Rollup merge of #68728 - Centril:towards-fn-merge, r=petrochenkov

parse: merge `fn` syntax + cleanup item parsing

Here we continue the work in https://github.com/rust-lang/rust/pull/67131 in particular to merge the grammars of `fn` items in various positions.

A list of *language level* changes (as sanctioned by the language team in https://github.com/rust-lang/rust/issues/65041#issuecomment-538105286 and https://github.com/rust-lang/rust/pull/67131):

- `self` parameters are now *syntactically* allowed as the first parameter irrespective of item context (and in function pointers). Instead, semantic validation (`ast_validation`) is used.

- Syntactically, `fn` items in `extern { ... }` blocks can now have bodies (`fn foo() { ... }` as opposed to `fn foo();`). As above, we use semantic restrictions instead.

- Syntactically, `fn` items in free contexts (directly in a file or a module) can now be without bodies (`fn foo();` as opposed to `fn foo() { ... }`. As above, we use semantic restrictions instead, including for non-ident parameter patterns.

- `const extern fn` feature gating is now done post-expansion such that we do not have conditional compatibilities of function qualifiers *in parsing*.

- The `FnFrontMatter` grammar becomes:
   ```rust
   Extern = "extern" StringLit ;
   FnQual = "const"? "async"? "unsafe"? Extern? ;
   FnFrontMatter = FnQual "fn" ;
   ```

   That is, all item contexts now *syntactically* allow `const async unsafe extern "C" fn` and use semantic restrictions to rule out combinations previously prevented syntactically. The semantic restrictions include in particular:

   - `fn`s in `extern { ... }` can have no qualifiers.
   - `const` and `async` cannot be combined.

- To fuse the list-of-items parsing in the 4 contexts that items are allowed, we now must permit inner attributes (`#![attr]`) inside `trait Foo { ... }` definitions. That is, we now allow e.g. `trait Foo { #![attr] }`. This was probably an oversight due to not using a uniform parsing mechanism, which we now do have (`fn parse_item_list`). The semantic support (including e.g. for linting) falls out directly from the attributes infrastructure. To ensure this, we include a test for lints.

Put together, these grammar changes allow us to substantially reduce the complexity of item parsing and its grammar. There are however some other non-language improvements that allow the compression to take place.

A list of *compiler-internal* changes (in particular noting the parser-external data-structure changes):

- We use `enum AllowPlus/RecoverQPath/AllowCVariadic { Yes, No }` in `parser/ty.rs` instead of passing around 3 different `bool`s. I felt this was necessary as it was becoming mentally taxing to track which-is-which.

- `fn visit_trait_item` and `fn visit_impl_item` are merged into `fn visit_assoc_item` which now is passed an `AssocCtxt` to check which one it is.

- We change `FnKind` to:

  ```rust
  pub enum FnKind<'a> {
      Fn(FnCtxt, Ident, &'a FnSig, &'a Visibility, Option<&'a Block>),
      Closure(&'a FnDecl, &'a Expr),
  }
  ```

  with:

  ```rust
  pub enum FnCtxt {
      Free,
      Foreign,
      Assoc(AssocCtxt),
  }
  ```

  This is then taken advantage of in tweaking the various semantic restrictions as well as in pretty printing.

- In `ItemKind::Fn`, we change `P<Block>` to `Option<P<Block>>`.

- In `ForeignItemKind::Fn`, we change `P<FnDecl>` to `FnSig` and `P<Block>` to `Option<P<Block>>`.

- We change `ast::{Unsafety, Spanned<Constness>}>` into `enum ast::{Unsafe, Const} { Yes(Span), No }` respectively. This change in formulation allow us to exclude `Span` in the case of `No`, which facilitates parsing. Moreover, we also add a `Span` to `IsAsync` which is renamed to `Async`. The new `Span`s in `Unsafety` and `Async` are then taken advantage of for better diagnostics. A reason this change was made is to have a more uniform and clear naming scheme.

  The HIR keeps the structures in AST (with those definitions moved into HIR) for now to avoid regressing perf.

- Various cleanups, bug fixes, and diagnostics improvements are made along the way. It is probably best to understand those via the diffs.

