Inline some hot lint pass functions.

These each have a single call site, due to being called from a
"combined" lint pass.

compiler/rustc_lint/src/builtin.rs

@@ -96,6 +96,7 @@ fn pierce_parens(mut expr: &ast::Expr) -> &ast::Expr {
 }
 
 impl EarlyLintPass for WhileTrue {
+    #[inline]
     fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
         if let ast::ExprKind::While(cond, _, label) = &e.kind
             && let cond = pierce_parens(cond)
@@ -360,6 +361,7 @@ impl EarlyLintPass for UnsafeCode {
         }
     }
 
+    #[inline]
     fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
         if let ast::ExprKind::Block(ref blk, _) = e.kind {
             // Don't warn about generated blocks; that'll just pollute the output.
@@ -582,6 +584,7 @@ impl MissingDoc {
 }
 
 impl<'tcx> LateLintPass<'tcx> for MissingDoc {
+    #[inline]
     fn enter_lint_attrs(&mut self, _cx: &LateContext<'_>, attrs: &[ast::Attribute]) {
         let doc_hidden = self.doc_hidden()
             || attrs.iter().any(|attr| {

compiler/rustc_lint/src/hidden_unicode_codepoints.rs

@@ -121,6 +121,7 @@ impl EarlyLintPass for HiddenUnicodeCodepoints {
         }
     }
 
+    #[inline]
     fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
         // byte strings are already handled well enough by `EscapeError::NonAsciiCharInByteString`
         match &expr.kind {

compiler/rustc_lint/src/unused.rs

@@ -946,6 +946,7 @@ impl UnusedParens {
 }
 
 impl EarlyLintPass for UnusedParens {
+    #[inline]
     fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
         match e.kind {
             ExprKind::Let(ref pat, _, _) | ExprKind::ForLoop(ref pat, ..) => {
@@ -1164,6 +1165,7 @@ impl EarlyLintPass for UnusedBraces {
         <Self as UnusedDelimLint>::check_stmt(self, cx, s)
     }
 
+    #[inline]
     fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
         <Self as UnusedDelimLint>::check_expr(self, cx, e);