WIP try and fail to report this more precisely and fix tests

Author: Blaisorblade

compiler/src/dotty/tools/dotc/core/TypeErrors.scala

@@ -112,8 +112,10 @@ class CyclicReference private (val denot: SymDenotation, var inImplicitSearch: B
         cx.tree match {
           case tree: untpd.ValOrDefDef if inImplicitSearch && !tree.tpt.typeOpt.exists =>
             // Can happen in implicit defs (#4709) or outside (#3253).
-            TermMemberNeedsNeedsResultTypeForImplicitSearch(cycleSym)
+            TermMemberNeedsNeedsResultTypeForImplicitSearch(tree.name)
           case tree: untpd.DefDef if !tree.tpt.typeOpt.exists =>
+            // The reported symbol is more correct, but it might *not* be a method!
+            // OverloadedOrRecursiveMethodNeedsResultType(cycleSym.name)
             OverloadedOrRecursiveMethodNeedsResultType(tree.name)
           case tree: untpd.ValDef if !tree.tpt.typeOpt.exists =>
             RecursiveValueNeedsResultType(tree.name)

compiler/src/dotty/tools/dotc/reporting/diagnostic/messages.scala

@@ -2111,13 +2111,13 @@ object messages {
   }
 
   // Relative of CyclicReferenceInvolvingImplicit and RecursiveValueNeedsResultType
-  case class TermMemberNeedsNeedsResultTypeForImplicitSearch(cycleSym: Symbol)(implicit ctx: Context)
+  case class TermMemberNeedsNeedsResultTypeForImplicitSearch(cycleSymName: Names.TermName)(implicit ctx: Context)
     extends Message(TermMemberNeedsNeedsResultTypeForImplicitSearchID) {
     val kind = "Syntax"
-    val msg = hl"""$cycleSym needs result type because its right-hand side attempts implicit search"""
+    val msg = hl"""Member $cycleSymName needs result type because its right-hand side attempts implicit search"""
     val explanation =
-      hl"""|The right hand-side of $cycleSym's definition requires an implicit search at the highlighted position.
-           |To avoid this error, give `${cycleSym.name}` an explicit type.
+      hl"""|The right hand-side of $cycleSymName's definition requires an implicit search at the highlighted position.
+           |To avoid this error, give `${cycleSymName}` an explicit type.
            |""".stripMargin
   }
 }

compiler/test/dotty/tools/dotc/reporting/ErrorMessagesTests.scala

@@ -291,7 +291,7 @@ class ErrorMessagesTests extends ErrorMessagesTest {
 
         assertMessageCount(1, messages)
         val OverloadedOrRecursiveMethodNeedsResultType(name) :: Nil = messages
-        assertEquals("odd", name.show)
+        assertEquals("even", name.show)
       }
 
   @Test def mutualRecursion_i2001a =
@@ -312,8 +312,8 @@ class ErrorMessagesTests extends ErrorMessagesTest {
         implicit val ctx: Context = ictx
 
         assertMessageCount(1, messages)
-        val CyclicReferenceInvolving(denot) :: Nil = messages
-        assertEquals("value x", denot.show)
+        val OverloadedOrRecursiveMethodNeedsResultType(denot) :: Nil = messages
+        assertEquals("foo", denot.show)
       }
 
 
@@ -333,8 +333,8 @@ class ErrorMessagesTests extends ErrorMessagesTest {
       implicit val ctx: Context = ictx
 
       assertMessageCount(1, messages)
-      val TermMemberNeedsNeedsResultTypeForImplicitSearch(tree) :: Nil = messages
-      assertEquals("x", tree.name.show)
+      val TermMemberNeedsNeedsResultTypeForImplicitSearch(name) :: Nil = messages
+      assertEquals("x", name.show)
     }
 
   @Test def implicitSearchForcesImplicitRetType_i4709 =
@@ -358,8 +358,8 @@ class ErrorMessagesTests extends ErrorMessagesTest {
       implicit val ctx: Context = ictx
 
       assertMessageCount(1, messages)
-      val TermMemberNeedsNeedsResultTypeForImplicitSearch(tree) :: Nil = messages
-      assertEquals("ctx", tree.name.show)
+      val TermMemberNeedsNeedsResultTypeForImplicitSearch(name) :: Nil = messages
+      assertEquals("ctx", name.show)
     }
 
   @Test def implicitSearchForcesNonImplicitRetTypeOnExplicitImport_i3253 =
@@ -376,8 +376,8 @@ class ErrorMessagesTests extends ErrorMessagesTest {
         implicit val ctx: Context = ictx
 
         assertMessageCount(1, messages)
-        val TermMemberNeedsNeedsResultTypeForImplicitSearch(tree) :: Nil = messages
-        assertEquals("test", tree.name.show)
+        val TermMemberNeedsNeedsResultTypeForImplicitSearch(name) :: Nil = messages
+        assertEquals("test", name.show)
       }
 
   @Test def superQualMustBeParent =