Detect more cases of unused_parens around types

11 files changed, 422 insertions, 55 deletions

diff --git a/tests/ui/lint/lint-unnecessary-parens.fixed b/tests/ui/lint/lint-unnecessary-parens.fixed
index a8c8dd1d512..be322a31363 100644
--- a/tests/ui/lint/lint-unnecessary-parens.fixed
+++ b/tests/ui/lint/lint-unnecessary-parens.fixed
@@ -1,5 +1,6 @@
 //@ run-rustfix
 
+#![feature(impl_trait_in_fn_trait_return)]
 #![deny(unused_parens)]
 #![allow(while_true)] // for rustfix
 
@@ -16,11 +17,11 @@ fn bar(y: bool) -> X {
     return X { y }; //~ ERROR unnecessary parentheses around `return` value
 }
 
-pub fn unused_parens_around_return_type() -> u32 { //~ ERROR unnecessary parentheses around type
+pub fn around_return_type() -> u32 { //~ ERROR unnecessary parentheses around type
     panic!()
 }
 
-pub fn unused_parens_around_block_return() -> u32 {
+pub fn around_block_return() -> u32 {
     let _foo = {
         5 //~ ERROR unnecessary parentheses around block return value
     };
@@ -31,10 +32,90 @@ pub trait Trait {
     fn test(&self);
 }
 
-pub fn passes_unused_parens_lint() -> &'static (dyn Trait) {
+pub fn around_multi_bound_ref() -> &'static (dyn Trait + Send) {
     panic!()
 }
 
+//~v ERROR unnecessary parentheses around type
+pub fn around_single_bound_ref() -> &'static dyn Trait {
+    panic!()
+}
+
+pub fn around_multi_bound_ptr() -> *const (dyn Trait + Send) {
+    panic!()
+}
+
+//~v ERROR unnecessary parentheses around type
+pub fn around_single_bound_ptr() -> *const dyn Trait {
+    panic!()
+}
+
+pub fn around_multi_bound_dyn_fn_output() -> &'static dyn FnOnce() -> (impl Send + Sync) {
+    &|| ()
+}
+
+//~v ERROR unnecessary parentheses around type
+pub fn around_single_bound_dyn_fn_output() -> &'static dyn FnOnce() -> impl Send {
+    &|| ()
+}
+
+pub fn around_dyn_fn_output_given_more_bounds() -> &'static (dyn FnOnce() -> (impl Send) + Sync) {
+    &|| ()
+}
+
+pub fn around_multi_bound_impl_fn_output() -> impl FnOnce() -> (impl Send + Sync) {
+    || ()
+}
+
+//~v ERROR unnecessary parentheses around type
+pub fn around_single_bound_impl_fn_output() -> impl FnOnce() -> impl Send {
+    || ()
+}
+
+pub fn around_impl_fn_output_given_more_bounds() -> impl FnOnce() -> (impl Send) + Sync {
+    || ()
+}
+
+//~v ERROR unnecessary parentheses around type
+pub fn around_dyn_bound() -> &'static dyn FnOnce() {
+    &|| ()
+}
+
+//~v ERROR unnecessary parentheses around type
+pub fn around_impl_trait_bound() -> impl FnOnce() {
+    || ()
+}
+
+// these parens aren't strictly required but they help disambiguate => no lint
+pub fn around_fn_bound_with_explicit_ret_ty() -> impl (Fn() -> ()) + Send {
+    || ()
+}
+
+//~v ERROR unnecessary parentheses around type
+pub fn around_fn_bound_with_implicit_ret_ty() -> impl Fn() + Send {
+    || ()
+}
+
+//~v ERROR unnecessary parentheses around type
+pub fn around_last_fn_bound_with_explicit_ret_ty() -> impl Send + Fn() -> () {
+    || ()
+}
+
+//~v ERROR unnecessary parentheses around type
+pub fn around_regular_bound1() -> &'static (dyn Send + Sync) {
+    &|| ()
+}
+
+//~v ERROR unnecessary parentheses around type
+pub fn around_regular_bound2() -> &'static (dyn Send + Sync) {
+    &|| ()
+}
+
+//~v ERROR unnecessary parentheses around type
+pub fn around_regular_bound3() -> &'static (dyn Send + ::std::marker::Sync) {
+    &|| ()
+}
+
 pub fn parens_with_keyword(e: &[()]) -> i32 {
     if true {} //~ ERROR unnecessary parentheses around `if`
     while true {} //~ ERROR unnecessary parentheses around `while`
diff --git a/tests/ui/lint/lint-unnecessary-parens.rs b/tests/ui/lint/lint-unnecessary-parens.rs
index 02aa78283c7..dccad07311b 100644
--- a/tests/ui/lint/lint-unnecessary-parens.rs
+++ b/tests/ui/lint/lint-unnecessary-parens.rs
@@ -1,5 +1,6 @@
 //@ run-rustfix
 
