parser: misc small item related improvements & cleanups.

Author: Centril

src/librustc_parse/parser/item.rs

@@ -572,6 +572,11 @@ impl<'a> Parser<'a> {
         if !self.eat_keyword(kw) { self.unexpected() } else { Ok(()) }
     }
 
+    /// Is the given keyword `kw` followed by a non-reserved identifier?
+    fn is_kw_followed_by_ident(&self, kw: Symbol) -> bool {
+        self.token.is_keyword(kw) && self.look_ahead(1, |t| t.is_ident() && !t.is_reserved_ident())
+    }
+
     fn check_or_expected(&mut self, ok: bool, typ: TokenType) -> bool {
         if ok {
             true

src/librustc_parse/parser/mod.rs

@@ -8,7 +8,7 @@ use crate::DirectoryOwnership;
 
 use rustc_errors::{Applicability, PResult};
 use rustc_span::source_map::{BytePos, Span};
-use rustc_span::symbol::{kw, sym, Symbol};
+use rustc_span::symbol::{kw, sym};
 use syntax::ast;
 use syntax::ast::{AttrStyle, AttrVec, Attribute, Mac, MacStmtStyle};
 use syntax::ast::{Block, BlockCheckMode, Expr, ExprKind, Local, Stmt, StmtKind, DUMMY_NODE_ID};
@@ -55,13 +55,11 @@ impl<'a> Parser<'a> {
             return self.recover_stmt_local(lo, attrs.into(), msg, "let");
         }
 
-        // Starts like a simple path, being careful to avoid contextual keywords
-        // such as a union items, item with `crate` visibility or auto trait items.
-        // Our goal here is to parse an arbitrary path `a::b::c` but not something that starts
-        // like a path (1 token), but it fact not a path.
-        if self.token.is_path_start()
-            && !self.token.is_qpath_start()
-            && !self.is_path_start_item() // Confirm we don't steal syntax from `parse_item_`.
+        // Starts like a simple path, being careful to avoid contextual keywords,
+        // e.g., `union`, items with `crate` visibility, or `auto trait` items.
+        // We aim to parse an arbitrary path `a::b` but not something that starts like a path
+        // (1 token), but it fact not a path. Also, we avoid stealing syntax from `parse_item_`.
+        if self.token.is_path_start() && !self.token.is_qpath_start() && !self.is_path_start_item()
         {
             let path = self.parse_path(PathStyle::Expr)?;
 
@@ -191,10 +189,6 @@ impl<'a> Parser<'a> {
         }
     }
 
-    fn is_kw_followed_by_ident(&self, kw: Symbol) -> bool {
-        self.token.is_keyword(kw) && self.look_ahead(1, |t| t.is_ident() && !t.is_reserved_ident())
-    }
-
     fn recover_stmt_local(
         &mut self,
         lo: Span,

src/librustc_parse/parser/stmt.rs

@@ -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
 

src/test/ui/issues/issue-58856-2.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> {

src/test/ui/issues/issue-60075.stderr

@@ -1,6 +1,7 @@
 macro_rules! m {
+    //~^ ERROR missing `fn`, `type`, or `static` for extern-item declaration
     () => {
-        let //~ ERROR expected
+        let
     };
 }
 

src/test/ui/macros/issue-54441.rs

@@ -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
 

src/test/ui/macros/issue-54441.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
 

src/test/ui/parser/attr-before-eof.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
 

src/test/ui/parser/attr-dangling-in-mod.stderr

@@ -1,8 +1,8 @@
 error: expected item after attributes
-  --> $DIR/attrs-after-extern-mod.rs:6:19
+  --> $DIR/attrs-after-extern-mod.rs:6:5
    |
 LL |     #[cfg(stage37)]
-   |                   ^
+   |     ^^^^^^^^^^^^^^^
 
 error: aborting due to previous error