Merge pull request #7583 from dotty-staging/fix-#7580

Fix #7580: Desugar TupleXXL selection into `apply(n)`

Author: bishabosha

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

@@ -1098,7 +1098,10 @@ object desugar {
           val firstDef =
             ValDef(tmpName, TypeTree(), matchExpr)
               .withSpan(pat.span.union(rhs.span)).withMods(patMods)
-          def selector(n: Int) = Select(Ident(tmpName), nme.selectorName(n))
+          val useSelectors = vars.length <= 22
+          def selector(n: Int) =
+            if useSelectors then Select(Ident(tmpName), nme.selectorName(n))
+            else Apply(Select(Ident(tmpName), nme.apply), Literal(Constant(n)) :: Nil)
           val restDefs =
             for (((named, tpt), n) <- vars.zipWithIndex if named.name != nme.WILDCARD)
             yield

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

@@ -28,6 +28,7 @@ i5720.scala
 
 # Tuples
 toexproftuple.scala
+i7580.scala
 
 # Nullability
 nullable.scala

tests/pos/i7580.scala

@@ -0,0 +1,5 @@
+
+def foo =
+  val List(a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14, a15, a16, a17, a18, a19, a20, a21, a22, a23, _:_*) = List.fill(25)(0)
+
+  ()