PostTyper#normalizeTypeArgs: fast path to avoid allocations

smarter · smarter · commit 5ccec0201014 · 2018-01-30T16:19:24.000+01:00
According to -Yprofile-enabled, this reduces the amount of memory
allocated in PostTyper when compiling re2s from 39 MB to 26 MB
diff --git a/compiler/src/dotty/tools/dotc/transform/PostTyper.scala b/compiler/src/dotty/tools/dotc/transform/PostTyper.scala
@@ -150,7 +150,7 @@ class PostTyper extends MacroTransform with IdentityDenotTransformer { thisPhase
         }
         val (tycon, args) = decompose(tree)
         tycon.tpe.widen match {
-          case tp: PolyType =>
+          case tp: PolyType if args.exists(isNamedArg) =>
             val (namedArgs, otherArgs) = args.partition(isNamedArg)
             val args1 = reorderArgs(tp.paramNames, namedArgs.asInstanceOf[List[NamedArg]], otherArgs)
             TypeApply(tycon, args1).withPos(tree.pos).withType(tree.tpe)

Original file line number	Diff line number	Diff line change
`@@ -150,7 +150,7 @@ class PostTyper extends MacroTransform with IdentityDenotTransformer { thisPhase`
`150`	`150`	`}`
`151`	`151`	`val (tycon, args) = decompose(tree)`
`152`	`152`	`tycon.tpe.widen match {`
`153`		`- case tp: PolyType =>`
	`153`	`+ case tp: PolyType if args.exists(isNamedArg) =>`
`154`	`154`	`val (namedArgs, otherArgs) = args.partition(isNamedArg)`
`155`	`155`	`val args1 = reorderArgs(tp.paramNames, namedArgs.asInstanceOf[List[NamedArg]], otherArgs)`
`156`	`156`	`TypeApply(tycon, args1).withPos(tree.pos).withType(tree.tpe)`