+#![feature(impl_trait_in_fn_trait_return)]
 #![deny(unused_parens)]
 #![allow(while_true)] // for rustfix
 
@@ -16,11 +17,11 @@ fn bar(y: bool) -> X {
     return (X { y }); //~ ERROR unnecessary parentheses around `return` value
 }
 
-pub fn unused_parens_around_return_type() -> (u32) { //~ ERROR unnecessary parentheses around type
+pub fn around_return_type() -> (u32) { //~ ERROR unnecessary parentheses around type
     panic!()
 }
 
-pub fn unused_parens_around_block_return() -> u32 {
+pub fn around_block_return() -> u32 {
     let _foo = {
         (5) //~ ERROR unnecessary parentheses around block return value
     };
@@ -31,10 +32,90 @@ pub trait Trait {
     fn test(&self);
 }
 
-pub fn passes_unused_parens_lint() -> &'static (dyn Trait) {
+pub fn around_multi_bound_ref() -> &'static (dyn Trait + Send) {
     panic!()
 }
 
+//~v ERROR unnecessary parentheses around type
+pub fn around_single_bound_ref() -> &'static (dyn Trait) {
+    panic!()
+}
+
+pub fn around_multi_bound_ptr() -> *const (dyn Trait + Send) {
+    panic!()
+}
+
+//~v ERROR unnecessary parentheses around type
+pub fn around_single_bound_ptr() -> *const (dyn Trait) {
+    panic!()
+}
+
+pub fn around_multi_bound_dyn_fn_output() -> &'static dyn FnOnce() -> (impl Send + Sync) {
+    &|| ()
+}
+
+//~v ERROR unnecessary parentheses around type
+pub fn around_single_bound_dyn_fn_output() -> &'static dyn FnOnce() -> (impl Send) {
+    &|| ()
+}
+
+pub fn around_dyn_fn_output_given_more_bounds() -> &'static (dyn FnOnce() -> (impl Send) + Sync) {
+    &|| ()
+}
+
+pub fn around_multi_bound_impl_fn_output() -> impl FnOnce() -> (impl Send + Sync) {
+    || ()
+}
+
+//~v ERROR unnecessary parentheses around type
+pub fn around_single_bound_impl_fn_output() -> impl FnOnce() -> (impl Send) {
+    || ()
+}
+
+pub fn around_impl_fn_output_given_more_bounds() -> impl FnOnce() -> (impl Send) + Sync {
+    || ()
+}
+
+//~v ERROR unnecessary parentheses around type
+pub fn around_dyn_bound() -> &'static dyn (FnOnce()) {
+    &|| ()
+}
+
+//~v ERROR unnecessary parentheses around type
+pub fn around_impl_trait_bound() -> impl (FnOnce()) {
+    || ()
+}
+
+// these parens aren't strictly required but they help disambiguate => no lint
+pub fn around_fn_bound_with_explicit_ret_ty() -> impl (Fn() -> ()) + Send {
+    || ()
+}
+
+//~v ERROR unnecessary parentheses around type
+pub fn around_fn_bound_with_implicit_ret_ty() -> impl (Fn()) + Send {
+    || ()
+}
+
+//~v ERROR unnecessary parentheses around type
+pub fn around_last_fn_bound_with_explicit_ret_ty() -> impl Send + (Fn() -> ()) {
+    || ()
+}
+
+//~v ERROR unnecessary parentheses around type
+pub fn around_regular_bound1() -> &'static (dyn (Send) + Sync) {
+    &|| ()
+}
+
+//~v ERROR unnecessary parentheses around type
+pub fn around_regular_bound2() -> &'static (dyn Send + (Sync)) {
+    &|| ()
+}
+
+//~v ERROR unnecessary parentheses around type
+pub fn around_regular_bound3() -> &'static (dyn Send + (::std::marker::Sync)) {
+    &|| ()
+}
+
 pub fn parens_with_keyword(e: &[()]) -> i32 {
     if(true) {} //~ ERROR unnecessary parentheses around `if`
     while(true) {} //~ ERROR unnecessary parentheses around `while`
diff --git a/tests/ui/lint/lint-unnecessary-parens.stderr b/tests/ui/lint/lint-unnecessary-parens.stderr
index f2e5debd6e0..a7fc1e89c6c 100644
--- a/tests/ui/lint/lint-unnecessary-parens.stderr
+++ b/tests/ui/lint/lint-unnecessary-parens.stderr
@@ -1,11 +1,11 @@
 error: unnecessary parentheses around `return` value
-  --> $DIR/lint-unnecessary-parens.rs:13:12
+  --> $DIR/lint-unnecessary-parens.rs:14:12
    |
 LL |     return (1);
    |            ^ ^
    |
 note: the lint level is defined here
-  --> $DIR/lint-unnecessary-parens.rs:3:9
+  --> $DIR/lint-unnecessary-parens.rs:4:9
    |
 LL | #![deny(unused_parens)]
    |         ^^^^^^^^^^^^^
@@ -16,7 +16,7 @@ LL +     return 1;
    |
 
