Remove TokenStream::from_streams.

By inlining it into the only non-test call site. The one test call site
is changed to use `TokenStreamBuilder`.

Author: nnethercote

compiler/rustc_ast/src/tokenstream.rs

@@ -399,45 +399,6 @@ impl TokenStream {
         self.0.len()
     }
 
-    pub fn from_streams(mut streams: SmallVec<[TokenStream; 2]>) -> TokenStream {
-        match streams.len() {
-            0 => TokenStream::default(),
-            1 => streams.pop().unwrap(),
-            _ => {
-                // We are going to extend the first stream in `streams` with
-                // the elements from the subsequent streams. This requires
-                // using `make_mut()` on the first stream, and in practice this
-                // doesn't cause cloning 99.9% of the time.
-                //
-                // One very common use case is when `streams` has two elements,
-                // where the first stream has any number of elements within
-                // (often 1, but sometimes many more) and the second stream has
-                // a single element within.
-
-                // Determine how much the first stream will be extended.
-                // Needed to avoid quadratic blow up from on-the-fly
-                // reallocations (#57735).
-                let num_appends = streams.iter().skip(1).map(|ts| ts.len()).sum();
-
-                // Get the first stream. If it's `None`, create an empty
-                // stream.
-                let mut iter = streams.drain(..);
-                let mut first_stream_lrc = iter.next().unwrap().0;
-
-                // Append the elements to the first stream, after reserving
-                // space for them.
-                let first_vec_mut = Lrc::make_mut(&mut first_stream_lrc);
-                first_vec_mut.reserve(num_appends);
-                for stream in iter {
-                    first_vec_mut.extend(stream.0.iter().cloned());
-                }
-
-                // Create the final `TokenStream`.
-                TokenStream(first_stream_lrc)
-            }
-        }
-    }
-
     pub fn trees(&self) -> CursorRef<'_> {
         CursorRef::new(self)
     }
@@ -605,7 +566,43 @@ impl TokenStreamBuilder {
     }
 
     pub fn build(self) -> TokenStream {
-        TokenStream::from_streams(self.0)
+        let mut streams = self.0;
+        match streams.len() {
+            0 => TokenStream::default(),
+            1 => streams.pop().unwrap(),
+            _ => {
+                // We are going to extend the first stream in `streams` with
+                // the elements from the subsequent streams. This requires
+                // using `make_mut()` on the first stream, and in practice this
+                // doesn't cause cloning 99.9% of the time.
+                //
+                // One very common use case is when `streams` has two elements,
+                // where the first stream has any number of elements within
+                // (often 1, but sometimes many more) and the second stream has
+                // a single element within.
+
+                // Determine how much the first stream will be extended.
+                // Needed to avoid quadratic blow up from on-the-fly
+                // reallocations (#57735).
+                let num_appends = streams.iter().skip(1).map(|ts| ts.len()).sum();
+
+                // Get the first stream. If it's `None`, create an empty
+                // stream.
+                let mut iter = streams.drain(..);
+                let mut first_stream_lrc = iter.next().unwrap().0;
+
+                // Append the elements to the first stream, after reserving
+                // space for them.
+                let first_vec_mut = Lrc::make_mut(&mut first_stream_lrc);
+                first_vec_mut.reserve(num_appends);
+                for stream in iter {
+                    first_vec_mut.extend(stream.0.iter().cloned());
+                }
+
+                // Create the final `TokenStream`.
+                TokenStream(first_stream_lrc)
+            }
+        }
     }
 }
 

compiler/rustc_expand/src/tokenstream/tests.rs

@@ -4,7 +4,6 @@ use rustc_ast::token;
 use rustc_ast::tokenstream::{Spacing, TokenStream, TokenStreamBuilder, TokenTree};
 use rustc_span::create_default_session_globals_then;
 use rustc_span::{BytePos, Span, Symbol};
-use smallvec::smallvec;
 
 fn string_to_ts(string: &str) -> TokenStream {
     string_to_stream(string.to_owned())
@@ -24,7 +23,10 @@ fn test_concat() {
         let test_res = string_to_ts("foo::bar::baz");
         let test_fst = string_to_ts("foo::bar");
         let test_snd = string_to_ts("::baz");
-        let eq_res = TokenStream::from_streams(smallvec![test_fst, test_snd]);
+        let mut builder = TokenStreamBuilder::new();
+        builder.push(test_fst);
+        builder.push(test_snd);
+        let eq_res = builder.build();
         assert_eq!(test_res.trees().count(), 5);
         assert_eq!(eq_res.trees().count(), 5);
         assert_eq!(test_res.eq_unspanned(&eq_res), true);