogn_err.vv

diff --git a/vlib/v/checker/assign.v b/vlib/v/checker/assign.v
index 0d4c90984..ebccbfb73 100644
--- a/vlib/v/checker/assign.v
+++ b/vlib/v/checker/assign.v
@@ -495,6 +495,10 @@ fn (mut c Checker) assign_stmt(mut node ast.AssignStmt) {
 						left.recursive_mapset_is_setter(true)
 					}
 				}
+				if mut left is ast.InfixExpr {
+					c.error('cannot use infix expression on the left side of `${node.op}`',
+						left.pos)
+				}
 				if is_decl {
 					c.error('non-name `${left}` on left side of `:=`', left.pos())
 				}
diff --git a/vlib/v/checker/tests/infix_expr_left_side_assogn_err.out b/vlib/v/checker/tests/infix_expr_left_side_assogn_err.out
new file mode 100644
index 000000000..a7ca5f093
--- /dev/null
+++ b/vlib/v/checker/tests/infix_expr_left_side_assogn_err.out
@@ -0,0 +1,13 @@
+vlib/v/checker/tests/infix_expr_left_side_assogn_err.vv:4:4: error: cannot use infix expression on the left side of `=`
+    2 |     a := 69
+    3 |     b := 420
+    4 |     a + b = a + b
+      |       ^
+    5 |     (a + b) = a + b
+    6 | }
+vlib/v/checker/tests/infix_expr_left_side_assogn_err.vv:5:5: error: cannot use infix expression on the left side of `=`
+    3 |     b := 420
+    4 |     a + b = a + b
+    5 |     (a + b) = a + b
+      |        ^
+    6 | }
diff --git a/vlib/v/checker/tests/infix_expr_left_side_assogn_err.vv b/vlib/v/checker/tests/infix_expr_left_side_assogn_err.vv
new file mode 100644
index 000000000..92ba4615d
--- /dev/null
+++ b/vlib/v/checker/tests/infix_expr_left_side_assogn_err.vv
@@ -0,0 +1,6 @@
+fn main() {
+	a := 69
+	b := 420
+	a + b = a + b
+	(a + b) = a + b
+}
diff --git a/vlib/v/checker/tests/invalid_literal_assign_err.out b/vlib/v/checker/tests/invalid_literal_assign_err.out
index 1c87f47c6..2131ce5cc 100644
--- a/vlib/v/checker/tests/invalid_literal_assign_err.out
+++ b/vlib/v/checker/tests/invalid_literal_assign_err.out
@@ -47,6 +47,13 @@ vlib/v/checker/tests/invalid_literal_assign_err.vv:10:2: error: non-name literal
       |     ~~~~
    11 |     3 + 5 = 3 & 4
    12 |     (3 + 3.5) = 4 + 6.4
+vlib/v/checker/tests/invalid_literal_assign_err.vv:11:4: error: cannot use infix expression on the left side of `=`
+    9 |     Foo{} = Foo{}
+   10 |     true = false
+   11 |     3 + 5 = 3 & 4
+      |       ^
+   12 |     (3 + 3.5) = 4 + 6.4
+   13 | }
 vlib/v/checker/tests/invalid_literal_assign_err.vv:11:2: error: non-name literal value `3 + 5` on left side of `=`
     9 |     Foo{} = Foo{}
    10 |     true = false
@@ -54,6 +61,12 @@ vlib/v/checker/tests/invalid_literal_assign_err.vv:11:2: error: non-name literal
       |     ~~~~~
    12 |     (3 + 3.5) = 4 + 6.4
    13 | }
+vlib/v/checker/tests/invalid_literal_assign_err.vv:12:5: error: cannot use infix expression on the left side of `=`
+   10 |     true = false
+   11 |     3 + 5 = 3 & 4
+   12 |     (3 + 3.5) = 4 + 6.4
+      |        ^
+   13 | }
 vlib/v/checker/tests/invalid_literal_assign_err.vv:12:3: error: non-name literal value `3 + 3.5` on left side of `=`
    10 |     true = false
    11 |     3 + 5 = 3 & 4
-- 
2.39.5