I would recommend reviewing this commit-by-commit with whitespace changes hidden.

r? @estebank @petrochenkov

40 files changed, 142 insertions, 114 deletions

diff --git a/src/test/pretty/trait-inner-attr.rs b/src/test/pretty/trait-inner-attr.rs
new file mode 100644
index 00000000000..bb4fb1459bd
--- /dev/null
+++ b/src/test/pretty/trait-inner-attr.rs
@@ -0,0 +1,7 @@
+// pp-exact
+
+trait Foo {
+    #![allow(bar)]
+}
+
+fn main() { }
diff --git a/src/test/ui/issues/issue-58856-2.stderr b/src/test/ui/issues/issue-58856-2.stderr
index 01d70d861e2..6221b90b31d 100644
--- a/src/test/ui/issues/issue-58856-2.stderr
+++ b/src/test/ui/issues/issue-58856-2.stderr
@@ -7,11 +7,11 @@ LL |     fn how_are_you(&self -> Empty {
    |                   |     help: `)` may belong here
    |                   unclosed delimiter
 
-error: expected one of `async`, `const`, `crate`, `default`, `extern`, `fn`, `pub`, `type`, `unsafe`, or `}`, found `)`
+error: expected one of `async`, `const`, `crate`, `default`, `extern`, `fn`, `pub`, `type`, `unsafe`, `}`, or identifier, found `)`
   --> $DIR/issue-58856-2.rs:11:1
    |
 LL |     }
-   |      - expected one of 10 possible tokens
+   |      - expected one of 11 possible tokens
 LL | }
    | ^ unexpected token
 
diff --git a/src/test/ui/issues/issue-60075.stderr b/src/test/ui/issues/issue-60075.stderr
index 60eb99b46b7..b2beb73503b 100644
--- a/src/test/ui/issues/issue-60075.stderr
+++ b/src/test/ui/issues/issue-60075.stderr
@@ -4,7 +4,7 @@ error: expected one of `.`, `;`, `?`, `else`, or an operator, found `}`
 LL |         });
    |          ^ expected one of `.`, `;`, `?`, `else`, or an operator
 
-error: expected one of `async`, `const`, `crate`, `default`, `extern`, `fn`, `pub`, `type`, `unsafe`, or `}`, found `;`
+error: expected one of `async`, `const`, `crate`, `default`, `extern`, `fn`, `pub`, `type`, `unsafe`, `}`, or identifier, found `;`
   --> $DIR/issue-60075.rs:6:11
    |
 LL |     fn qux() -> Option<usize> {
diff --git a/src/test/ui/macros/issue-54441.rs b/src/test/ui/macros/issue-54441.rs
index afdf76b7b58..a70163df1cb 100644
--- a/src/test/ui/macros/issue-54441.rs
+++ b/src/test/ui/macros/issue-54441.rs
@@ -1,6 +1,7 @@
 macro_rules! m {
+    //~^ ERROR missing `fn`, `type`, or `static` for extern-item declaration
     () => {
-        let //~ ERROR expected
+        let
     };
 }
 
diff --git a/src/test/ui/macros/issue-54441.stderr b/src/test/ui/macros/issue-54441.stderr
index c94355f4716..761e7aec723 100644
--- a/src/test/ui/macros/issue-54441.stderr
+++ b/src/test/ui/macros/issue-54441.stderr
@@ -1,13 +1,11 @@
-error: expected one of `async`, `const`, `crate`, `extern`, `fn`, `pub`, `static`, `type`, or `unsafe`, found keyword `let`
-  --> $DIR/issue-54441.rs:3:9
+error: missing `fn`, `type`, or `static` for extern-item declaration
+  --> $DIR/issue-54441.rs:1:1
    |
-LL |         let
-   |         ^^^ expected one of 9 possible tokens
-...
-LL |     m!();
-   |     ----- in this macro invocation
-   |
-   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
+LL | / macro_rules! m {
+LL | |
+LL | |     () => {
+LL | |         let
+   | |________^ missing `fn`, `type`, or `static`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/parser/attr-before-eof.stderr b/src/test/ui/parser/attr-before-eof.stderr
index eb5daf84981..a2acb94372b 100644
--- a/src/test/ui/parser/attr-before-eof.stderr
+++ b/src/test/ui/parser/attr-before-eof.stderr
@@ -1,8 +1,8 @@
 error: expected item after attributes
-  --> $DIR/attr-before-eof.rs:3:16
+  --> $DIR/attr-before-eof.rs:3:1
    |
 LL | #[derive(Debug)]
-   |                ^
+   | ^^^^^^^^^^^^^^^^
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/parser/attr-dangling-in-mod.stderr b/src/test/ui/parser/attr-dangling-in-mod.stderr
index d896b61ce49..1c892eac08f 100644
--- a/src/test/ui/parser/attr-dangling-in-mod.stderr
+++ b/src/test/ui/parser/attr-dangling-in-mod.stderr
@@ -1,8 +1,8 @@
 error: expected item after attributes
-  --> $DIR/attr-dangling-in-mod.rs:6:14
+  --> $DIR/attr-dangling-in-mod.rs:6:1
    |
 LL | #[foo = "bar"]
-   |              ^
+   | ^^^^^^^^^^^^^^
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/parser/attrs-after-extern-mod.rs b/src/test/ui/parser/attrs-after-extern-mod.rs
index 4bdd16471cd..ea899dca7b2 100644
--- a/src/test/ui/parser/attrs-after-extern-mod.rs
+++ b/src/test/ui/parser/attrs-after-extern-mod.rs
@@ -1,13 +1,7 @@
-// Constants (static variables) can be used to match in patterns, but mutable
-// statics cannot. This ensures that there's some form of error if this is
-// attempted.
+// Make sure there's an error when given `extern { ... #[attr] }`.
 
