Constrain patterns by both GADT upper bound & upcast

dwijnand · dwijnand · commit 5c5189e572f2 · 2022-06-07T11:03:59.000+01:00
diff --git a/compiler/src/dotty/tools/dotc/core/PatternTypeConstrainer.scala b/compiler/src/dotty/tools/dotc/core/PatternTypeConstrainer.scala
@@ -143,10 +143,10 @@ trait PatternTypeConstrainer { self: TypeComparer =>
               ctx.gadt.bounds(scrut.symbol) match {
                 case tb: TypeBounds =>
                   val hi = tb.hi
-                  constrainPatternType(pat, hi)
-                case null => false
+                  tryConstrainSimplePatternType(pat, hi)
+                case null => true
               }
-            case _ => false
+            case _ => true
           }
 
           def trySuperType =
@@ -159,7 +159,7 @@ trait PatternTypeConstrainer { self: TypeComparer =>
               tryConstrainSimplePatternType(pat, upcasted) || constrainUpcasted(upcasted)
             else true
 
-          tryGadtBounds || trySuperType
+          tryGadtBounds && trySuperType
       }
     }
 

Original file line number	Diff line number	Diff line change
`@@ -143,10 +143,10 @@ trait PatternTypeConstrainer { self: TypeComparer =>`
`143`	`143`	`ctx.gadt.bounds(scrut.symbol) match {`
`144`	`144`	`case tb: TypeBounds =>`
`145`	`145`	`val hi = tb.hi`
`146`		`- constrainPatternType(pat, hi)`
`147`		`- case null => false`
	`146`	`+ tryConstrainSimplePatternType(pat, hi)`
	`147`	`+ case null => true`
`148`	`148`	`}`
`149`		`- case _ => false`
	`149`	`+ case _ => true`
`150`	`150`	`}`
`151`	`151`
`152`	`152`	`def trySuperType =`
`@@ -159,7 +159,7 @@ trait PatternTypeConstrainer { self: TypeComparer =>`
`159`	`159`	`tryConstrainSimplePatternType(pat, upcasted) \|\| constrainUpcasted(upcasted)`
`160`	`160`	`else true`
`161`	`161`
`162`		`- tryGadtBounds \|\| trySuperType`
	`162`	`+ tryGadtBounds && trySuperType`
`163`	`163`	`}`
`164`	`164`	`}`
`165`	`165`