Fix #8188: For the purposes of overloading, contextual methods aren't methodic

Author: anatoliykmetyuk

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

@@ -1783,7 +1783,10 @@ trait Applications extends Compatibility {
     }
 
     def resultIsMethod(tp: Type): Boolean = tp.widen.stripPoly match
-      case tp: MethodType => tp.resultType.isInstanceOf[MethodType]
+      case tp: MethodType =>
+        tp.resultType match
+          case mt: MethodType => !mt.isContextualMethod
+          case _ => false
       case _ => false
 
     val found = narrowMostSpecific(candidates)

tests/pos/i8188.scala

@@ -0,0 +1,11 @@
+object Test {
+  extension StrDeco on (tree: String) {
+    def show(given DummyImplicit): String = ???
+    def show(color: Boolean)(given DummyImplicit): String = ???
+  }
+
+  val a: String = "foo".show
+  val b: String = "foo".show(true)
+  val c: Any = "foo".show
+  val d: Any = "foo".show(true)
+}