-extern crate libc;
+fn main() {}
 
 extern {
-    static mut rust_dbg_static_mut: libc::c_int;
-    pub fn rust_dbg_static_mut_check_four();
     #[cfg(stage37)] //~ ERROR expected item after attributes
 }
-
-pub fn main() {}
diff --git a/src/test/ui/parser/attrs-after-extern-mod.stderr b/src/test/ui/parser/attrs-after-extern-mod.stderr
index cecdab4d631..6060f3afe1e 100644
--- a/src/test/ui/parser/attrs-after-extern-mod.stderr
+++ b/src/test/ui/parser/attrs-after-extern-mod.stderr
@@ -1,8 +1,8 @@
 error: expected item after attributes
-  --> $DIR/attrs-after-extern-mod.rs:10:19
+  --> $DIR/attrs-after-extern-mod.rs:6:5
    |
 LL |     #[cfg(stage37)]
-   |                   ^
+   |     ^^^^^^^^^^^^^^^
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/parser/default.rs b/src/test/ui/parser/default.rs
index 17cd06864bf..65ecb1ebbe9 100644
--- a/src/test/ui/parser/default.rs
+++ b/src/test/ui/parser/default.rs
@@ -19,7 +19,8 @@ impl Foo for u16 {
 }
 
 impl Foo for u32 { //~ ERROR not all trait items implemented, missing: `foo`
-    default pub fn foo<T: Default>() -> T { T::default() } //~ ERROR expected one of
+    default pub fn foo<T: Default>() -> T { T::default() }
+    //~^ ERROR missing `fn`, `type`, or `const` for associated-item declaration
 }
 
 fn main() {}
diff --git a/src/test/ui/parser/default.stderr b/src/test/ui/parser/default.stderr
index dde36cf8dde..ede9e471518 100644
--- a/src/test/ui/parser/default.stderr
+++ b/src/test/ui/parser/default.stderr
@@ -1,8 +1,8 @@
-error: expected one of `async`, `const`, `extern`, `fn`, `type`, or `unsafe`, found keyword `pub`
-  --> $DIR/default.rs:22:13
+error: missing `fn`, `type`, or `const` for associated-item declaration
+  --> $DIR/default.rs:22:12
    |
 LL |     default pub fn foo<T: Default>() -> T { T::default() }
-   |             ^^^ expected one of `async`, `const`, `extern`, `fn`, `type`, or `unsafe`
+   |            ^ missing `fn`, `type`, or `const`
 
 error[E0449]: unnecessary visibility qualifier
   --> $DIR/default.rs:16:5
diff --git a/src/test/ui/parser/doc-before-attr.stderr b/src/test/ui/parser/doc-before-attr.stderr
index 0fae44ce5c8..14fd01af2f9 100644
--- a/src/test/ui/parser/doc-before-attr.stderr
+++ b/src/test/ui/parser/doc-before-attr.stderr
@@ -1,8 +1,10 @@
 error: expected item after attributes
-  --> $DIR/doc-before-attr.rs:4:16
+  --> $DIR/doc-before-attr.rs:4:1
    |
+LL | /// hi
+   | ------ other attributes here
 LL | #[derive(Debug)]
-   |                ^
+   | ^^^^^^^^^^^^^^^^
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/parser/doc-before-extern-rbrace.rs b/src/test/ui/parser/doc-before-extern-rbrace.rs
index 695d4da1dca..040206b80ff 100644
--- a/src/test/ui/parser/doc-before-extern-rbrace.rs
+++ b/src/test/ui/parser/doc-before-extern-rbrace.rs
@@ -1,4 +1,6 @@
+fn main() {}
+
 extern {
     /// hi
-    //~^ ERROR expected item after doc comment
+    //~^ ERROR found a documentation comment that doesn't document anything
 }
diff --git a/src/test/ui/parser/doc-before-extern-rbrace.stderr b/src/test/ui/parser/doc-before-extern-rbrace.stderr
index 8cc9c916a7a..0edceb268a7 100644
--- a/src/test/ui/parser/doc-before-extern-rbrace.stderr
+++ b/src/test/ui/parser/doc-before-extern-rbrace.stderr
@@ -1,8 +1,11 @@
-error: expected item after doc comment
-  --> $DIR/doc-before-extern-rbrace.rs:2:5
+error[E0584]: found a documentation comment that doesn't document anything
+  --> $DIR/doc-before-extern-rbrace.rs:4:5
    |
 LL |     /// hi
    |     ^^^^^^ this doc comment doesn't document anything
+   |
+   = help: doc comments must come before what they document, maybe a comment was intended with `//`?
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0584`.
diff --git a/src/test/ui/parser/doc-inside-trait-item.stderr b/src/test/ui/parser/doc-inside-trait-item.stderr
index 261e27b6e0d..246255a0a46 100644
--- a/src/test/ui/parser/doc-inside-trait-item.stderr
+++ b/src/test/ui/parser/doc-inside-trait-item.stderr
@@ -2,7 +2,7 @@ error[E0584]: found a documentation comment that doesn't document anything
   --> $DIR/doc-inside-trait-item.rs:3:5
    |
 LL |     /// empty doc
-   |     ^^^^^^^^^^^^^
+   |     ^^^^^^^^^^^^^ this doc comment doesn't document anything
    |
    = help: doc comments must come before what they document, maybe a comment was intended with `//`?
 
