From 35975432852a7b67ca3dc6d34feaaf3797549ee1 Mon Sep 17 00:00:00 2001
From: SDSR <sdsr.sdsr@gmail.com>
Date: Tue, 26 Oct 2021 19:07:49 +0200
Subject: [PATCH] solves dotc assertion error on (non-sensical?) parameter
 type. #13769

---
 compiler/src/dotty/tools/dotc/parsing/Parsers.scala |  3 +++
 tests/neg/i13769.check                              | 10 ++++++++++
 tests/neg/i13769.scala                              |  2 ++
 3 files changed, 15 insertions(+)
 create mode 100644 tests/neg/i13769.check
 create mode 100644 tests/neg/i13769.scala

diff --git a/compiler/src/dotty/tools/dotc/parsing/Parsers.scala b/compiler/src/dotty/tools/dotc/parsing/Parsers.scala
index 44e7145d2ee1..aff7218e662b 100644
--- a/compiler/src/dotty/tools/dotc/parsing/Parsers.scala
+++ b/compiler/src/dotty/tools/dotc/parsing/Parsers.scala
@@ -442,6 +442,9 @@ object Parsers {
     def convertToParam(tree: Tree, mods: Modifiers, expected: String = "formal parameter"): ValDef = tree match {
       case id @ Ident(name) =>
         makeParameter(name.asTermName, TypeTree(), mods, isBackquoted = isBackquoted(id)).withSpan(tree.span)
+      case Typed(_, tpt: TypeBoundsTree) =>
+        syntaxError(s"not a legal $expected", tree.span)
+        makeParameter(nme.ERROR, tree, mods)
       case Typed(id @ Ident(name), tpt) =>
         makeParameter(name.asTermName, tpt, mods, isBackquoted = isBackquoted(id)).withSpan(tree.span)
       case Typed(Splice(Ident(name)), tpt) =>
diff --git a/tests/neg/i13769.check b/tests/neg/i13769.check
new file mode 100644
index 000000000000..7785fbf4d198
--- /dev/null
+++ b/tests/neg/i13769.check
@@ -0,0 +1,10 @@
+-- Error: tests/neg/i13769.scala:2:18 ----------------------------------------------------------------------------------
+2 |val te = tup.map((x: _ <: Int) => List(x)) // error // error
+  |                  ^^^^^^^^^^^
+  |                  not a legal formal parameter
+-- [E006] Not Found Error: tests/neg/i13769.scala:2:39 -----------------------------------------------------------------
+2 |val te = tup.map((x: _ <: Int) => List(x)) // error // error
+  |                                       ^
+  |                                       Not found: x
+
+longer explanation available when compiling with `-explain`
\ No newline at end of file
diff --git a/tests/neg/i13769.scala b/tests/neg/i13769.scala
new file mode 100644
index 000000000000..67575e821334
--- /dev/null
+++ b/tests/neg/i13769.scala
@@ -0,0 +1,2 @@
+val tup = (1, "s")
+val te = tup.map((x: _ <: Int) => List(x)) // error // error