Changes to how we compute type parameters

Aim: Avoid expensive scanning of definitions in denotations other than the initial one.

Technique:

1. If phase is erased, type params is Nil (except for Array class)
2. Otherwise, type params is the same as it was in initial phase.

1 files changed, 6 insertions, 2 deletions

diff --git a/src/dotty/tools/dotc/core/SymDenotations.scala b/src/dotty/tools/dotc/core/SymDenotations.scala
index 362738caf..248cf3de3 100644
--- a/src/dotty/tools/dotc/core/SymDenotations.scala
+++ b/src/dotty/tools/dotc/core/SymDenotations.scala
@@ -805,8 +805,12 @@ object SymDenotations {
 
     /** The type parameters of this class */
     override final def typeParams(implicit ctx: Context): List[TypeSymbol] = {
-      def computeTypeParams = decls.filter(sym =>
-        (sym is TypeParam) && sym.owner == symbol).asInstanceOf[List[TypeSymbol]]
+      def computeTypeParams = {
+        if (ctx.phase.erasedTypes && (this ne defn.ArrayClass)) Nil
+        else if (this ne initial) initial.asSymDenotation.typeParams
+        else decls.filter(sym =>
+          (sym is TypeParam) && sym.owner == symbol).asInstanceOf[List[TypeSymbol]]
+      }
       if (myTypeParams == null) myTypeParams = computeTypeParams
       myTypeParams
     }