diff --git a/src/test/ui/parser/duplicate-visibility.rs b/src/test/ui/parser/duplicate-visibility.rs
index a8f0b7d61b9..1d271fa64b0 100644
--- a/src/test/ui/parser/duplicate-visibility.rs
+++ b/src/test/ui/parser/duplicate-visibility.rs
@@ -1,4 +1,6 @@
-// error-pattern: expected one of `(`, `async`, `const`, `extern`, `fn`
+fn main() {}
+
 extern {
     pub pub fn foo();
+    //~^ ERROR missing `fn`, `type`, or `static` for extern-item declaration
 }
diff --git a/src/test/ui/parser/duplicate-visibility.stderr b/src/test/ui/parser/duplicate-visibility.stderr
index cba4058e482..36a3a1ed5a0 100644
--- a/src/test/ui/parser/duplicate-visibility.stderr
+++ b/src/test/ui/parser/duplicate-visibility.stderr
@@ -1,8 +1,8 @@
-error: expected one of `(`, `async`, `const`, `extern`, `fn`, `static`, `type`, or `unsafe`, found keyword `pub`
-  --> $DIR/duplicate-visibility.rs:3:9
+error: missing `fn`, `type`, or `static` for extern-item declaration
+  --> $DIR/duplicate-visibility.rs:4:8
    |
 LL |     pub pub fn foo();
-   |         ^^^ expected one of 8 possible tokens
+   |        ^ missing `fn`, `type`, or `static`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/parser/inner-attr-in-trait-def.rs b/src/test/ui/parser/inner-attr-in-trait-def.rs
new file mode 100644
index 00000000000..8dba6b362cd
--- /dev/null
+++ b/src/test/ui/parser/inner-attr-in-trait-def.rs
@@ -0,0 +1,9 @@
+// check-pass
+
+#![deny(non_camel_case_types)]
+
+fn main() {}
+
+trait foo_bar {
+    #![allow(non_camel_case_types)]
+}
diff --git a/src/test/ui/parser/issue-19398.rs b/src/test/ui/parser/issue-19398.rs
index 2158a2fd6c1..982a6be23ac 100644
--- a/src/test/ui/parser/issue-19398.rs
+++ b/src/test/ui/parser/issue-19398.rs
@@ -1,5 +1,6 @@
 trait T {
-    extern "Rust" unsafe fn foo(); //~ ERROR expected one of `async`, `const`
+    //~^ ERROR missing `fn`, `type`, or `const` for associated-item declaration
+    extern "Rust" unsafe fn foo();
 }
 
 fn main() {}
diff --git a/src/test/ui/parser/issue-19398.stderr b/src/test/ui/parser/issue-19398.stderr
index 201a6b2d66a..2bd6ac3a4b3 100644
--- a/src/test/ui/parser/issue-19398.stderr
+++ b/src/test/ui/parser/issue-19398.stderr
@@ -1,10 +1,11 @@
-error: expected one of `async`, `const`, `crate`, `default`, `extern`, `fn`, `pub`, `type`, `unsafe`, or `}`, found keyword `extern`
-  --> $DIR/issue-19398.rs:2:5
+error: missing `fn`, `type`, or `const` for associated-item declaration
+  --> $DIR/issue-19398.rs:1:10
    |
-LL | trait T {
-   |          - expected one of 10 possible tokens
-LL |     extern "Rust" unsafe fn foo();
-   |     ^^^^^^ unexpected token
+LL |   trait T {
+   |  __________^
+LL | |
+LL | |     extern "Rust" unsafe fn foo();
+   | |____^ missing `fn`, `type`, or `const`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/parser/issue-20711-2.rs b/src/test/ui/parser/issue-20711-2.rs
index 0063a334182..168c7e76162 100644
--- a/src/test/ui/parser/issue-20711-2.rs
+++ b/src/test/ui/parser/issue-20711-2.rs
@@ -4,6 +4,7 @@ impl Foo {
     fn foo() {}
 
