Rollup merge of #142237 - benschulz:unused-parens-fn, r=fee1-dead

Detect more cases of unused_parens around types

With this change, more unused parentheses around bounds and types nested within bounds are detected.

compiler/rustc_ast/src/ast.rs

@@ -1390,6 +1390,7 @@ impl Expr {
                 path.clone(),
                 TraitBoundModifiers::NONE,
                 self.span,
+                Parens::No,
             ))),
             _ => None,
         }
@@ -3366,6 +3367,13 @@ pub struct TraitRef {
     pub ref_id: NodeId,
 }
 
+/// Whether enclosing parentheses are present or not.
+#[derive(Clone, Encodable, Decodable, Debug)]
+pub enum Parens {
+    Yes,
+    No,
+}
+
 #[derive(Clone, Encodable, Decodable, Debug)]
 pub struct PolyTraitRef {
     /// The `'a` in `for<'a> Foo<&'a T>`.
@@ -3378,6 +3386,10 @@ pub struct PolyTraitRef {
     pub trait_ref: TraitRef,
 
     pub span: Span,
+
+    /// When `Yes`, the first and last character of `span` are an opening
+    /// and a closing paren respectively.
+    pub parens: Parens,
 }
 
 impl PolyTraitRef {
@@ -3386,12 +3398,14 @@ impl PolyTraitRef {
         path: Path,
         modifiers: TraitBoundModifiers,
         span: Span,
+        parens: Parens,
     ) -> Self {
         PolyTraitRef {
             bound_generic_params: generic_params,
             modifiers,
             trait_ref: TraitRef { path, ref_id: DUMMY_NODE_ID },
             span,
+            parens,
         }
     }
 }

compiler/rustc_ast/src/visit.rs

@@ -1142,7 +1142,7 @@ macro_rules! common_visitor_and_walkers {
             vis: &mut V,
             p: &$($lt)? $($mut)? PolyTraitRef,
         ) -> V::Result {
-            let PolyTraitRef { bound_generic_params, modifiers, trait_ref, span } = p;
+            let PolyTraitRef { bound_generic_params, modifiers, trait_ref, span, parens: _ } = p;
             try_visit!(visit_modifiers(vis, modifiers));
             try_visit!(visit_generic_params(vis, bound_generic_params));
             try_visit!(vis.visit_trait_ref(trait_ref));