From 6e5dcab53a926cfaff7bc613ccee8669de96dc56 Mon Sep 17 00:00:00 2001
From: odersky <odersky@gmail.com>
Date: Tue, 2 Jul 2024 14:30:05 +0200
Subject: [PATCH] Streamline isConcrete a bit more

---
 .../src/dotty/tools/dotc/core/MatchTypes.scala   | 16 ++--------------
 compiler/src/dotty/tools/dotc/core/Types.scala   |  1 +
 2 files changed, 3 insertions(+), 14 deletions(-)

diff --git a/compiler/src/dotty/tools/dotc/core/MatchTypes.scala b/compiler/src/dotty/tools/dotc/core/MatchTypes.scala
index 61caceccd5d4..a3becea40886 100644
--- a/compiler/src/dotty/tools/dotc/core/MatchTypes.scala
+++ b/compiler/src/dotty/tools/dotc/core/MatchTypes.scala
@@ -34,24 +34,12 @@ object MatchTypes:
         true
       case tp1: TermRef =>
         !tp1.symbol.is(Param) && isConcrete(tp1.underlying)
-      case tp1: TermParamRef =>
+      case _: (ParamRef | MatchType) =>
         false
-      case tp1: SingletonType =>
-        isConcrete(tp1.underlying)
-      case tp1: ExprType =>
-        isConcrete(tp1.underlying)
-      case tp1: AnnotatedType =>
-        isConcrete(tp1.parent)
-      case tp1: RefinedOrRecType =>
+      case tp1: TypeProxy =>
         isConcrete(tp1.underlying)
       case tp1: AndOrType =>
         isConcrete(tp1.tp1) && isConcrete(tp1.tp2)
-      case tp1: TypeVar =>
-        isConcrete(tp1.underlying)
-      case tp1: LazyRef =>
-        isConcrete(tp1.ref)
-      case tp1: FlexibleType =>
-        isConcrete(tp1.hi)
       case _ =>
         false
   end isConcrete
diff --git a/compiler/src/dotty/tools/dotc/core/Types.scala b/compiler/src/dotty/tools/dotc/core/Types.scala
index 6d84242648b2..f9588c5b97f5 100644
--- a/compiler/src/dotty/tools/dotc/core/Types.scala
+++ b/compiler/src/dotty/tools/dotc/core/Types.scala
@@ -76,6 +76,7 @@ object Types extends TypeUtils {
    *        |              +- HKTypeLambda
    *        |              +- MatchType
    *        |              +- FlexibleType
+   *        |              +- LazyRef
    *        |
    *        +- GroundType -+- AndType
    *                       +- OrType