     #[stable(feature = "rust1", since = "1.0.0")]
-} //~ ERROR expected one of `async`, `const`, `crate`, `default`, `extern`, `fn`, `pub`, `type`, or
+    //~^ ERROR expected item after attributes
+}
 
 fn main() {}
diff --git a/src/test/ui/parser/issue-20711-2.stderr b/src/test/ui/parser/issue-20711-2.stderr
index ee484890fad..10ef31584de 100644
--- a/src/test/ui/parser/issue-20711-2.stderr
+++ b/src/test/ui/parser/issue-20711-2.stderr
@@ -1,10 +1,8 @@
-error: expected one of `async`, `const`, `crate`, `default`, `extern`, `fn`, `pub`, `type`, or `unsafe`, found `}`
-  --> $DIR/issue-20711-2.rs:7:1
+error: expected item after attributes
+  --> $DIR/issue-20711-2.rs:6:5
    |
 LL |     #[stable(feature = "rust1", since = "1.0.0")]
-   |                                                  - expected one of 9 possible tokens
-LL | }
-   | ^ unexpected token
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/parser/issue-20711.rs b/src/test/ui/parser/issue-20711.rs
index dc216167b8a..020bb79d6e7 100644
--- a/src/test/ui/parser/issue-20711.rs
+++ b/src/test/ui/parser/issue-20711.rs
@@ -2,6 +2,7 @@ struct Foo;
 
 impl Foo {
     #[stable(feature = "rust1", since = "1.0.0")]
-} //~ ERROR expected one of `async`, `const`, `crate`, `default`, `extern`, `fn`, `pub`, `type`, or
+    //~^ ERROR expected item after attributes
+}
 
 fn main() {}
diff --git a/src/test/ui/parser/issue-20711.stderr b/src/test/ui/parser/issue-20711.stderr
index 152c9f1c689..66768de5694 100644
--- a/src/test/ui/parser/issue-20711.stderr
+++ b/src/test/ui/parser/issue-20711.stderr
@@ -1,10 +1,8 @@
-error: expected one of `async`, `const`, `crate`, `default`, `extern`, `fn`, `pub`, `type`, or `unsafe`, found `}`
-  --> $DIR/issue-20711.rs:5:1
+error: expected item after attributes
+  --> $DIR/issue-20711.rs:4:5
    |
 LL |     #[stable(feature = "rust1", since = "1.0.0")]
-   |                                                  - expected one of 9 possible tokens
-LL | }
-   | ^ unexpected token
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/parser/issue-32446.stderr b/src/test/ui/parser/issue-32446.stderr
index 1a97f54160b..25c1efe35ae 100644
--- a/src/test/ui/parser/issue-32446.stderr
+++ b/src/test/ui/parser/issue-32446.stderr
@@ -1,8 +1,8 @@
-error: expected one of `async`, `const`, `crate`, `default`, `extern`, `fn`, `pub`, `type`, `unsafe`, or `}`, found `...`
+error: expected one of `async`, `const`, `crate`, `default`, `extern`, `fn`, `pub`, `type`, `unsafe`, `}`, or identifier, found `...`
   --> $DIR/issue-32446.rs:4:11
    |
 LL | trait T { ... }
-   |           ^^^ expected one of 10 possible tokens
+   |           ^^^ expected one of 11 possible tokens
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/parser/issue-41155.stderr b/src/test/ui/parser/issue-41155.stderr
index 0e191eb7e0a..327bc65818f 100644
--- a/src/test/ui/parser/issue-41155.stderr
+++ b/src/test/ui/parser/issue-41155.stderr
@@ -1,8 +1,8 @@
-error: expected one of `(`, `async`, `const`, `default`, `extern`, `fn`, `type`, or `unsafe`, found `}`
+error: expected one of `(`, `async`, `const`, `default`, `extern`, `fn`, `type`, `unsafe`, or identifier, found `}`
   --> $DIR/issue-41155.rs:5:1
    |
 LL |     pub
-   |        - expected one of 8 possible tokens
+   |        - expected one of 9 possible tokens
 LL | }
    | ^ unexpected token
 
