Auto merge of #122718 - workingjubilee:eyeliner-for-contrast, r=lcnr

Inline a bunch of trivial conditions in parser

It is often the case that these small, conditional functions, when inlined, reveal notable optimization opportunities to LLVM. While saethlin has done a lot of good work on making these kinds of small functions not need `#[inline]` tags as much, being clearer about what we want inlined will get both the MIR opts and LLVM to pursue it more aggressively.

On local perf runs, this seems fruitful. Let's see what rust-timer says.

r? `@ghost`

compiler/rustc_parse/src/parser/mod.rs

@@ -449,6 +449,7 @@ impl<'a> Parser<'a> {
         parser
     }
 
+    #[inline]
     pub fn recovery(mut self, recovery: Recovery) -> Self {
         self.recovery = recovery;
         self
@@ -461,6 +462,7 @@ impl<'a> Parser<'a> {
     ///
     /// Technically, this only needs to restrict eager recovery by doing lookahead at more tokens.
     /// But making the distinction is very subtle, and simply forbidding all recovery is a lot simpler to uphold.
+    #[inline]
     fn may_recover(&self) -> bool {
         matches!(self.recovery, Recovery::Allowed)
     }
@@ -548,6 +550,7 @@ impl<'a> Parser<'a> {
     ///
     /// This method will automatically add `tok` to `expected_tokens` if `tok` is not
     /// encountered.
+    #[inline]
     fn check(&mut self, tok: &TokenKind) -> bool {
         let is_present = self.token == *tok;
         if !is_present {
@@ -556,6 +559,7 @@ impl<'a> Parser<'a> {
         is_present
     }
 
+    #[inline]
     fn check_noexpect(&self, tok: &TokenKind) -> bool {
         self.token == *tok
     }
@@ -564,6 +568,7 @@ impl<'a> Parser<'a> {
     ///
     /// the main purpose of this function is to reduce the cluttering of the suggestions list
     /// which using the normal eat method could introduce in some cases.
+    #[inline]
     pub fn eat_noexpect(&mut self, tok: &TokenKind) -> bool {
         let is_present = self.check_noexpect(tok);
         if is_present {
@@ -573,6 +578,7 @@ impl<'a> Parser<'a> {
     }
 
     /// Consumes a token 'tok' if it exists. Returns whether the given token was present.
+    #[inline]
     pub fn eat(&mut self, tok: &TokenKind) -> bool {
         let is_present = self.check(tok);
         if is_present {
@@ -583,11 +589,13 @@ impl<'a> Parser<'a> {
 
     /// If the next token is the given keyword, returns `true` without eating it.
     /// An expectation is also added for diagnostics purposes.
+    #[inline]
     fn check_keyword(&mut self, kw: Symbol) -> bool {
         self.expected_tokens.push(TokenType::Keyword(kw));
         self.token.is_keyword(kw)
     }
 
+    #[inline]
     fn check_keyword_case(&mut self, kw: Symbol, case: Case) -> bool {
         if self.check_keyword(kw) {
             return true;
@@ -606,6 +614,7 @@ impl<'a> Parser<'a> {
     /// If the next token is the given keyword, eats it and returns `true`.
     /// Otherwise, returns `false`. An expectation is also added for diagnostics purposes.
     // Public for rustfmt usage.
+    #[inline]
     pub fn eat_keyword(&mut self, kw: Symbol) -> bool {
         if self.check_keyword(kw) {
             self.bump();
@@ -618,6 +627,7 @@ impl<'a> Parser<'a> {
     /// Eats a keyword, optionally ignoring the case.
     /// If the case differs (and is ignored) an error is issued.
     /// This is useful for recovery.
+    #[inline]
     fn eat_keyword_case(&mut self, kw: Symbol, case: Case) -> bool {
         if self.eat_keyword(kw) {
             return true;
@@ -635,6 +645,7 @@ impl<'a> Parser<'a> {
         false
     }
 
+    #[inline]
     fn eat_keyword_noexpect(&mut self, kw: Symbol) -> bool {
         if self.token.is_keyword(kw) {
             self.bump();
@@ -656,6 +667,7 @@ impl<'a> Parser<'a> {
         self.token.is_keyword(kw) && self.look_ahead(1, |t| t.is_ident() && !t.is_reserved_ident())
     }
 
+    #[inline]
     fn check_or_expected(&mut self, ok: bool, typ: TokenType) -> bool {
         if ok {
             true
@@ -703,6 +715,7 @@ impl<'a> Parser<'a> {
 
     /// Checks to see if the next token is either `+` or `+=`.
     /// Otherwise returns `false`.
+    #[inline]
     fn check_plus(&mut self) -> bool {
         self.check_or_expected(
             self.token.is_like_plus(),