From 8fe70a24a86f197fce595aa8d7ad86f43b57eef5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Uwe=20Kr=C3=BCger?=
 <45282134+UweKrueger@users.noreply.github.com>
Date: Fri, 26 Jun 2020 23:31:38 +0200
Subject: [PATCH] checker: forbid non-reference mut arg or receiver of go
 function

---
 vlib/v/checker/checker.v                 | 13 +++++++++++++
 vlib/v/checker/tests/go_mut_arg.out      |  6 ++++++
 vlib/v/checker/tests/go_mut_arg.vv       | 15 +++++++++++++++
 vlib/v/checker/tests/go_mut_receiver.out |  6 ++++++
 vlib/v/checker/tests/go_mut_receiver.vv  | 15 +++++++++++++++
 5 files changed, 55 insertions(+)
 create mode 100644 vlib/v/checker/tests/go_mut_arg.out
 create mode 100644 vlib/v/checker/tests/go_mut_arg.vv
 create mode 100644 vlib/v/checker/tests/go_mut_receiver.out
 create mode 100644 vlib/v/checker/tests/go_mut_receiver.vv

diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index 7f41800367..103beb43c8 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -1826,6 +1826,19 @@ fn (mut c Checker) stmt(node ast.Stmt) {
 				c.error('expression in `go` must be a function call', it.call_expr.position())
 			}
 			c.expr(it.call_expr)
+			if it.call_expr is ast.CallExpr {
+				call_expr := it.call_expr as ast.CallExpr
+
+				// Make sure there are no mutable arguments
+				for arg in call_expr.args {
+					if arg.is_mut && !arg.typ.is_ptr() {
+						c.error('function in `go` statement cannot contain mutable non-reference arguments', arg.expr.position())
+					}
+				}
+				if call_expr.is_method && call_expr.receiver_type.is_ptr() && !call_expr.left_type.is_ptr() {
+					c.error('method in `go` statement cannot have non-reference mutable receiver', call_expr.left.position())
+				}
+			}
 		}
 		// ast.HashStmt {}
 		ast.Import {}
diff --git a/vlib/v/checker/tests/go_mut_arg.out b/vlib/v/checker/tests/go_mut_arg.out
new file mode 100644
index 0000000000..3544f2cd87
--- /dev/null
+++ b/vlib/v/checker/tests/go_mut_arg.out
@@ -0,0 +1,6 @@
+vlib/v/checker/tests/go_mut_arg.v:14:16: error: function in `go` statement cannot contain mutable non-reference arguments 
+   12 |         a: 0
+   13 |     }
+   14 |     go change(mut x)
+      |                   ^
+   15 | }
diff --git a/vlib/v/checker/tests/go_mut_arg.vv b/vlib/v/checker/tests/go_mut_arg.vv
new file mode 100644
index 0000000000..af86f15d1c
--- /dev/null
+++ b/vlib/v/checker/tests/go_mut_arg.vv
@@ -0,0 +1,15 @@
+struct St {
+mut:
+	a int
+}
+
+fn change(mut a St) {
+	a.a++
+}
+
+fn main() {
+	mut x := St{
+		a: 0
+	}
+	go change(mut x)
+}
diff --git a/vlib/v/checker/tests/go_mut_receiver.out b/vlib/v/checker/tests/go_mut_receiver.out
new file mode 100644
index 0000000000..5033b5d2be
--- /dev/null
+++ b/vlib/v/checker/tests/go_mut_receiver.out
@@ -0,0 +1,6 @@
+vlib/v/checker/tests/go_mut_receiver.v:14:5: error: method in `go` statement cannot have non-reference mutable receiver 
+   12 |         a: 0
+   13 |     }
+   14 |     go x.change()
+      |        ^
+   15 | }
diff --git a/vlib/v/checker/tests/go_mut_receiver.vv b/vlib/v/checker/tests/go_mut_receiver.vv
new file mode 100644
index 0000000000..0b64d51c23
--- /dev/null
+++ b/vlib/v/checker/tests/go_mut_receiver.vv
@@ -0,0 +1,15 @@
+struct St {
+mut:
+	a int
+}
+
+fn (mut a St) change() {
+	a.a++
+}
+
+fn main() {
+	mut x := St{
+		a: 0
+	}
+	go x.change()
+}