Remove `token::{Open,Close}Delim`.

By replacing them with `{Open,Close}{Param,Brace,Bracket,Invisible}`.

PR #137902 made `ast::TokenKind` more like `lexer::TokenKind` by
replacing the compound `BinOp{,Eq}(BinOpToken)` variants with fieldless
variants `Plus`, `Minus`, `Star`, etc. This commit does a similar thing
with delimiters. It also makes `ast::TokenKind` more similar to
`parser::TokenType`.

This requires a few new methods:
- `TokenKind::is_{,open_,close_}delim()` replace various kinds of
  pattern matches.
- `Delimiter::as_{open,close}_token_kind` are used to convert
  `Delimiter` values to `TokenKind`.

Despite these additions, it's a net reduction in lines of code. This is
because e.g. `token::OpenParen` is so much shorter than
`token::OpenDelim(Delimiter::Parenthesis)` that many multi-line forms
reduce to single line forms. And many places where the number of lines
doesn't change are still easier to read, just because the names are
shorter, e.g.:
```
-   } else if self.token != token::CloseDelim(Delimiter::Brace) {
+   } else if self.token != token::CloseBrace {
```

3 files changed, 52 insertions, 59 deletions

diff --git a/compiler/rustc_parse/src/lexer/mod.rs b/compiler/rustc_parse/src/lexer/mod.rs
index 4935fc03256..a8ec9a1e952 100644
--- a/compiler/rustc_parse/src/lexer/mod.rs
+++ b/compiler/rustc_parse/src/lexer/mod.rs
@@ -371,12 +371,12 @@ impl<'psess, 'src> Lexer<'psess, 'src> {
                 rustc_lexer::TokenKind::Semi => token::Semi,
                 rustc_lexer::TokenKind::Comma => token::Comma,
                 rustc_lexer::TokenKind::Dot => token::Dot,
-                rustc_lexer::TokenKind::OpenParen => token::OpenDelim(Delimiter::Parenthesis),
-                rustc_lexer::TokenKind::CloseParen => token::CloseDelim(Delimiter::Parenthesis),
-                rustc_lexer::TokenKind::OpenBrace => token::OpenDelim(Delimiter::Brace),
-                rustc_lexer::TokenKind::CloseBrace => token::CloseDelim(Delimiter::Brace),
-                rustc_lexer::TokenKind::OpenBracket => token::OpenDelim(Delimiter::Bracket),
-                rustc_lexer::TokenKind::CloseBracket => token::CloseDelim(Delimiter::Bracket),
+                rustc_lexer::TokenKind::OpenParen => token::OpenParen,
+                rustc_lexer::TokenKind::CloseParen => token::CloseParen,
+                rustc_lexer::TokenKind::OpenBrace => token::OpenBrace,
+                rustc_lexer::TokenKind::CloseBrace => token::CloseBrace,
+                rustc_lexer::TokenKind::OpenBracket => token::OpenBracket,
+                rustc_lexer::TokenKind::CloseBracket => token::CloseBracket,
                 rustc_lexer::TokenKind::At => token::At,
                 rustc_lexer::TokenKind::Pound => token::Pound,
                 rustc_lexer::TokenKind::Tilde => token::Tilde,
diff --git a/compiler/rustc_parse/src/lexer/tokentrees.rs b/compiler/rustc_parse/src/lexer/tokentrees.rs
index b3f83a32024..0ddd9a85df8 100644
--- a/compiler/rustc_parse/src/lexer/tokentrees.rs
+++ b/compiler/rustc_parse/src/lexer/tokentrees.rs
@@ -18,38 +18,33 @@ impl<'psess, 'src> Lexer<'psess, 'src> {
 
         let mut buf = Vec::new();
         loop {
-            match self.token.kind {
-                token::OpenDelim(delim) => {
-                    // Invisible delimiters cannot occur here because `TokenTreesReader` parses
-                    // code directly from strings, with no macro expansion involved.
-                    debug_assert!(!matches!(delim, Delimiter::Invisible(_)));
-                    buf.push(match self.lex_token_tree_open_delim(delim) {
-                        Ok(val) => val,
-                        Err(errs) => return Err(errs),
-                    })
-                }
-                token::CloseDelim(delim) => {
-                    // Invisible delimiters cannot occur here because `TokenTreesReader` parses
-                    // code directly from strings, with no macro expansion involved.
-                    debug_assert!(!matches!(delim, Delimiter::Invisible(_)));
-                    return if is_delimited {
-                        Ok((open_spacing, TokenStream::new(buf)))
-                    } else {
-                        Err(vec![self.close_delim_err(delim)])
-                    };
-                }
-                token::Eof => {
-                    return if is_delimited {
-                        Err(vec![self.eof_err()])
-                    } else {
-                        Ok((open_spacing, TokenStream::new(buf)))
-                    };
-                }
-                _ => {
-                    // Get the next normal token.
-                    let (this_tok, this_spacing) = self.bump();
-                    buf.push(TokenTree::Token(this_tok, this_spacing));
-                }
+            if let Some(delim) = self.token.kind.open_delim() {
+                // Invisible delimiters cannot occur here because `TokenTreesReader` parses
+                // code directly from strings, with no macro expansion involved.
+                debug_assert!(!matches!(delim, Delimiter::Invisible(_)));
+                buf.push(match self.lex_token_tree_open_delim(delim) {
+                    Ok(val) => val,
+                    Err(errs) => return Err(errs),
+                })
+            } else if let Some(delim) = self.token.kind.close_delim() {
+                // Invisible delimiters cannot occur here because `TokenTreesReader` parses
+                // code directly from strings, with no macro expansion involved.
+                debug_assert!(!matches!(delim, Delimiter::Invisible(_)));
+                return if is_delimited {
+                    Ok((open_spacing, TokenStream::new(buf)))
+                } else {
+                    Err(vec![self.close_delim_err(delim)])
+                };
+            } else if self.token.kind == token::Eof {
+                return if is_delimited {
+                    Err(vec![self.eof_err()])
+                } else {
+                    Ok((open_spacing, TokenStream::new(buf)))
+                };
+            } else {
+                // Get the next normal token.
+                let (this_tok, this_spacing) = self.bump();
+                buf.push(TokenTree::Token(this_tok, this_spacing));
             }
         }
     }
@@ -111,9 +106,9 @@ impl<'psess, 'src> Lexer<'psess, 'src> {
         let delim_span = DelimSpan::from_pair(pre_span, self.token.span);
         let sm = self.psess.source_map();
 
