Fix auto-suggest breakage and expand test

Author: odersky

compiler/src/dotty/tools/dotc/typer/Applications.scala

@@ -651,7 +651,7 @@ trait Applications extends Compatibility {
    *  argument trees.
    */
   class ApplicableToTrees(methRef: TermRef, args: List[Tree], resultType: Type)(implicit ctx: Context)
-  extends TestApplication(methRef, methRef.widenTermRefExpr, args, resultType) {
+  extends TestApplication(methRef, methRef.widen, args, resultType) {
     def argType(arg: Tree, formal: Type): Type = normalize(arg.tpe, formal)
     def treeToArg(arg: Tree): Tree = arg
     def isVarArg(arg: Tree): Boolean = tpd.isWildcardStarArg(arg)

tests/pos/i4561.scala

@@ -1,10 +1,20 @@
-object abc {
+object abc:
   trait Test0
-  trait Test1 { def apply(f: Int => Int): Unit }
+  trait Test1[T]:
+    def apply(f: T => T): Unit
+    def apply(s: String): Unit
 
   def v: Test0 = ???
-  def v[T]: Test1 = ???
-  //def v[T](x: String): Test0 = ???
+  def v[T]: Test1[Int] = ???
 
-  v[Int]{ v => v }
-}
+  def w: Test0 = ???
+  def w[T]: Test1[T] = ???
+  def w[T](x: String): Test1[T] = ???
+
+  v[Any](x => x)
+  val v1: Test0 = v
+  v(x => x + 1)
+
+  w[Int](_ + 1)
+  // w[_ + 1)      // error: `+` is not a member of Any
+  w[Int]("x")(_ + 1)