Handle comparing with TypeVar in mergeRefinedOrApplied

DolphinChips · tgodzik · commit c88073557a03 · 2025-05-12T12:17:51.000+02:00
Closes scala#23032 [Cherry-picked 9b060ec]
diff --git a/compiler/src/dotty/tools/dotc/core/TypeOps.scala b/compiler/src/dotty/tools/dotc/core/TypeOps.scala
@@ -284,7 +284,15 @@ object TypeOps:
           }
         case AndType(tp11, tp12) =>
           mergeRefinedOrApplied(tp11, tp2) & mergeRefinedOrApplied(tp12, tp2)
-        case tp1: TypeParamRef if tp1 == tp2 => tp1
+        case tp1: TypeParamRef =>
+          tp2.stripTypeVar match
+            case tp2: TypeParamRef if tp1 == tp2 => tp1
+            case _ => fail
+        case tp1: TypeVar =>
+          tp2 match
+            case tp2: TypeVar if tp1 == tp2 => tp1
+            case tp2: TypeParamRef if tp1.stripTypeVar == tp2 => tp2
+            case _ => fail
         case _ => fail
       }
     }
diff --git a/tests/pos/i23032.scala b/tests/pos/i23032.scala
@@ -0,0 +1,2 @@
+def f[F[_], T, U]: F[T] | F[U] = ???
+def x = f.toString

Original file line number	Diff line number	Diff line change
`@@ -284,7 +284,15 @@ object TypeOps:`
`284`	`284`	`}`
`285`	`285`	`case AndType(tp11, tp12) =>`
`286`	`286`	`mergeRefinedOrApplied(tp11, tp2) & mergeRefinedOrApplied(tp12, tp2)`
`287`		`- case tp1: TypeParamRef if tp1 == tp2 => tp1`
	`287`	`+ case tp1: TypeParamRef =>`
	`288`	`+ tp2.stripTypeVar match`
	`289`	`+ case tp2: TypeParamRef if tp1 == tp2 => tp1`
	`290`	`+ case _ => fail`
	`291`	`+ case tp1: TypeVar =>`
	`292`	`+ tp2 match`
	`293`	`+ case tp2: TypeVar if tp1 == tp2 => tp1`
	`294`	`+ case tp2: TypeParamRef if tp1.stripTypeVar == tp2 => tp2`
	`295`	`+ case _ => fail`
`288`	`296`	`case _ => fail`
`289`	`297`	`}`
`290`	`298`	`}`