From 8ae23cd89efdd443371cf74beb6a39217c74d04d Mon Sep 17 00:00:00 2001
From: zakuro <z@kuro.red>
Date: Mon, 8 Feb 2021 23:55:01 +0900
Subject: [PATCH] parser: make `v := f(v)' an undefined variable error (#8634)

---
 vlib/v/checker/tests/assign_expr_undefined_err_h.out | 7 +++++++
 vlib/v/checker/tests/assign_expr_undefined_err_h.vv  | 8 ++++++++
 vlib/v/parser/assign.v                               | 3 +++
 3 files changed, 18 insertions(+)
 create mode 100644 vlib/v/checker/tests/assign_expr_undefined_err_h.out
 create mode 100644 vlib/v/checker/tests/assign_expr_undefined_err_h.vv

diff --git a/vlib/v/checker/tests/assign_expr_undefined_err_h.out b/vlib/v/checker/tests/assign_expr_undefined_err_h.out
new file mode 100644
index 0000000000..9c647c86b5
--- /dev/null
+++ b/vlib/v/checker/tests/assign_expr_undefined_err_h.out
@@ -0,0 +1,7 @@
+vlib/v/checker/tests/assign_expr_undefined_err_h.vv:6:9: error: undefined variable: `n`
+    4 | 
+    5 | fn main() {
+    6 |     n := f(n)
+      |            ^
+    7 |     println(n)
+    8 | }
diff --git a/vlib/v/checker/tests/assign_expr_undefined_err_h.vv b/vlib/v/checker/tests/assign_expr_undefined_err_h.vv
new file mode 100644
index 0000000000..d872d7eb87
--- /dev/null
+++ b/vlib/v/checker/tests/assign_expr_undefined_err_h.vv
@@ -0,0 +1,8 @@
+fn f(i int) int {
+	return i
+}
+
+fn main() {
+	n := f(n)
+	println(n)
+}
diff --git a/vlib/v/parser/assign.v b/vlib/v/parser/assign.v
index 69cd4ae837..2f1acb0148 100644
--- a/vlib/v/parser/assign.v
+++ b/vlib/v/parser/assign.v
@@ -25,6 +25,9 @@ fn (mut p Parser) check_undefined_variables(exprs []ast.Expr, val ast.Expr) ? {
 		}
 		ast.CallExpr {
 			p.check_undefined_variables(exprs, val.left) ?
+			for arg in val.args {
+				p.check_undefined_variables(exprs, arg.expr) ?
+			}
 		}
 		ast.InfixExpr {
 			p.check_undefined_variables(exprs, val.left) ?