auto-impl: add feature gate and AST representation

[dingxiangfei2009]

Tracking issue #149556

[rust-log-analyzer]

The job tidy failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

[TIMING:end] tool::ToolBuild { build_compiler: Compiler { stage: 0, host: x86_64-unknown-linux-gnu, forced_compiler: false }, target: x86_64-unknown-linux-gnu, tool: "tidy", path: "src/tools/tidy", mode: ToolBootstrap, source_type: InTree, extra_features: [], allow_features: "", cargo_args: [], artifact_kind: Binary } -- 8.542
[TIMING:end] tool::Tidy { compiler: Compiler { stage: 0, host: x86_64-unknown-linux-gnu, forced_compiler: false }, target: x86_64-unknown-linux-gnu } -- 0.000
fmt check
Diff in /checkout/compiler/rustc_ast/src/ast.rs:4252:
             Use(..) | Static(..) | Const(..) | ConstBlock(..) | Fn(..) | Mod(..)
             | GlobalAsm(..) | TyAlias(..) | Struct(..) | Union(..) | Trait(..) | TraitAlias(..)
             | MacroDef(..) | Delegation(..) | DelegationMac(..) => "a",
-            ExternCrate(..) | ForeignMod(..) | MacCall(..) | Enum(..) | Impl { .. }
+            ExternCrate(..)
+            | ForeignMod(..)
+            | MacCall(..)
+            | Enum(..)
+            | Impl { .. }
             | AutoImplTrait(..) => "an",
         }
     }
fmt: checked 7054 files
Bootstrap failed while executing `test src/tools/tidy tidyselftest --extra-checks=py,cpp,js,spellcheck`
Currently active steps:

[rust-bors]

☔ The latest upstream changes (presumably #161772) made this pull request unmergeable. Please resolve the merge conflicts by rebasing.