Don't abbreviate tuple bindings if right-hand-side is named

We need to go through an explicit pattern match to drop the names.

Author: odersky

compiler/src/dotty/tools/dotc/ast/Desugar.scala

@@ -1254,8 +1254,9 @@ object desugar {
           pats.forall(isVarPattern)
         case _ => false
       }
+
       val isMatchingTuple: Tree => Boolean = {
-        case Tuple(es) => isTuplePattern(es.length)
+        case Tuple(es) => isTuplePattern(es.length) && !hasNamedArg(es)
         case _ => false
       }
 

tests/pos/named-tuples.check

@@ -0,0 +1,36 @@
+import annotation.experimental
+import language.experimental.namedTuples
+
+@main def Test =
+  locally:
+    val (x = x, y = y) = (x = 11, y = 22)
+    assert(x == 11 && y == 22)
+
+  locally:
+    val (x = a, y = b) = (x = 1, y = 2)
+    assert(a == 1 && b == 2)
+
+  locally:
+    val (x = a, y = b) = (x = 1, y = 2)
+    assert(a == 1 && b == 2)
+
+  locally:
+    val (x, y) = (x = 1, y = 2)
+    assert(x == 1 && y == 2)
+
+  locally:
+    val (a, b) = (x = 1, y = 2)
+    assert(a == 1 && b == 2)
+
+  (x = 1, y = 2) match
+    case (x = x, y = y) => assert(x == 1 && y == 2)
+
+  (x = 1, y = 2) match
+    case (x, y) => assert(x == 1 && y == 2)
+
+  (x = 1, y = 2) match
+    case (a, b) => assert(a == 1 && b == 2)
+
+
+
+