Precompute vector length in smart_resolve_path_fragment

bugadani · bugadani · commit 62f593bda9ef · 2020-12-20T21:38:41.000+01:00
diff --git a/compiler/rustc_resolve/src/late.rs b/compiler/rustc_resolve/src/late.rs
@@ -1891,8 +1891,9 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
                     self.r.trait_map.insert(id, traits);
                 }
 
-                let mut std_path = vec![Segment::from_ident(Ident::with_dummy_span(sym::std))];
+                let mut std_path = Vec::with_capacity(1 + path.len());
 
+                std_path.push(Segment::from_ident(Ident::with_dummy_span(sym::std)));
                 std_path.extend(path);
 
                 if self.r.primitive_type_table.primitive_types.contains_key(&path[0].ident.name) {

Original file line number	Diff line number	Diff line change
`@@ -1891,8 +1891,9 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {`
`1891`	`1891`	`self.r.trait_map.insert(id, traits);`
`1892`	`1892`	`}`
`1893`	`1893`
`1894`		`- let mut std_path = vec![Segment::from_ident(Ident::with_dummy_span(sym::std))];`
	`1894`	`+ let mut std_path = Vec::with_capacity(1 + path.len());`
`1895`	`1895`
	`1896`	`+ std_path.push(Segment::from_ident(Ident::with_dummy_span(sym::std)));`
`1896`	`1897`	`std_path.extend(path);`
`1897`	`1898`
`1898`	`1899`	`if self.r.primitive_type_table.primitive_types.contains_key(&path[0].ident.name) {`