diff options
Diffstat (limited to 'compiler/rustc_parse/src/parser/attr_wrapper.rs')
| -rw-r--r-- | compiler/rustc_parse/src/parser/attr_wrapper.rs | 31 |
1 files changed, 16 insertions, 15 deletions
diff --git a/compiler/rustc_parse/src/parser/attr_wrapper.rs b/compiler/rustc_parse/src/parser/attr_wrapper.rs index 67d2424bb48..e90568f177c 100644 --- a/compiler/rustc_parse/src/parser/attr_wrapper.rs +++ b/compiler/rustc_parse/src/parser/attr_wrapper.rs @@ -295,21 +295,22 @@ impl<'a> Parser<'a> { let num_calls = end_pos - start_pos; - // If we have no attributes, then we will never need to - // use any replace ranges. - let replace_ranges: Box<[ReplaceRange]> = if ret.attrs().is_empty() && !self.capture_cfg { - Box::new([]) - } else { - // Grab any replace ranges that occur *inside* the current AST node. - // We will perform the actual replacement when we convert the `LazyAttrTokenStream` - // to an `AttrTokenStream`. - self.capture_state.replace_ranges[replace_ranges_start..replace_ranges_end] - .iter() - .cloned() - .chain(inner_attr_replace_ranges.iter().cloned()) - .map(|(range, data)| ((range.start - start_pos)..(range.end - start_pos), data)) - .collect() - }; + // This is hot enough for `deep-vector` that checking the conditions for an empty iterator + // is measurably faster than actually executing the iterator. + let replace_ranges: Box<[ReplaceRange]> = + if replace_ranges_start == replace_ranges_end && inner_attr_replace_ranges.is_empty() { + Box::new([]) + } else { + // Grab any replace ranges that occur *inside* the current AST node. + // We will perform the actual replacement when we convert the `LazyAttrTokenStream` + // to an `AttrTokenStream`. + self.capture_state.replace_ranges[replace_ranges_start..replace_ranges_end] + .iter() + .cloned() + .chain(inner_attr_replace_ranges.iter().cloned()) + .map(|(range, data)| ((range.start - start_pos)..(range.end - start_pos), data)) + .collect() + }; let tokens = LazyAttrTokenStream::new(LazyAttrTokenStreamImpl { start_token, |