Merge pull request #12171 from dotty-staging/fix-11185

Fix #11185: cache pretyped argument with adaptation in FunProto

Author: odersky

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 _ =>

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 =>

tests/pos/i11185.scala

@@ -0,0 +1,14 @@
+class Test:
+  def foo(a: Int, b: Int) = a + b
+
+  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 _)