Fix scala#10573: Devirtualize member selection when matching

Author: nicolasstucki

compiler/src/scala/quoted/runtime/impl/Matcher.scala

@@ -231,7 +231,7 @@ object Matcher {
             scrutinee =?= expr2
 
           /* Match selection */
-          case (ref: Ref, Select(qual2, _)) if symbolMatch(scrutinee.symbol, pattern.symbol) =>
+          case (ref: Ref, Select(qual2, _)) if symbolMatch(scrutinee, pattern) =>
             ref match
               case Select(qual1, _) => qual1 =?= qual2
               case ref: Ident =>
@@ -240,7 +240,7 @@ object Matcher {
                   case _ => matched
 
           /* Match reference */
-          case (_: Ref, _: Ident) if symbolMatch(scrutinee.symbol, pattern.symbol) =>
+          case (_: Ref, _: Ident) if symbolMatch(scrutinee, pattern) =>
             matched
 
           /* Match application */
@@ -348,10 +348,21 @@ object Matcher {
      *   - The scrutinee has is in the environment and they are equivalent
      *   - The scrutinee overrides the symbol of the pattern
      */
-    private def symbolMatch(scrutinee: Symbol, pattern: Symbol)(using Env): Boolean =
-      scrutinee == pattern
-      || summon[Env].get(scrutinee).contains(pattern)
-      || scrutinee.allOverriddenSymbols.contains(pattern)
+    private def symbolMatch(scrutineeTree: Tree, patternTree: Tree)(using Env): Boolean =
+      val scrutinee = scrutineeTree.symbol
+      val devirtualizedScrutinee = scrutineeTree match
+        case Select(qual, _) =>
+          // TODO improve performance
+          qual.tpe.typeSymbol.methods.find( sym =>
+            sym.name == scrutinee.name &&
+            sym.allOverriddenSymbols.contains(scrutinee)
+          ).getOrElse(scrutinee)
+        case _ => scrutinee
+      val pattern = patternTree.symbol
+
+      devirtualizedScrutinee == pattern
+      || summon[Env].get(devirtualizedScrutinee).contains(pattern)
+      || devirtualizedScrutinee.allOverriddenSymbols.contains(pattern)
 
     private object ClosedPatternTerm {
       /** Matches a term that does not contain free variables defined in the pattern (i.e. not defined in `Env`) */

tests/pos-macros/i10573/Macro_1.scala

@@ -0,0 +1,16 @@
+import scala.quoted._
+
+
+trait A { def foo: Int }
+class B extends A { def foo: Int = 1 }
+
+inline def test(): Unit = ${ testExpr() }
+
+def testExpr()(using Quotes): Expr[Unit] = {
+  val e0: Expr[A] = '{ new B }
+  val e1: Expr[Int] = '{ $e0.foo }
+  e1 match
+    case '{ ($x: B).foo } => '{ val b: B = $x; () }
+    case _ => quotes.reflect.report.throwError("did not match")
+}
+

tests/pos-macros/i10573/Test_2.scala

@@ -0,0 +1,2 @@
+
+def Test = test()