 error: unnecessary parentheses around `return` value
-  --> $DIR/lint-unnecessary-parens.rs:16:12
+  --> $DIR/lint-unnecessary-parens.rs:17:12
    |
 LL |     return (X { y });
    |            ^       ^
@@ -28,19 +28,19 @@ LL +     return X { y };
    |
 
 error: unnecessary parentheses around type
-  --> $DIR/lint-unnecessary-parens.rs:19:46
+  --> $DIR/lint-unnecessary-parens.rs:20:32
    |
-LL | pub fn unused_parens_around_return_type() -> (u32) {
-   |                                              ^   ^
+LL | pub fn around_return_type() -> (u32) {
+   |                                ^   ^
    |
 help: remove these parentheses
    |
-LL - pub fn unused_parens_around_return_type() -> (u32) {
-LL + pub fn unused_parens_around_return_type() -> u32 {
+LL - pub fn around_return_type() -> (u32) {
+LL + pub fn around_return_type() -> u32 {
    |
 
 error: unnecessary parentheses around block return value
-  --> $DIR/lint-unnecessary-parens.rs:25:9
+  --> $DIR/lint-unnecessary-parens.rs:26:9
    |
 LL |         (5)
    |         ^ ^
@@ -52,7 +52,7 @@ LL +         5
    |
 
 error: unnecessary parentheses around block return value
-  --> $DIR/lint-unnecessary-parens.rs:27:5
+  --> $DIR/lint-unnecessary-parens.rs:28:5
    |
 LL |     (5)
    |     ^ ^
@@ -63,8 +63,140 @@ LL -     (5)
 LL +     5
    |
 
