Merge pull request #2862 from topecongiro/issue-2852

Preserve parens in trait bounds

src/types.rs

@@ -521,7 +521,24 @@ impl Rewrite for ast::GenericBound {
 
 impl Rewrite for ast::GenericBounds {
     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
-        join_bounds(context, shape, self, true)
+        if self.is_empty() {
+            return Some(String::new());
+        }
+
+        let span = mk_sp(self.get(0)?.span().lo(), self.last()?.span().hi());
+        let has_paren = context.snippet(span).starts_with("(");
+        let bounds_shape = if has_paren {
+            shape.offset_left(1)?.sub_width(1)?
+        } else {
+            shape
+        };
+        join_bounds(context, bounds_shape, self, true).map(|s| {
+            if has_paren {
+                format!("({})", s)
+            } else {
+                s
+            }
+        })
     }
 }
 

tests/source/dyn_trait.rs

@@ -1,5 +1,7 @@
 #![feature(dyn_trait)]
+
 fn main() {
+    // #2506
     // checks rustfmt doesn't remove dyn
     trait MyTrait {
         fn method(&self) -> u64;
@@ -13,4 +15,6 @@ fn main() {
 
     fn f2(a: Box<dyn Very_______________________Long__________________Name____________________Trait+ 'static,>) {}
 
+    // #2582
+    let _: &dyn (::std::any::Any) = &msg;
 }

tests/target/dyn_trait.rs

@@ -1,5 +1,7 @@
 #![feature(dyn_trait)]
+
 fn main() {
+    // #2506
     // checks rustfmt doesn't remove dyn
     trait MyTrait {
         fn method(&self) -> u64;
@@ -19,4 +21,7 @@ fn main() {
         >,
     ) {
     }
+
+    // #2582
+    let _: &dyn (::std::any::Any) = &msg;
 }

tests/target/fn-simple.rs

@@ -107,4 +107,4 @@ pub(crate) fn init() {}
 crate fn init() {}
 
 // #2630
-fn make_map<T, F: Fn(&T) -> String>(records: &Vec<T>, key_fn: F) -> HashMap<String, usize> {}
+fn make_map<T, F: (Fn(&T) -> String)>(records: &Vec<T>, key_fn: F) -> HashMap<String, usize> {}