diff --git a/src/test/ui/parser/issue-58094-missing-right-square-bracket.stderr b/src/test/ui/parser/issue-58094-missing-right-square-bracket.stderr
index 00f6652b311..8a44ee761ed 100644
--- a/src/test/ui/parser/issue-58094-missing-right-square-bracket.stderr
+++ b/src/test/ui/parser/issue-58094-missing-right-square-bracket.stderr
@@ -7,10 +7,10 @@ LL | #[Ѕ
    |  unclosed delimiter
 
 error: expected item after attributes
-  --> $DIR/issue-58094-missing-right-square-bracket.rs:4:4
+  --> $DIR/issue-58094-missing-right-square-bracket.rs:4:1
    |
 LL | #[Ѕ
-   |    ^
+   | ^^^
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/parser/macro/pub-item-macro.rs b/src/test/ui/parser/macro/pub-item-macro.rs
index bae90227c62..f5f8a01e6a4 100644
--- a/src/test/ui/parser/macro/pub-item-macro.rs
+++ b/src/test/ui/parser/macro/pub-item-macro.rs
@@ -1,12 +1,15 @@
 // Issue #14660
 
-macro_rules! priv_x { () => {
-    static x: u32 = 0;
-}}
+macro_rules! priv_x {
+    () => {
+        static x: u32 = 0;
+    };
+}
 
 macro_rules! pub_x { () => {
     pub priv_x!(); //~ ERROR can't qualify macro invocation with `pub`
-    //~^ HELP try adjusting the macro to put `pub` inside the invocation
+    //~^ HELP remove the visibility
+    //~| HELP try adjusting the macro to put `pub` inside the invocation
 }}
 
 mod foo {
diff --git a/src/test/ui/parser/macro/pub-item-macro.stderr b/src/test/ui/parser/macro/pub-item-macro.stderr
index 49644cf6a0e..4ff96532e03 100644
--- a/src/test/ui/parser/macro/pub-item-macro.stderr
+++ b/src/test/ui/parser/macro/pub-item-macro.stderr
@@ -1,8 +1,8 @@
 error: can't qualify macro invocation with `pub`
-  --> $DIR/pub-item-macro.rs:8:5
+  --> $DIR/pub-item-macro.rs:10:5
    |
 LL |     pub priv_x!();
-   |     ^^^
+   |     ^^^ help: remove the visibility
 ...
 LL |     pub_x!();
    |     --------- in this macro invocation
@@ -11,16 +11,16 @@ LL |     pub_x!();
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0603]: static `x` is private
-  --> $DIR/pub-item-macro.rs:17:23
+  --> $DIR/pub-item-macro.rs:20:23
    |
 LL |     let y: u32 = foo::x;
    |                       ^ this static is private
    |
 note: the static `x` is defined here
-  --> $DIR/pub-item-macro.rs:4:5
+  --> $DIR/pub-item-macro.rs:5:9
    |
-LL |     static x: u32 = 0;
-   |     ^^^^^^^^^^^^^^^^^^
+LL |         static x: u32 = 0;
+   |         ^^^^^^^^^^^^^^^^^^
 ...
 LL |     pub_x!();
    |     --------- in this macro invocation
diff --git a/src/test/ui/parser/macro/trait-non-item-macros.stderr b/src/test/ui/parser/macro/trait-non-item-macros.stderr
index 5a89b5b936f..9d05e85bcc0 100644
--- a/src/test/ui/parser/macro/trait-non-item-macros.stderr
+++ b/src/test/ui/parser/macro/trait-non-item-macros.stderr
@@ -1,8 +1,8 @@
-error: expected one of `async`, `const`, `crate`, `default`, `extern`, `fn`, `pub`, `type`, or `unsafe`, found `2`
+error: expected one of `async`, `const`, `crate`, `default`, `extern`, `fn`, `pub`, `type`, `unsafe`, or identifier, found `2`
   --> $DIR/trait-non-item-macros.rs:2:19
    |
 LL |     ($a:expr) => ($a)
-   |                   ^^ expected one of 9 possible tokens
+   |                   ^^ expected one of 10 possible tokens
 ...
 LL |     bah!(2);
    |     -------- in this macro invocation
diff --git a/src/test/ui/parser/mismatched-braces/missing-close-brace-in-impl-trait.rs b/src/test/ui/parser/mismatched-braces/missing-close-brace-in-impl-trait.rs
index 9f02a7a997b..592215030f5 100644
--- a/src/test/ui/parser/mismatched-braces/missing-close-brace-in-impl-trait.rs
+++ b/src/test/ui/parser/mismatched-braces/missing-close-brace-in-impl-trait.rs
@@ -1,12 +1,14 @@
+fn main() {}
+
 impl T for () { //~ ERROR cannot find trait `T` in this scope
 
 fn foo(&self) {}
+//~^ ERROR missing `fn`, `type`, or `const`
 
-trait T { //~ ERROR expected one of
+trait T {
     fn foo(&self);
 }
 
 pub(crate) struct Bar<T>();
 