-        let close_spacing = match self.token.kind {
-            // Correct delimiter.
-            token::CloseDelim(close_delim) if close_delim == open_delim => {
+        let close_spacing = if let Some(close_delim) = self.token.kind.close_delim() {
+            if close_delim == open_delim {
+                // Correct delimiter.
                 let (open_brace, open_brace_span) = self.diag_info.open_braces.pop().unwrap();
                 let close_brace_span = self.token.span;
 
@@ -134,9 +129,8 @@ impl<'psess, 'src> Lexer<'psess, 'src> {
 
                 // Move past the closing delimiter.
                 self.bump_minimal()
-            }
-            // Incorrect delimiter.
-            token::CloseDelim(close_delim) => {
+            } else {
+                // Incorrect delimiter.
                 let mut unclosed_delimiter = None;
                 let mut candidate = None;
 
@@ -182,14 +176,13 @@ impl<'psess, 'src> Lexer<'psess, 'src> {
                     Spacing::Alone
                 }
             }
-            token::Eof => {
-                // Silently recover, the EOF token will be seen again
-                // and an error emitted then. Thus we don't pop from
-                // self.open_braces here. The choice of spacing value here
-                // doesn't matter.
-                Spacing::Alone
-            }
-            _ => unreachable!(),
+        } else {
+            assert_eq!(self.token.kind, token::Eof);
+            // Silently recover, the EOF token will be seen again
+            // and an error emitted then. Thus we don't pop from
+            // self.open_braces here. The choice of spacing value here
+            // doesn't matter.
+            Spacing::Alone
         };
 
         let spacing = DelimSpacing::new(open_spacing, close_spacing);
diff --git a/compiler/rustc_parse/src/lexer/unicode_chars.rs b/compiler/rustc_parse/src/lexer/unicode_chars.rs
index 2bfa1ea4e05..751d13af433 100644
--- a/compiler/rustc_parse/src/lexer/unicode_chars.rs
+++ b/compiler/rustc_parse/src/lexer/unicode_chars.rs
@@ -5,7 +5,7 @@ use rustc_span::{BytePos, Pos, Span, kw};
 
 use super::Lexer;
 use crate::errors::TokenSubstitution;
-use crate::token::{self, Delimiter};
+use crate::token;
 
 #[rustfmt::skip] // for line breaks
 pub(super) static UNICODE_ARRAY: &[(char, &str, &str)] = &[
@@ -315,12 +315,12 @@ const ASCII_ARRAY: &[(&str, &str, Option<token::TokenKind>)] = &[
     ("!", "Exclamation Mark", Some(token::Bang)),
     ("?", "Question Mark", Some(token::Question)),
     (".", "Period", Some(token::Dot)),
-    ("(", "Left Parenthesis", Some(token::OpenDelim(Delimiter::Parenthesis))),
-    (")", "Right Parenthesis", Some(token::CloseDelim(Delimiter::Parenthesis))),
-    ("[", "Left Square Bracket", Some(token::OpenDelim(Delimiter::Bracket))),
-    ("]", "Right Square Bracket", Some(token::CloseDelim(Delimiter::Bracket))),
-    ("{", "Left Curly Brace", Some(token::OpenDelim(Delimiter::Brace))),
-    ("}", "Right Curly Brace", Some(token::CloseDelim(Delimiter::Brace))),
+    ("(", "Left Parenthesis", Some(token::OpenParen)),
+    (")", "Right Parenthesis", Some(token::CloseParen)),
+    ("[", "Left Square Bracket", Some(token::OpenBracket)),
+    ("]", "Right Square Bracket", Some(token::CloseBracket)),
+    ("{", "Left Curly Brace", Some(token::OpenBrace)),
+    ("}", "Right Curly Brace", Some(token::CloseBrace)),
     ("*", "Asterisk", Some(token::Star)),
     ("/", "Slash", Some(token::Slash)),
     ("\\", "Backslash", None),