Make it easier to fail

Author: som-snytt

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

@@ -3113,15 +3113,13 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
      *  parameters of the current class are also defined.
      */
     def implementDeferredGivens(body: List[Tree]): List[Tree] =
-      def isGivenValue(mbr: TermRef) =
-        val dcl = mbr.symbol
-        if dcl.is(Method) then
-          report.error(
-            em"""Cannot infer the implementation of the deferred ${dcl.showLocated}
-                |since that given is parameterized. An implementing given needs to be written explicitly.""",
-            cdef.srcPos)
-          false
-        else true
+      def failFor(mbr: TermRef, why: String): false =
+        report.error(
+          em"""Cannot infer the implementation of the deferred ${mbr.symbol.showLocated}
+              |since $why. An implementing given needs to be written explicitly.""",
+          cdef.srcPos)
+        false
+      def isGivenValue(mbr: TermRef) = !mbr.symbol.is(Method) || failFor(mbr, "that given is parameterized")
 
       def willBeImplementedInParentClass(m: TermRef) =
         val superCls = cls.superClass