From a16edc4eaa33aebcede467b35faba0ed5eab0c66 Mon Sep 17 00:00:00 2001
From: Liu Fengyun <liu@fengy.me>
Date: Wed, 21 Apr 2021 13:59:33 +0200
Subject: [PATCH 1/2] Fix #11185: cache pretyped argument with adaptation in
 FunProto

---
 compiler/src/dotty/tools/dotc/typer/Applications.scala | 6 +++++-
 compiler/src/dotty/tools/dotc/typer/ProtoTypes.scala   | 4 ++++
 tests/pos/i11185.scala                                 | 5 +++++
 3 files changed, 14 insertions(+), 1 deletion(-)
 create mode 100644 tests/pos/i11185.scala

diff --git a/compiler/src/dotty/tools/dotc/typer/Applications.scala b/compiler/src/dotty/tools/dotc/typer/Applications.scala
index 4f87d0741be3..2d30b925a7eb 100644
--- a/compiler/src/dotty/tools/dotc/typer/Applications.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Applications.scala
@@ -2101,7 +2101,11 @@ trait Applications extends Compatibility {
             else defn.FunctionOf(commonParamTypes, WildcardType)
           overload.println(i"pretype arg $arg with expected type $commonFormal")
           if (commonParamTypes.forall(isFullyDefined(_, ForceDegree.flipBottom)))
-            withMode(Mode.ImplicitsEnabled)(pt.typedArg(arg, commonFormal))
+            withMode(Mode.ImplicitsEnabled) {
+              // We can cache the adapted argument here because the expected type
+              // is a common type shared by all overloading candidates.
+              pt.cacheArg(arg, pt.typedArg(arg, commonFormal))
+            }
         }
         recur(altFormals.map(_.tail), args1)
       case _ =>
diff --git a/compiler/src/dotty/tools/dotc/typer/ProtoTypes.scala b/compiler/src/dotty/tools/dotc/typer/ProtoTypes.scala
index 0d2c60c677b0..bc479b51b052 100644
--- a/compiler/src/dotty/tools/dotc/typer/ProtoTypes.scala
+++ b/compiler/src/dotty/tools/dotc/typer/ProtoTypes.scala
@@ -424,6 +424,10 @@ object ProtoTypes {
       if (t == null) NoType else t.tpe
     }
 
+    /** Cache the typed argument */
+    def cacheArg(arg: untpd.Tree, targ: Tree) =
+      state.typedArg = state.typedArg.updated(arg, targ)
+
     /** The same proto-type but with all arguments combined in a single tuple */
     def tupledDual: FunProto = state.tupledDual match {
       case pt: FunProto =>
diff --git a/tests/pos/i11185.scala b/tests/pos/i11185.scala
new file mode 100644
index 000000000000..8bb407b6cebb
--- /dev/null
+++ b/tests/pos/i11185.scala
@@ -0,0 +1,5 @@
+class Test:
+  def foo(a: Int, b: Int) = a + b
+
+  Map(1 -> 2).map(foo _)
+  Map(1 -> 2).map(foo)

From 1bf1b3fab3da0b6af7ac13036a45b47c0450e9f8 Mon Sep 17 00:00:00 2001
From: Liu Fengyun <liu@fengy.me>
Date: Wed, 21 Apr 2021 15:17:58 +0200
Subject: [PATCH 2/2] Add another test: in case Map.map becomes non-overloaded
 (thanks @Jasper-M)

---
 tests/pos/i11185.scala | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/tests/pos/i11185.scala b/tests/pos/i11185.scala
index 8bb407b6cebb..3b4a308bbc9e 100644
--- a/tests/pos/i11185.scala
+++ b/tests/pos/i11185.scala
@@ -3,3 +3,12 @@ class Test:
 
   Map(1 -> 2).map(foo _)
   Map(1 -> 2).map(foo)
+
+class Test2:
+  def foo(a: Int, b: Int) = a + b
+
+  def bar(f: ((Int, Int)) => Int) = "ok"
+  def bar(f: ((Int, Int)) => String)(using Int) = "ok"
+
+  bar(foo)
+  bar(foo _)