Special case quote!/quote_spanned! for 1 and 2 tts.

These make crates that use `quote` compile faster. I also tried specializing for 3 tts, but the rules are more complex and the additional perf wins are much smaller than they are for 1 and 2 tts.
dtolnay · Apr 11, 2022 · 9a2530a · 9a2530a
1 parent 31c3be4
commit 9a2530a
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Showing 3 changed files with 48 additions and 11 deletions.
diff --git a/src/lib.rs b/src/lib.rs
@@ -473,6 +473,28 @@ macro_rules! quote {
     () => {
         $crate::__private::TokenStream::new()
     };
+
+    // Special case rule for a single tt, for performance.
+    ($tt:tt) => {{
+        let mut _s = $crate::__private::TokenStream::new();
+        $crate::quote_token!($tt _s);
+        _s
+    }};
+
+    // Special case rules for two tts, for performance.
+    (# $var:ident) => {{
+        let mut _s = $crate::__private::TokenStream::new();
+        $crate::ToTokens::to_tokens(&$var, &mut _s);
+        _s
+    }};
+    ($tt1:tt $tt2:tt) => {{
+        let mut _s = $crate::__private::TokenStream::new();
+        $crate::quote_token!($tt1 _s);
+        $crate::quote_token!($tt2 _s);
+        _s
+    }};
+
+    // Catch-all rule for all remaining inputs.
     ($($tt:tt)*) => {{
         let mut _s = $crate::__private::TokenStream::new();
         $crate::quote_each_token!(_s $($tt)*);
@@ -582,6 +604,31 @@ macro_rules! quote_spanned {
         let _: $crate::__private::Span = $span;
         $crate::__private::TokenStream::new()
     }};
+
+    // Special case rule for a single tt, for performance.
+    ($span:expr=> $tt:tt) => {{
+        let mut _s = $crate::__private::TokenStream::new();
+        let _span: $crate::__private::Span = $span;
+        $crate::quote_token_spanned!($tt _s _span);
+        _s
+    }};
+
+    // Special case rules for two tts, for performance.
+    ($span:expr=> # $var:ident) => {{
+        let mut _s = $crate::__private::TokenStream::new();
+        let _span: $crate::__private::Span = $span;
+        $crate::ToTokens::to_tokens(&$var, &mut _s);
+        _s
+    }};
+    ($span:expr=> $tt1:tt $tt2:tt) => {{
+        let mut _s = $crate::__private::TokenStream::new();
+        let _span: $crate::__private::Span = $span;
+        $crate::quote_token_spanned!($tt1 _s _span);
+        $crate::quote_token_spanned!($tt2 _s _span);
+        _s
+    }};
+
+    // Catch-all rule for all remaining inputs.
     ($span:expr=> $($tt:tt)*) => {{
         let mut _s = $crate::__private::TokenStream::new();
         let _span: $crate::__private::Span = $span;

diff --git a/tests/ui/not-quotable.stderr b/tests/ui/not-quotable.stderr
@@ -14,4 +14,4 @@ error[E0277]: the trait bound `Ipv4Addr: ToTokens` is not satisfied
             RepInterp<T>
             String
           and 23 others
-  = note: this error originates in the macro `$crate::quote_token_with_context` (in Nightly builds, run with -Z macro-backtrace for more info)
+  = note: this error originates in the macro `quote` (in Nightly builds, run with -Z macro-backtrace for more info)
diff --git a/tests/ui/not-repeatable.stderr b/tests/ui/not-repeatable.stderr
@@ -23,16 +23,6 @@ error[E0599]: the method `quote_into_iter` exists for struct `Ipv4Addr`, but its
              `&mut Ipv4Addr: Iterator`
              which is required by `&mut Ipv4Addr: quote::__private::ext::RepIteratorExt`
 note: the following traits must be implemented
-    --> $RUST/core/src/iter/traits/iterator.rs
-     |
-     | /  pub trait Iterator {
-     | |      /// The type of the elements being iterated over.
-     | |      #[stable(feature = "rust1", since = "1.0.0")]
-     | |      type Item;
-...    |
-     | |      }
-     | |  }
-     | |__^
      |
     ::: src/to_tokens.rs
      |