Add some more rustc test cases

Author: killercup

tests/fixtures/closure-immutable-outer-variable.fixed.rs

@@ -0,0 +1,20 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Point at the captured immutable outer variable
+
+fn foo(mut f: Box<FnMut()>) {
+    f();
+}
+
+fn main() {
+    let mut y = true;
+    foo(Box::new(move || y = false) as Box<_>); //~ ERROR cannot assign to captured outer variable
+}

tests/fixtures/closure-immutable-outer-variable.json

@@ -0,0 +1 @@
+{"message":"cannot assign to captured outer variable in an `FnMut` closure","code":{"code":"E0594","explanation":null},"level":"error","spans":[{"file_name":"./tests/fixtures/closure-immutable-outer-variable.rs","byte_start":615,"byte_end":624,"line_start":19,"line_end":19,"column_start":26,"column_end":35,"is_primary":true,"text":[{"text":"    foo(Box::new(move || y = false) as Box<_>); //~ ERROR cannot assign to captured outer variable","highlight_start":26,"highlight_end":35}],"label":null,"suggested_replacement":null,"expansion":null}],"children":[{"message":"consider making `y` mutable","code":null,"level":"help","spans":[{"file_name":"./tests/fixtures/closure-immutable-outer-variable.rs","byte_start":580,"byte_end":581,"line_start":18,"line_end":18,"column_start":9,"column_end":10,"is_primary":true,"text":[{"text":"    let y = true;","highlight_start":9,"highlight_end":10}],"label":null,"suggested_replacement":"mut y","expansion":null}],"children":[],"rendered":null}],"rendered":"error[E0594]: cannot assign to captured outer variable in an `FnMut` closure\n  --> ./tests/fixtures/closure-immutable-outer-variable.rs:19:26\n   |\n18 |     let y = true;\n   |         - help: consider making `y` mutable: `mut y`\n19 |     foo(Box::new(move || y = false) as Box<_>); //~ ERROR cannot assign to captured outer variable\n   |                          ^^^^^^^^^\n\n"}

tests/fixtures/closure-immutable-outer-variable.rs

@@ -0,0 +1,20 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Point at the captured immutable outer variable
+
+fn foo(mut f: Box<FnMut()>) {
+    f();
+}
+
+fn main() {
+    let y = true;
+    foo(Box::new(move || y = false) as Box<_>); //~ ERROR cannot assign to captured outer variable
+}