+error: unnecessary parentheses around type
+  --> $DIR/lint-unnecessary-parens.rs:40:46
+   |
+LL | pub fn around_single_bound_ref() -> &'static (dyn Trait) {
+   |                                              ^         ^
+   |
+help: remove these parentheses
+   |
+LL - pub fn around_single_bound_ref() -> &'static (dyn Trait) {
+LL + pub fn around_single_bound_ref() -> &'static dyn Trait {
+   |
+
+error: unnecessary parentheses around type
+  --> $DIR/lint-unnecessary-parens.rs:49:44
+   |
+LL | pub fn around_single_bound_ptr() -> *const (dyn Trait) {
+   |                                            ^         ^
+   |
+help: remove these parentheses
+   |
+LL - pub fn around_single_bound_ptr() -> *const (dyn Trait) {
+LL + pub fn around_single_bound_ptr() -> *const dyn Trait {
+   |
+
+error: unnecessary parentheses around type
+  --> $DIR/lint-unnecessary-parens.rs:58:72
+   |
+LL | pub fn around_single_bound_dyn_fn_output() -> &'static dyn FnOnce() -> (impl Send) {
+   |                                                                        ^         ^
+   |
+help: remove these parentheses
+   |
+LL - pub fn around_single_bound_dyn_fn_output() -> &'static dyn FnOnce() -> (impl Send) {
+LL + pub fn around_single_bound_dyn_fn_output() -> &'static dyn FnOnce() -> impl Send {
+   |
+
+error: unnecessary parentheses around type
+  --> $DIR/lint-unnecessary-parens.rs:71:65
+   |
+LL | pub fn around_single_bound_impl_fn_output() -> impl FnOnce() -> (impl Send) {
+   |                                                                 ^         ^
+   |
+help: remove these parentheses
+   |
+LL - pub fn around_single_bound_impl_fn_output() -> impl FnOnce() -> (impl Send) {
+LL + pub fn around_single_bound_impl_fn_output() -> impl FnOnce() -> impl Send {
+   |
+
+error: unnecessary parentheses around type
+  --> $DIR/lint-unnecessary-parens.rs:80:43
+   |
+LL | pub fn around_dyn_bound() -> &'static dyn (FnOnce()) {
+   |                                           ^        ^
+   |
+help: remove these parentheses
+   |
+LL - pub fn around_dyn_bound() -> &'static dyn (FnOnce()) {
+LL + pub fn around_dyn_bound() -> &'static dyn FnOnce() {
+   |
+
+error: unnecessary parentheses around type
+  --> $DIR/lint-unnecessary-parens.rs:85:42
+   |
+LL | pub fn around_impl_trait_bound() -> impl (FnOnce()) {
+   |                                          ^        ^
+   |
+help: remove these parentheses
+   |
+LL - pub fn around_impl_trait_bound() -> impl (FnOnce()) {
+LL + pub fn around_impl_trait_bound() -> impl FnOnce() {
+   |
+
+error: unnecessary parentheses around type
+  --> $DIR/lint-unnecessary-parens.rs:95:55
+   |
+LL | pub fn around_fn_bound_with_implicit_ret_ty() -> impl (Fn()) + Send {
+   |                                                       ^    ^
+   |
+help: remove these parentheses
+   |
+LL - pub fn around_fn_bound_with_implicit_ret_ty() -> impl (Fn()) + Send {
+LL + pub fn around_fn_bound_with_implicit_ret_ty() -> impl Fn() + Send {
+   |
+
+error: unnecessary parentheses around type
+  --> $DIR/lint-unnecessary-parens.rs:100:67
+   |
+LL | pub fn around_last_fn_bound_with_explicit_ret_ty() -> impl Send + (Fn() -> ()) {
+   |                                                                   ^          ^
+   |
+help: remove these parentheses
+   |
+LL - pub fn around_last_fn_bound_with_explicit_ret_ty() -> impl Send + (Fn() -> ()) {
+LL + pub fn around_last_fn_bound_with_explicit_ret_ty() -> impl Send + Fn() -> () {
+   |
+
+error: unnecessary parentheses around type
+  --> $DIR/lint-unnecessary-parens.rs:105:49
+   |
+LL | pub fn around_regular_bound1() -> &'static (dyn (Send) + Sync) {
+   |                                                 ^    ^
+   |
+help: remove these parentheses
+   |
+LL - pub fn around_regular_bound1() -> &'static (dyn (Send) + Sync) {
+LL + pub fn around_regular_bound1() -> &'static (dyn Send + Sync) {
+   |
+
+error: unnecessary parentheses around type
+  --> $DIR/lint-unnecessary-parens.rs:110:56
+   |
+LL | pub fn around_regular_bound2() -> &'static (dyn Send + (Sync)) {
+   |                                                        ^    ^
+   |
+help: remove these parentheses
+   |
+LL - pub fn around_regular_bound2() -> &'static (dyn Send + (Sync)) {
+LL + pub fn around_regular_bound2() -> &'static (dyn Send + Sync) {
+   |
+
+error: unnecessary parentheses around type
+  --> $DIR/lint-unnecessary-parens.rs:115:56
+   |
+LL | pub fn around_regular_bound3() -> &'static (dyn Send + (::std::marker::Sync)) {
+   |                                                        ^                   ^
+   |
+help: remove these parentheses
+   |
+LL - pub fn around_regular_bound3() -> &'static (dyn Send + (::std::marker::Sync)) {
+LL + pub fn around_regular_bound3() -> &'static (dyn Send + ::std::marker::Sync) {
+   |
+
 error: unnecessary parentheses around `if` condition
-  --> $DIR/lint-unnecessary-parens.rs:39:7
+  --> $DIR/lint-unnecessary-parens.rs:120:7
    |
 LL |     if(true) {}
    |       ^    ^
@@ -76,7 +208,7 @@ LL +     if true {}
    |
 
