Normalize and dealias more when testing if TypeTests are unchecked

Tests #13433 with a classpath dependency

Author: EugeneFlesselle

compiler/src/dotty/tools/dotc/core/Types.scala

@@ -1534,6 +1534,12 @@ object Types extends TypeUtils {
       if (normed.exists) normed else this
     }
 
+    final def dealiasNormalized(using Context): Type =
+      val dealiased = dealias
+      dealiased.tryNormalize match
+        case NoType => dealiased
+        case normed => normed.dealiasNormalized
+
     /** If this type can be normalized at the top-level by rewriting match types
      *  of S[n] types, the result after applying all toplevel normalizations,
      *  otherwise NoType

compiler/src/dotty/tools/dotc/transform/TypeTestsCasts.scala

@@ -61,7 +61,7 @@ object TypeTestsCasts {
     extension (inline b: Boolean) inline def |||(inline s: String): String = if b then "" else s
 
     // Run just before ElimOpaque transform (which follows RefChecks)
-    def isAbstract(P: Type) = !P.dealias.typeSymbol.isClass
+    def isAbstract(P: Type) = !P.typeSymbol.isClass
 
     def replaceP(tp: Type)(using Context) = new TypeMap {
       def apply(tp: Type) = tp match {
@@ -133,10 +133,10 @@ object TypeTestsCasts {
     }
 
     def recur(X: Type, P: Type): String = trace(s"recur(${X.show}, ${P.show})") {
-      (X <:< P) ||| P.dealias.match
+      (X <:< P) ||| P.dealiasNormalized.match
       case _: SingletonType     => ""
-      case _: TypeProxy
-      if isAbstract(P)          => i"it refers to an abstract type member or type parameter"
+      case tp: TypeProxy
+      if isAbstract(tp)          => i"it refers to an abstract type member or type parameter"
       case defn.ArrayOf(tpT)    =>
         X match {
           case defn.ArrayOf(tpE)   => recur(tpE, tpT)

compiler/test/dotc/pos-test-pickling.blacklist

@@ -24,7 +24,7 @@ i16997.scala
 i7414.scala
 i17588.scala
 i9804.scala
-i13433.scala
+i13433a.scala
 i16649-irrefutable.scala
 strict-pattern-bindings-3.0-migration.scala
 i17186b.scala

tests/pos/i13433.scala renamed to tests/pos/i13433a.scala

@@ -2,7 +2,7 @@
 
 import scala.reflect.TypeTest
 
-type Matcher[A] = A match { case String => String }
+type Matcher[A] = A match { case String => A }
 
 def patternMatch[A](a: Any)(using tt: TypeTest[Any, Matcher[A]]): Option[Matcher[A]] = {
   // type T = RDF.Triple[Rdf]
@@ -20,6 +20,11 @@ def patternMatchWithAlias[A](a: Any)(using tt: TypeTest[Any, Matcher[A]]): Optio
   }
 }
 
+type S = String
+type MS = Matcher[S]
+
+type S2 = MS
+type MS2 = Matcher[S2]
 
 @main def main = {
   println(patternMatch[String]("abc"))
@@ -31,4 +36,13 @@ def patternMatchWithAlias[A](a: Any)(using tt: TypeTest[Any, Matcher[A]]): Optio
 
   println(patternMatch[String](1))
   println(patternMatchWithAlias[String](1))
+
+  println(patternMatch[String]("abc")(using (s: Any) => {
+    if s.isInstanceOf[S] then Some[s.type & Matcher[String]](s.asInstanceOf[s.type & Matcher[String]]) else None}))
+  println(patternMatch[String]("abc")(using (s: Any) => {
+    if s.isInstanceOf[MS] then Some[s.type & Matcher[String]](s.asInstanceOf[s.type & Matcher[String]]) else None}))
+  println(patternMatch[String]("abc")(using (s: Any) => {
+    if s.isInstanceOf[S2] then Some[s.type & Matcher[String]](s.asInstanceOf[s.type & Matcher[String]]) else None}))
+  println(patternMatch[String]("abc")(using (s: Any) => {
+    if s.isInstanceOf[MS2] then Some[s.type & Matcher[String]](s.asInstanceOf[s.type & Matcher[String]]) else None}))
 }

tests/pos/i13433c/A_1.scala

@@ -0,0 +1,25 @@
+import scala.reflect.TypeTest
+
+type Matcher[A] = A match { case String => A }
+
+def patternMatch[A](a: Any)(using tt: TypeTest[Any, Matcher[A]]): Option[Matcher[A]] = {
+  // type T = RDF.Triple[Rdf]
+  a match {
+    case res: Matcher[A] => Some(res)
+    case _ => None
+  }
+}
+
+def patternMatchWithAlias[A](a: Any)(using tt: TypeTest[Any, Matcher[A]]): Option[Matcher[A]] = {
+  type T = Matcher[A]
+  a match {
+    case res: T => Some(res)
+    case _ => None
+  }
+}
+
+type S = String
+type MS = Matcher[S]
+
+type S2 = MS
+type MS2 = Matcher[S2]

tests/pos/i13433c/B_2.scala

@@ -0,0 +1,22 @@
+//> using options -Xfatal-warnings -deprecation -feature
+
+@main def main = {
+  println(patternMatch[String]("abc"))
+  println(patternMatchWithAlias[String]("abc"))
+  println(patternMatch[String]("abc")(using (s: Any) => {
+    if s.isInstanceOf[Matcher[String]] then Some[s.type & Matcher[String]](s.asInstanceOf[s.type & Matcher[String]]) else None }))
+  println(patternMatchWithAlias[String]("abc")(using (s: Any) => {
+    if s.isInstanceOf[Matcher[String]] then Some[s.type & Matcher[String]](s.asInstanceOf[s.type & Matcher[String]]) else None }))
+
+  println(patternMatch[String](1))
+  println(patternMatchWithAlias[String](1))
+
+  println(patternMatch[String]("abc")(using (s: Any) => {
+    if s.isInstanceOf[S] then Some[s.type & Matcher[String]](s.asInstanceOf[s.type & Matcher[String]]) else None}))
+  println(patternMatch[String]("abc")(using (s: Any) => {
+    if s.isInstanceOf[MS] then Some[s.type & Matcher[String]](s.asInstanceOf[s.type & Matcher[String]]) else None}))
+  println(patternMatch[String]("abc")(using (s: Any) => {
+    if s.isInstanceOf[S2] then Some[s.type & Matcher[String]](s.asInstanceOf[s.type & Matcher[String]]) else None}))
+  println(patternMatch[String]("abc")(using (s: Any) => {
+    if s.isInstanceOf[MS2] then Some[s.type & Matcher[String]](s.asInstanceOf[s.type & Matcher[String]]) else None}))
+}