Always assume two TypeTest[S, T].unapply are the same

liufengyun · liufengyun · commit 42697808888b · 2021-04-12T14:26:14.000+02:00
if they are equivalent in types.
diff --git a/compiler/src/dotty/tools/dotc/transform/patmat/Space.scala b/compiler/src/dotty/tools/dotc/transform/patmat/Space.scala
@@ -521,7 +521,9 @@ class SpaceEngine(using Context) extends SpaceLogic {
   }
 
   def isSameUnapply(tp1: TermRef, tp2: TermRef): Boolean =
-    tp1.prefix.isStable && tp2.prefix.isStable && tp1 =:= tp2
+    // always assume two TypeTest[S, T].unapply are the same if they are equal in types
+    (tp1.prefix.isStable && tp2.prefix.isStable || tp1.symbol == defn.TypeTest_unapply)
+    && tp1 =:= tp2
 
   /** Parameter types of the case class type `tp`. Adapted from `unapplyPlan` in patternMatcher  */
   def signature(unapp: TermRef, scrutineeTp: Type, argLen: Int): List[Type] = {
diff --git a/tests/patmat/i12020.check b/tests/patmat/i12020.check
@@ -0,0 +1 @@
+19: Pattern Match Exhaustivity: _: TypeDef

Original file line number	Diff line number	Diff line change
`@@ -521,7 +521,9 @@ class SpaceEngine(using Context) extends SpaceLogic {`
`521`	`521`	`}`
`522`	`522`
`523`	`523`	`def isSameUnapply(tp1: TermRef, tp2: TermRef): Boolean =`
`524`		`- tp1.prefix.isStable && tp2.prefix.isStable && tp1 =:= tp2`
	`524`	`+ // always assume two TypeTest[S, T].unapply are the same if they are equal in types`
	`525`	`+ (tp1.prefix.isStable && tp2.prefix.isStable \|\| tp1.symbol == defn.TypeTest_unapply)`
	`526`	`+ && tp1 =:= tp2`
`525`	`527`
`526`	`528`	/** Parameter types of the case class type `tp`. Adapted from `unapplyPlan` in patternMatcher */
`527`	`529`	`def signature(unapp: TermRef, scrutineeTp: Type, argLen: Int): List[Type] = {`
Original file line number	Diff line number	Diff line change
`@@ -0,0 +1 @@`
	`1`	`+19: Pattern Match Exhaustivity: _: TypeDef`