 error: unnecessary parentheses around `while` condition
-  --> $DIR/lint-unnecessary-parens.rs:40:10
+  --> $DIR/lint-unnecessary-parens.rs:121:10
    |
 LL |     while(true) {}
    |          ^    ^
@@ -88,7 +220,7 @@ LL +     while true {}
    |
 
 error: unnecessary parentheses around `for` iterator expression
-  --> $DIR/lint-unnecessary-parens.rs:41:13
+  --> $DIR/lint-unnecessary-parens.rs:122:13
    |
 LL |     for _ in(e) {}
    |             ^ ^
@@ -100,7 +232,7 @@ LL +     for _ in e {}
    |
 
 error: unnecessary parentheses around `match` scrutinee expression
-  --> $DIR/lint-unnecessary-parens.rs:42:10
+  --> $DIR/lint-unnecessary-parens.rs:123:10
    |
 LL |     match(1) { _ => ()}
    |          ^ ^
@@ -112,7 +244,7 @@ LL +     match 1 { _ => ()}
    |
 
 error: unnecessary parentheses around `return` value
-  --> $DIR/lint-unnecessary-parens.rs:43:11
+  --> $DIR/lint-unnecessary-parens.rs:124:11
    |
 LL |     return(1);
    |           ^ ^
@@ -124,7 +256,7 @@ LL +     return 1;
    |
 
 error: unnecessary parentheses around assigned value
-  --> $DIR/lint-unnecessary-parens.rs:74:31
+  --> $DIR/lint-unnecessary-parens.rs:155:31
    |
 LL | pub const CONST_ITEM: usize = (10);
    |                               ^  ^
@@ -136,7 +268,7 @@ LL + pub const CONST_ITEM: usize = 10;
    |
 
 error: unnecessary parentheses around assigned value
-  --> $DIR/lint-unnecessary-parens.rs:75:33
+  --> $DIR/lint-unnecessary-parens.rs:156:33
    |
 LL | pub static STATIC_ITEM: usize = (10);
    |                                 ^  ^
@@ -148,7 +280,7 @@ LL + pub static STATIC_ITEM: usize = 10;
    |
 
 error: unnecessary parentheses around function argument
-  --> $DIR/lint-unnecessary-parens.rs:79:9
+  --> $DIR/lint-unnecessary-parens.rs:160:9
    |
 LL |     bar((true));
    |         ^    ^
@@ -160,7 +292,7 @@ LL +     bar(true);
    |
 
 error: unnecessary parentheses around `if` condition
-  --> $DIR/lint-unnecessary-parens.rs:81:8
+  --> $DIR/lint-unnecessary-parens.rs:162:8
    |
 LL |     if (true) {}
    |        ^    ^
@@ -172,7 +304,7 @@ LL +     if true {}
    |
 
 error: unnecessary parentheses around `while` condition
-  --> $DIR/lint-unnecessary-parens.rs:82:11
+  --> $DIR/lint-unnecessary-parens.rs:163:11
    |
 LL |     while (true) {}
    |           ^    ^
@@ -184,7 +316,7 @@ LL +     while true {}
    |
 
 error: unnecessary parentheses around `match` scrutinee expression
-  --> $DIR/lint-unnecessary-parens.rs:83:11
+  --> $DIR/lint-unnecessary-parens.rs:164:11
    |
 LL |     match (true) {
    |           ^    ^
@@ -196,7 +328,7 @@ LL +     match true {
    |
 
 error: unnecessary parentheses around `let` scrutinee expression
-  --> $DIR/lint-unnecessary-parens.rs:86:16
+  --> $DIR/lint-unnecessary-parens.rs:167:16
    |
 LL |     if let 1 = (1) {}
    |                ^ ^
@@ -208,7 +340,7 @@ LL +     if let 1 = 1 {}
    |
 
 error: unnecessary parentheses around `let` scrutinee expression
-  --> $DIR/lint-unnecessary-parens.rs:87:19
+  --> $DIR/lint-unnecessary-parens.rs:168:19
    |
 LL |     while let 1 = (2) {}
    |                   ^ ^
@@ -220,7 +352,7 @@ LL +     while let 1 = 2 {}
    |
 
 error: unnecessary parentheses around method argument
-  --> $DIR/lint-unnecessary-parens.rs:103:24
+  --> $DIR/lint-unnecessary-parens.rs:184:24
    |
 LL |     X { y: false }.foo((true));
    |                        ^    ^
@@ -232,7 +364,7 @@ LL +     X { y: false }.foo(true);
    |
 
