From 23d1bfb4111d8aff513659f2b3e3dd695b9b6e03 Mon Sep 17 00:00:00 2001
From: Martin Odersky <odersky@gmail.com>
Date: Mon, 22 Aug 2016 15:46:06 +0200
Subject: Make expressions using GADTs type check in later phases

GADT logic is lost after PatMat. To make code typecheck, the typer
should already insert casts where a subtype check succeeded because
it involved bounds established by a GADT comparison.
---
 src/dotty/tools/dotc/typer/Typer.scala | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

(limited to 'src/dotty/tools/dotc/typer/Typer.scala')

diff --git a/src/dotty/tools/dotc/typer/Typer.scala b/src/dotty/tools/dotc/typer/Typer.scala
index 7eb022b51..39d9d267e 100644
--- a/src/dotty/tools/dotc/typer/Typer.scala
+++ b/src/dotty/tools/dotc/typer/Typer.scala
@@ -1715,6 +1715,7 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
         else
           missingArgs
       case _ =>
+        ctx.typeComparer.GADTused = false
         if (ctx.mode is Mode.Pattern) {
           tree match {
             case _: RefTree | _: Literal if !isVarPattern(tree) =>
@@ -1723,7 +1724,9 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
           }
           tree
         }
-        else if (tree.tpe <:< pt) tree
+        else if (tree.tpe <:< pt)
+          if (ctx.typeComparer.GADTused) tree.asInstance(pt)
+          else tree
         else if (wtp.isInstanceOf[MethodType]) missingArgs
         else {
           typr.println(i"adapt to subtype ${tree.tpe} !<:< $pt")
-- 
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