Auto merge of rust-lang#117204 - nnethercote:rustc_ast_passes, r=compiler-errors

Minor improvements to `rustc_ast_passes`

Some improvements I found while looking at this code.

r? `@compiler-errors`

Author: bors

Cargo.lock

@@ -3512,7 +3512,6 @@ dependencies = [
  "rustc_span",
  "rustc_target",
  "thin-vec",
- "tracing",
 ]
 
 [[package]]

compiler/rustc_ast_passes/Cargo.toml

@@ -19,5 +19,4 @@ rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
 rustc_target = { path = "../rustc_target" }
 thin-vec = "0.2.12"
-tracing = "0.1"
 # tidy-alphabetical-end

compiler/rustc_ast_passes/src/ast_validation.rs

@@ -1442,62 +1442,54 @@ fn deny_equality_constraints(
     let mut err = errors::EqualityInWhere { span: predicate.span, assoc: None, assoc2: None };
 
     // Given `<A as Foo>::Bar = RhsTy`, suggest `A: Foo<Bar = RhsTy>`.
-    if let TyKind::Path(Some(qself), full_path) = &predicate.lhs_ty.kind {
-        if let TyKind::Path(None, path) = &qself.ty.kind {
-            match &path.segments[..] {
-                [PathSegment { ident, args: None, .. }] => {
-                    for param in &generics.params {
-                        if param.ident == *ident {
-                            let param = ident;
-                            match &full_path.segments[qself.position..] {
-                                [PathSegment { ident, args, .. }] => {
-                                    // Make a new `Path` from `foo::Bar` to `Foo<Bar = RhsTy>`.
-                                    let mut assoc_path = full_path.clone();
-                                    // Remove `Bar` from `Foo::Bar`.
-                                    assoc_path.segments.pop();
-                                    let len = assoc_path.segments.len() - 1;
-                                    let gen_args = args.as_deref().cloned();
-                                    // Build `<Bar = RhsTy>`.
-                                    let arg = AngleBracketedArg::Constraint(AssocConstraint {
-                                        id: rustc_ast::node_id::DUMMY_NODE_ID,
-                                        ident: *ident,
-                                        gen_args,
-                                        kind: AssocConstraintKind::Equality {
-                                            term: predicate.rhs_ty.clone().into(),
-                                        },
-                                        span: ident.span,
-                                    });
-                                    // Add `<Bar = RhsTy>` to `Foo`.
-                                    match &mut assoc_path.segments[len].args {
-                                        Some(args) => match args.deref_mut() {
-                                            GenericArgs::Parenthesized(_) => continue,
-                                            GenericArgs::AngleBracketed(args) => {
-                                                args.args.push(arg);
-                                            }
-                                        },
-                                        empty_args => {
-                                            *empty_args = Some(
-                                                AngleBracketedArgs {
-                                                    span: ident.span,
-                                                    args: thin_vec![arg],
-                                                }
-                                                .into(),
-                                            );
-                                        }
-                                    }
-                                    err.assoc = Some(errors::AssociatedSuggestion {
-                                        span: predicate.span,
-                                        ident: *ident,
-                                        param: *param,
-                                        path: pprust::path_to_string(&assoc_path),
-                                    })
-                                }
-                                _ => {}
-                            };
+    if let TyKind::Path(Some(qself), full_path) = &predicate.lhs_ty.kind
+        && let TyKind::Path(None, path) = &qself.ty.kind
+        && let [PathSegment { ident, args: None, .. }] = &path.segments[..]
+    {
+        for param in &generics.params {
+            if param.ident == *ident
+                && let [PathSegment { ident, args, .. }] = &full_path.segments[qself.position..]
+            {
+                // Make a new `Path` from `foo::Bar` to `Foo<Bar = RhsTy>`.
+                let mut assoc_path = full_path.clone();
+                // Remove `Bar` from `Foo::Bar`.
+                assoc_path.segments.pop();
+                let len = assoc_path.segments.len() - 1;
+                let gen_args = args.as_deref().cloned();
+                // Build `<Bar = RhsTy>`.
+                let arg = AngleBracketedArg::Constraint(AssocConstraint {
+                    id: rustc_ast::node_id::DUMMY_NODE_ID,
+                    ident: *ident,
+                    gen_args,
+                    kind: AssocConstraintKind::Equality {
+                        term: predicate.rhs_ty.clone().into(),
+                    },
+                    span: ident.span,
+                });
+                // Add `<Bar = RhsTy>` to `Foo`.
+                match &mut assoc_path.segments[len].args {
+                    Some(args) => match args.deref_mut() {
+                        GenericArgs::Parenthesized(_) => continue,
+                        GenericArgs::AngleBracketed(args) => {
+                            args.args.push(arg);
                         }
+                    },
+                    empty_args => {
+                        *empty_args = Some(
+                            AngleBracketedArgs {
+                                span: ident.span,
+                                args: thin_vec![arg],
+                            }
+                            .into(),
+                        );
                     }
                 }
-                _ => {}
+                err.assoc = Some(errors::AssociatedSuggestion {
+                    span: predicate.span,
+                    ident: *ident,
+                    param: param.ident,
+                    path: pprust::path_to_string(&assoc_path),
+                })
             }
         }
     }