 error: unnecessary parentheses around assigned value
-  --> $DIR/lint-unnecessary-parens.rs:105:18
+  --> $DIR/lint-unnecessary-parens.rs:186:18
    |
 LL |     let mut _a = (0);
    |                  ^ ^
@@ -244,7 +376,7 @@ LL +     let mut _a = 0;
    |
 
 error: unnecessary parentheses around assigned value
-  --> $DIR/lint-unnecessary-parens.rs:106:10
+  --> $DIR/lint-unnecessary-parens.rs:187:10
    |
 LL |     _a = (0);
    |          ^ ^
@@ -256,7 +388,7 @@ LL +     _a = 0;
    |
 
 error: unnecessary parentheses around assigned value
-  --> $DIR/lint-unnecessary-parens.rs:107:11
+  --> $DIR/lint-unnecessary-parens.rs:188:11
    |
 LL |     _a += (1);
    |           ^ ^
@@ -268,7 +400,7 @@ LL +     _a += 1;
    |
 
 error: unnecessary parentheses around pattern
-  --> $DIR/lint-unnecessary-parens.rs:109:8
+  --> $DIR/lint-unnecessary-parens.rs:190:8
    |
 LL |     let(mut _a) = 3;
    |        ^      ^
@@ -280,7 +412,7 @@ LL +     let mut _a = 3;
    |
 
 error: unnecessary parentheses around pattern
-  --> $DIR/lint-unnecessary-parens.rs:110:9
+  --> $DIR/lint-unnecessary-parens.rs:191:9
    |
 LL |     let (mut _a) = 3;
    |         ^      ^
@@ -292,7 +424,7 @@ LL +     let mut _a = 3;
    |
 
 error: unnecessary parentheses around pattern
-  --> $DIR/lint-unnecessary-parens.rs:111:8
+  --> $DIR/lint-unnecessary-parens.rs:192:8
    |
 LL |     let( mut _a) = 3;
    |        ^^      ^
@@ -304,7 +436,7 @@ LL +     let mut _a = 3;
    |
 
 error: unnecessary parentheses around pattern
-  --> $DIR/lint-unnecessary-parens.rs:113:8
+  --> $DIR/lint-unnecessary-parens.rs:194:8
    |
 LL |     let(_a) = 3;
    |        ^  ^
@@ -316,7 +448,7 @@ LL +     let _a = 3;
    |
 
 error: unnecessary parentheses around pattern
-  --> $DIR/lint-unnecessary-parens.rs:114:9
+  --> $DIR/lint-unnecessary-parens.rs:195:9
    |
 LL |     let (_a) = 3;
    |         ^  ^
@@ -328,7 +460,7 @@ LL +     let _a = 3;
    |
 
 error: unnecessary parentheses around pattern
-  --> $DIR/lint-unnecessary-parens.rs:115:8
+  --> $DIR/lint-unnecessary-parens.rs:196:8
    |
 LL |     let( _a) = 3;
    |        ^^  ^
@@ -340,7 +472,7 @@ LL +     let _a = 3;
    |
 
 error: unnecessary parentheses around block return value
-  --> $DIR/lint-unnecessary-parens.rs:121:9
+  --> $DIR/lint-unnecessary-parens.rs:202:9
    |
 LL |         (unit!() - One)
    |         ^             ^
@@ -352,7 +484,7 @@ LL +         unit!() - One
    |
 
 error: unnecessary parentheses around block return value
-  --> $DIR/lint-unnecessary-parens.rs:123:9
+  --> $DIR/lint-unnecessary-parens.rs:204:9
    |
 LL |         (unit![] - One)
    |         ^             ^
@@ -364,7 +496,7 @@ LL +         unit![] - One
    |
 
 error: unnecessary parentheses around block return value
-  --> $DIR/lint-unnecessary-parens.rs:126:9
+  --> $DIR/lint-unnecessary-parens.rs:207:9
    |
 LL |         (unit! {} - One)
    |         ^              ^
@@ -376,7 +508,7 @@ LL +         unit! {} - One
    |
 
 error: unnecessary parentheses around assigned value
-  --> $DIR/lint-unnecessary-parens.rs:131:14
+  --> $DIR/lint-unnecessary-parens.rs:212:14
    |
 LL |     let _r = (&x);
    |              ^  ^
@@ -388,7 +520,7 @@ LL +     let _r = &x;
    |
 
 error: unnecessary parentheses around assigned value
-  --> $DIR/lint-unnecessary-parens.rs:132:14
+  --> $DIR/lint-unnecessary-parens.rs:213:14
    |
 LL |     let _r = (&mut x);
    |              ^      ^
@@ -399,5 +531,5 @@ LL -     let _r = (&mut x);
 LL +     let _r = &mut x;
    |
 