-fn main() {}
 //~ ERROR this file contains an unclosed delimiter
diff --git a/src/test/ui/parser/mismatched-braces/missing-close-brace-in-impl-trait.stderr b/src/test/ui/parser/mismatched-braces/missing-close-brace-in-impl-trait.stderr
index a23cfeac58f..1ec54525105 100644
--- a/src/test/ui/parser/mismatched-braces/missing-close-brace-in-impl-trait.stderr
+++ b/src/test/ui/parser/mismatched-braces/missing-close-brace-in-impl-trait.stderr
@@ -1,5 +1,5 @@
 error: this file contains an unclosed delimiter
-  --> $DIR/missing-close-brace-in-impl-trait.rs:12:52
+  --> $DIR/missing-close-brace-in-impl-trait.rs:14:52
    |
 LL | impl T for () {
    |               - unclosed delimiter
@@ -7,23 +7,18 @@ LL | impl T for () {
 LL |
    |                                                    ^
 
-error: expected one of `async`, `const`, `crate`, `default`, `extern`, `fn`, `pub`, `type`, `unsafe`, or `}`, found keyword `trait`
-  --> $DIR/missing-close-brace-in-impl-trait.rs:5:1
+error: missing `fn`, `type`, or `const` for associated-item declaration
+  --> $DIR/missing-close-brace-in-impl-trait.rs:5:17
    |
-LL | impl T for () {
-   |               - unclosed delimiter
-LL | 
-LL | fn foo(&self) {}
-   |                 -
-   |                 |
-   |                 expected one of 10 possible tokens
-   |                 help: `}` may belong here
-LL | 
-LL | trait T {
-   | ^^^^^ unexpected token
+LL |   fn foo(&self) {}
+   |  _________________^
+LL | |
+LL | |
+LL | | trait T {
+   | |_ missing `fn`, `type`, or `const`
 
 error[E0405]: cannot find trait `T` in this scope
-  --> $DIR/missing-close-brace-in-impl-trait.rs:1:6
+  --> $DIR/missing-close-brace-in-impl-trait.rs:3:6
    |
 LL | impl T for () {
    |      ^ not found in this scope
diff --git a/src/test/ui/parser/mismatched-braces/missing-close-brace-in-trait.rs b/src/test/ui/parser/mismatched-braces/missing-close-brace-in-trait.rs
index 5ec5d45bbe7..077e3347194 100644
--- a/src/test/ui/parser/mismatched-braces/missing-close-brace-in-trait.rs
+++ b/src/test/ui/parser/mismatched-braces/missing-close-brace-in-trait.rs
@@ -3,7 +3,7 @@ trait T {
     fn foo(&self);
 
 pub(crate) struct Bar<T>();
-//~^ ERROR expected one of
+//~^ ERROR missing `fn`, `type`, or `const`
 
 impl T for Bar<usize> {
 fn foo(&self) {}
diff --git a/src/test/ui/parser/mismatched-braces/missing-close-brace-in-trait.stderr b/src/test/ui/parser/mismatched-braces/missing-close-brace-in-trait.stderr
index 21364012782..1bb153c461d 100644
--- a/src/test/ui/parser/mismatched-braces/missing-close-brace-in-trait.stderr
+++ b/src/test/ui/parser/mismatched-braces/missing-close-brace-in-trait.stderr
@@ -7,11 +7,11 @@ LL | trait T {
 LL | fn main() {}
    |                                                                 ^
 
-error: expected one of `async`, `const`, `default`, `extern`, `fn`, `type`, or `unsafe`, found keyword `struct`
-  --> $DIR/missing-close-brace-in-trait.rs:5:12
+error: missing `fn`, `type`, or `const` for associated-item declaration
+  --> $DIR/missing-close-brace-in-trait.rs:5:11
    |
 LL | pub(crate) struct Bar<T>();
-   |            ^^^^^^ expected one of 7 possible tokens
+   |           ^ missing `fn`, `type`, or `const`
 
