Add 'negative' test for 2015 exception

Author: benschulz

tests/ui/lint/unused/unused-parens-trait-obj-e2015.rs

@@ -0,0 +1,15 @@
+//@ check-pass
+//@ edition: 2015
+
+#![deny(unused_parens)]
+
+mod dyn {
+    pub type IsAContextualKeywordIn2015 = ();
+}
+
+pub type DynIsAContextualKeywordIn2015A = dyn::IsAContextualKeywordIn2015;
+
+// there's no lint here, because the type of how dyn is parsed in edition 2015
+pub type DynIsAContextualKeywordIn2015B = Box<dyn (::std::ops::Fn())>;
+
+fn main() {}

tests/ui/lint/unused/unused-parens-trait-obj-e2018-and-after.fixed

@@ -0,0 +1,8 @@
+//@ run-rustfix
+//@ edition: 2018
+
+#![deny(unused_parens)]
+
+pub type DynIsAContextualKeywordIn2015 = Box<dyn ::std::ops::Fn()>; //~ ERROR unnecessary parentheses around type
+
+fn main() {}

tests/ui/lint/unused/unused-parens-trait-obj-e2018-and-after.rs

@@ -0,0 +1,8 @@
+//@ run-rustfix
+//@ edition: 2018
+
+#![deny(unused_parens)]
+
+pub type DynIsAContextualKeywordIn2015 = Box<dyn (::std::ops::Fn())>; //~ ERROR unnecessary parentheses around type
+
+fn main() {}

tests/ui/lint/unused/unused-parens-trait-obj.e2018.stderr renamed to tests/ui/lint/unused/unused-parens-trait-obj-e2018-and-after.stderr

@@ -1,11 +1,11 @@
 error: unnecessary parentheses around type
-  --> $DIR/unused-parens-trait-obj.rs:9:50
+  --> $DIR/unused-parens-trait-obj-e2018-and-after.rs:6:50
    |
 LL | pub type DynIsAContextualKeywordIn2015 = Box<dyn (::std::ops::Fn())>;
    |                                                  ^                ^
    |
 note: the lint level is defined here
-  --> $DIR/unused-parens-trait-obj.rs:7:9
+  --> $DIR/unused-parens-trait-obj-e2018-and-after.rs:4:9
    |
 LL | #![deny(unused_parens)]
    |         ^^^^^^^^^^^^^