-error: aborting due to 33 previous errors
+error: aborting due to 44 previous errors
 
diff --git a/tests/ui/lint/unused/issue-105061-should-lint.rs b/tests/ui/lint/unused/issue-105061-should-lint.rs
index 433c2882089..74a0ff83739 100644
--- a/tests/ui/lint/unused/issue-105061-should-lint.rs
+++ b/tests/ui/lint/unused/issue-105061-should-lint.rs
@@ -14,7 +14,7 @@ where
 trait Hello<T> {}
 fn with_dyn_bound<T>()
 where
-    (dyn Hello<(for<'b> fn(&'b ()))>): Hello<T> //~ ERROR unnecessary parentheses around type
+    dyn Hello<(for<'b> fn(&'b ()))>: Hello<T> //~ ERROR unnecessary parentheses around type
 {}
 
 fn main() {
diff --git a/tests/ui/lint/unused/issue-105061-should-lint.stderr b/tests/ui/lint/unused/issue-105061-should-lint.stderr
index e591f1ffb6b..ae69f018eae 100644
--- a/tests/ui/lint/unused/issue-105061-should-lint.stderr
+++ b/tests/ui/lint/unused/issue-105061-should-lint.stderr
@@ -17,15 +17,15 @@ LL +     for<'b> for<'a> fn(Inv<'a>): Trait<'b>,
    |
 
 error: unnecessary parentheses around type
-  --> $DIR/issue-105061-should-lint.rs:17:16
+  --> $DIR/issue-105061-should-lint.rs:17:15
    |
-LL |     (dyn Hello<(for<'b> fn(&'b ()))>): Hello<T>
-   |                ^                  ^
+LL |     dyn Hello<(for<'b> fn(&'b ()))>: Hello<T>
+   |               ^                  ^
    |
 help: remove these parentheses
    |
-LL -     (dyn Hello<(for<'b> fn(&'b ()))>): Hello<T>
-LL +     (dyn Hello<for<'b> fn(&'b ())>): Hello<T>
+LL -     dyn Hello<(for<'b> fn(&'b ()))>: Hello<T>
+LL +     dyn Hello<for<'b> fn(&'b ())>: Hello<T>
    |
 