 error[E0601]: `main` function not found in crate `missing_close_brace_in_trait`
   --> $DIR/missing-close-brace-in-trait.rs:1:1
diff --git a/src/test/ui/parser/pub-method-macro.rs b/src/test/ui/parser/pub-method-macro.rs
index f04af1a0d65..0183bdcf622 100644
--- a/src/test/ui/parser/pub-method-macro.rs
+++ b/src/test/ui/parser/pub-method-macro.rs
@@ -15,7 +15,8 @@ mod bleh {
 
     impl S {
         pub defn!(f); //~ ERROR can't qualify macro invocation with `pub`
-        //~^ HELP try adjusting the macro to put `pub` inside the invocation
+        //~^ HELP remove the visibility
+        //~| HELP try adjusting the macro to put `pub` inside the invocation
     }
 }
 
diff --git a/src/test/ui/parser/pub-method-macro.stderr b/src/test/ui/parser/pub-method-macro.stderr
index 7b0fe493461..7c7a909267a 100644
--- a/src/test/ui/parser/pub-method-macro.stderr
+++ b/src/test/ui/parser/pub-method-macro.stderr
@@ -2,7 +2,7 @@ error: can't qualify macro invocation with `pub`
   --> $DIR/pub-method-macro.rs:17:9
    |
 LL |         pub defn!(f);
-   |         ^^^
+   |         ^^^ help: remove the visibility
    |
    = help: try adjusting the macro to put `pub` inside the invocation
 
diff --git a/src/test/ui/parser/removed-syntax-static-fn.rs b/src/test/ui/parser/removed-syntax-static-fn.rs
index 0caddb9855d..9e12222f3fd 100644
--- a/src/test/ui/parser/removed-syntax-static-fn.rs
+++ b/src/test/ui/parser/removed-syntax-static-fn.rs
@@ -1,8 +1,8 @@
 struct S;
 
 impl S {
+    //~^ ERROR missing `fn`, `type`, or `const` for associated-item declaration
     static fn f() {}
-    //~^ ERROR expected one of `async`, `const`, `crate`, `default`, `extern`, `fn`, `pub`, `type`,
 }
 
 fn main() {}
diff --git a/src/test/ui/parser/removed-syntax-static-fn.stderr b/src/test/ui/parser/removed-syntax-static-fn.stderr
index dfadefee23c..5edf88026fb 100644
--- a/src/test/ui/parser/removed-syntax-static-fn.stderr
+++ b/src/test/ui/parser/removed-syntax-static-fn.stderr
@@ -1,10 +1,11 @@
-error: expected one of `async`, `const`, `crate`, `default`, `extern`, `fn`, `pub`, `type`, `unsafe`, or `}`, found keyword `static`
-  --> $DIR/removed-syntax-static-fn.rs:4:5
+error: missing `fn`, `type`, or `const` for associated-item declaration
+  --> $DIR/removed-syntax-static-fn.rs:3:9
    |
-LL | impl S {
-   |         - expected one of 10 possible tokens
-LL |     static fn f() {}
-   |     ^^^^^^ unexpected token
+LL |   impl S {
+   |  _________^
+LL | |
+LL | |     static fn f() {}
+   | |____^ missing `fn`, `type`, or `const`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/pub/pub-restricted-error-fn.rs b/src/test/ui/pub/pub-restricted-error-fn.rs
index 56ee02f517c..3f8904fbe79 100644
--- a/src/test/ui/pub/pub-restricted-error-fn.rs
+++ b/src/test/ui/pub/pub-restricted-error-fn.rs
@@ -1,3 +1,2 @@
-#![feature(pub_restricted)]
-
 pub(crate) () fn foo() {} //~ unmatched visibility
+//~^ ERROR expected item, found `(`
diff --git a/src/test/ui/pub/pub-restricted-error-fn.stderr b/src/test/ui/pub/pub-restricted-error-fn.stderr
index fcff5334890..c0168b02da6 100644
--- a/src/test/ui/pub/pub-restricted-error-fn.stderr
+++ b/src/test/ui/pub/pub-restricted-error-fn.stderr
@@ -1,8 +1,16 @@
-error: unmatched visibility `pub`
-  --> $DIR/pub-restricted-error-fn.rs:3:10
+error: unmatched visibility `pub(crate)`
+  --> $DIR/pub-restricted-error-fn.rs:1:1
    |
 LL | pub(crate) () fn foo() {}
-   |          ^
+   | ^^^^^^^^^^ the unmatched visibility
+   |
+   = help: you likely meant to define an item, e.g., `pub(crate) fn foo() {}`
+
+error: expected item, found `(`
+  --> $DIR/pub-restricted-error-fn.rs:1:12
+   |
+LL | pub(crate) () fn foo() {}
+   |            ^ expected item
 
-error: aborting due to previous error
+error: aborting due to 2 previous errors