From 175dbd292ec1649be82e701f5eef0a5b8fa675a4 Mon Sep 17 00:00:00 2001
From: Quentin Bernet <quentin.bernet@epfl.ch>
Date: Thu, 20 Apr 2023 13:09:54 +0200
Subject: [PATCH 1/2] Add test for #12460

---
 tests/neg/i12460.scala | 7 +++++++
 1 file changed, 7 insertions(+)
 create mode 100644 tests/neg/i12460.scala

diff --git a/tests/neg/i12460.scala b/tests/neg/i12460.scala
new file mode 100644
index 000000000000..450bac7aa2d0
--- /dev/null
+++ b/tests/neg/i12460.scala
@@ -0,0 +1,7 @@
+
+extension (x: String = "123") // error
+  def f2 = x.reverse
+
+
+extension (x: => String) // error
+  def f2 = x.reverse

From b4c7a8b468687471ee9ec78a9581773f33ee9b1a Mon Sep 17 00:00:00 2001
From: Quentin Bernet <quentin.bernet@epfl.ch>
Date: Thu, 20 Apr 2023 13:13:33 +0200
Subject: [PATCH 2/2] Add WIP checkExtensionParameters

Does not compile !
---
 .../dotty/tools/dotc/typer/RefChecks.scala    | 24 +++++++++++++++++++
 tests/neg/i12460.scala                        |  4 ++--
 2 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/compiler/src/dotty/tools/dotc/typer/RefChecks.scala b/compiler/src/dotty/tools/dotc/typer/RefChecks.scala
index 4ca00ce6366f..d470b65bc1d8 100644
--- a/compiler/src/dotty/tools/dotc/typer/RefChecks.scala
+++ b/compiler/src/dotty/tools/dotc/typer/RefChecks.scala
@@ -1147,10 +1147,34 @@ class RefChecks extends MiniPhase { thisPhase =>
     tree
   }
 
+  // TODO: Refactor with the one in checkUnaryMethods
+  def checkExtensionParameters(sym: Symbol)(using Context): Unit =
+    if sym.is(Extension) || sym.name.is(ExtMethName) then
+      println(s"checkExtensionParameters: ${tpe.show}")
+      sym.info match
+        case tpe: MethodType =>
+          assert(tpe.paramNames.length == 1)
+          if tpe.isContextualMethod then checkExtensionParameters(tpe.resType)
+          else
+            val param: Type = tpe.paramInfos.head
+            val paramSymbol: Symbol = tpe.paramNames.head
+            // TODO: Add test of default argument here
+            param match
+              case ExprType(_) =>
+                report.error(em"$param is bad", paramSymbol.srcPos) // TODO: Find correct way to get position
+            
+            println(param.show)
+            println(param)
+            assert(true)
+            println("Done")
+        case tpe: PolyType =>
+          checkExtensionParameters(tpe.resType)
+
   override def transformDefDef(tree: DefDef)(using Context): DefDef = {
     checkNoPrivateOverrides(tree)
     checkImplicitNotFoundAnnotation.defDef(tree.symbol.denot)
     checkUnaryMethods(tree.symbol)
+    checkExtensionParameters(tree.symbol)
     tree
   }
 
diff --git a/tests/neg/i12460.scala b/tests/neg/i12460.scala
index 450bac7aa2d0..2f40f9107fef 100644
--- a/tests/neg/i12460.scala
+++ b/tests/neg/i12460.scala
@@ -1,7 +1,7 @@
-
+/*
 extension (x: String = "123") // error
   def f2 = x.reverse
-
+*/
 
 extension (x: => String) // error
   def f2 = x.reverse