 error: aborting due to 2 previous errors
diff --git a/tests/ui/lint/unused/unused-parens-trait-obj.edition2018.fixed b/tests/ui/lint/unused/unused-parens-trait-obj.edition2018.fixed
new file mode 100644
index 00000000000..f95418868e1
--- /dev/null
+++ b/tests/ui/lint/unused/unused-parens-trait-obj.edition2018.fixed
@@ -0,0 +1,27 @@
+//@ revisions: edition2015 edition2018
+//@[edition2015] check-pass
+//@[edition2015] edition: 2015
+//@[edition2018] run-rustfix
+//@[edition2018] edition: 2018
+
+#![deny(unused_parens)]
+
+#[allow(unused)]
+macro_rules! edition2015_only {
+    () => {
+        mod dyn {
+            pub type IsAContextualKeywordIn2015 = ();
+        }
+
+        pub type DynIsAContextualKeywordIn2015A = dyn::IsAContextualKeywordIn2015;
+    }
+}
+
+#[cfg(edition2015)]
+edition2015_only!();
+
+// there's a lint for 2018 and later only because of how dyn is parsed in edition 2015
+//[edition2018]~v ERROR unnecessary parentheses around type
+pub type DynIsAContextualKeywordIn2015B = Box<dyn ::std::ops::Fn()>;
+
+fn main() {}
diff --git a/tests/ui/lint/unused/unused-parens-trait-obj.edition2018.stderr b/tests/ui/lint/unused/unused-parens-trait-obj.edition2018.stderr
new file mode 100644
index 00000000000..aed8cec68e8
--- /dev/null
+++ b/tests/ui/lint/unused/unused-parens-trait-obj.edition2018.stderr
@@ -0,0 +1,19 @@
+error: unnecessary parentheses around type
+  --> $DIR/unused-parens-trait-obj.rs:25:51
+   |
+LL | pub type DynIsAContextualKeywordIn2015B = Box<dyn (::std::ops::Fn())>;
+   |                                                   ^                ^
+   |
+note: the lint level is defined here
+  --> $DIR/unused-parens-trait-obj.rs:7:9
+   |
+LL | #![deny(unused_parens)]
+   |         ^^^^^^^^^^^^^
+help: remove these parentheses
+   |
+LL - pub type DynIsAContextualKeywordIn2015B = Box<dyn (::std::ops::Fn())>;
+LL + pub type DynIsAContextualKeywordIn2015B = Box<dyn ::std::ops::Fn()>;
+   |
+
+error: aborting due to 1 previous error
+
diff --git a/tests/ui/lint/unused/unused-parens-trait-obj.rs b/tests/ui/lint/unused/unused-parens-trait-obj.rs
new file mode 100644
index 00000000000..2192baa2e02
--- /dev/null
+++ b/tests/ui/lint/unused/unused-parens-trait-obj.rs
@@ -0,0 +1,27 @@
+//@ revisions: edition2015 edition2018
+//@[edition2015] check-pass
+//@[edition2015] edition: 2015
+//@[edition2018] run-rustfix
+//@[edition2018] edition: 2018
+
+#![deny(unused_parens)]
+
+#[allow(unused)]
+macro_rules! edition2015_only {
+    () => {
+        mod dyn {
+            pub type IsAContextualKeywordIn2015 = ();
+        }
+
+        pub type DynIsAContextualKeywordIn2015A = dyn::IsAContextualKeywordIn2015;
+    }
+}
+
+#[cfg(edition2015)]
+edition2015_only!();
+
+// there's a lint for 2018 and later only because of how dyn is parsed in edition 2015
+//[edition2018]~v ERROR unnecessary parentheses around type
+pub type DynIsAContextualKeywordIn2015B = Box<dyn (::std::ops::Fn())>;
+
+fn main() {}
diff --git a/tests/ui/sanitizer/cfi/closures.rs b/tests/ui/sanitizer/cfi/closures.rs
index 9f9002da674..424e70560db 100644
--- a/tests/ui/sanitizer/cfi/closures.rs
+++ b/tests/ui/sanitizer/cfi/closures.rs
@@ -31,7 +31,7 @@ fn dyn_fn_with_params() {
 
 #[test]
 fn call_fn_trait() {
-   let f: &(dyn Fn()) = &(|| {}) as _;
+   let f: &dyn Fn() = &(|| {}) as _;
    f.call(());
 }
 
@@ -47,7 +47,7 @@ fn use_fnmut<F: FnMut()>(mut f: F) {
 
 #[test]
 fn fn_to_fnmut() {
-    let f: &(dyn Fn()) = &(|| {}) as _;
+    let f: &dyn Fn() = &(|| {}) as _;
     use_fnmut(f);
 }
 
diff --git a/tests/ui/traits/dyn-trait.rs b/tests/ui/traits/dyn-trait.rs
index 4fb7aea5cba..a378ce5a696 100644
--- a/tests/ui/traits/dyn-trait.rs
+++ b/tests/ui/traits/dyn-trait.rs
@@ -7,7 +7,7 @@ static BYTE: u8 = 33;
 fn main() {
     let x: &(dyn 'static + Display) = &BYTE;
     let y: Box<dyn Display + 'static> = Box::new(BYTE);
-    let _: &dyn (Display) = &BYTE;
+    let _: &dyn Display = &BYTE;
     let _: &dyn (::std::fmt::Display) = &BYTE;
     let xstr = format!("{}", x);
     let ystr = format!("{}", y);
diff --git a/tests/ui/traits/impl-2.rs b/tests/ui/traits/impl-2.rs
index 41fa1cd334f..eafbaeaa167 100644
--- a/tests/ui/traits/impl-2.rs
+++ b/tests/ui/traits/impl-2.rs
@@ -10,7 +10,7 @@ pub mod Foo {
 }
 
 mod Bar {
-    impl<'a> dyn (crate::Foo::Trait) + 'a {
+    impl<'a> dyn crate::Foo::Trait + 'a {
         fn bar(&self) { self.foo() }
     }
 }