From b6ce7cc198a8fb7234fd12d54e98162a90d2e856 Mon Sep 17 00:00:00 2001
From: yuyi <yuyi98@163.com>
Date: Sat, 30 Jul 2022 19:27:28 +0800
Subject: [PATCH] checker: check invalid variable (fix #15240) (#15260)

---
 vlib/v/checker/checker.v                      |  3 +++
 vlib/v/checker/tests/invalid_variable_err.out | 19 +++++++++++++++++++
 vlib/v/checker/tests/invalid_variable_err.vv  |  5 +++++
 3 files changed, 27 insertions(+)
 create mode 100644 vlib/v/checker/tests/invalid_variable_err.out
 create mode 100644 vlib/v/checker/tests/invalid_variable_err.vv

diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index 7c9ceb6b90..521d77ba46 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -2756,6 +2756,9 @@ pub fn (mut c Checker) ident(mut node ast.Ident) ast.Type {
 							} else {
 								typ = obj.expr.expr_type.clear_flag(.optional).clear_flag(.result)
 							}
+						} else if obj.expr is ast.EmptyExpr {
+							c.error('invalid variable `$node.name`', node.pos)
+							typ = ast.void_type
 						} else {
 							typ = c.expr(obj.expr)
 						}
diff --git a/vlib/v/checker/tests/invalid_variable_err.out b/vlib/v/checker/tests/invalid_variable_err.out
new file mode 100644
index 0000000000..42aa07c6ef
--- /dev/null
+++ b/vlib/v/checker/tests/invalid_variable_err.out
@@ -0,0 +1,19 @@
+vlib/v/checker/tests/invalid_variable_err.vv:2:5: warning: unused variable: `b`
+    1 | fn main() {
+    2 |     a, b := c
+      |        ^
+    3 |     if a {
+    4 |     }
+vlib/v/checker/tests/invalid_variable_err.vv:2:7: error: assignment mismatch: 2 variable(s) 1 value(s)
+    1 | fn main() {
+    2 |     a, b := c
+      |          ~~
+    3 |     if a {
+    4 |     }
+vlib/v/checker/tests/invalid_variable_err.vv:3:5: error: invalid variable `a`
+    1 | fn main() {
+    2 |     a, b := c
+    3 |     if a {
+      |        ^
+    4 |     }
+    5 | }
diff --git a/vlib/v/checker/tests/invalid_variable_err.vv b/vlib/v/checker/tests/invalid_variable_err.vv
new file mode 100644
index 0000000000..f324336f94
--- /dev/null
+++ b/vlib/v/checker/tests/invalid_variable_err.vv
@@ -0,0 +1,5 @@
+fn main() {
+	a, b := c
+	if a {
+	}
+}