SI-6138 Centralize and refine detection of `getClass` calls

`getClass` is special cased in the compiler; this is described
in in the comments on `Definitions.Any_getClass`.

Part of this happens in `Typer#stabilize`. This was trying to determine
if an Ident or Select node was a call to `getClass` by merits of the name
of the tree's symbol and by checking that the its type (if it was a
MethodType or PolyType) had no parameters in the primary parameter list.

Overloaded user defined `getClass` methods confused this check. In the
enclosed test case, the tree `definitions.this.getClass` had an
`OverloadedType`, and such types always report an empty list of `params`.

This commit:

  - changes `stabilize` to use `isGetClass`, rather than the
    homebrew check
  - changes `isGetClass` to consider a `Set[Symbol]` containing all
    `getClass` variants. This moves some similar code from `Erasure`
    to `Definitions`
  - keeps a fast negative path in `isGetClass` based on the symbol's name

1 files changed, 8 insertions, 0 deletions

diff --git a/bincompat-forward.whitelist.conf b/bincompat-forward.whitelist.conf
index 83864f48ee..284e0809a8 100644
--- a/bincompat-forward.whitelist.conf
+++ b/bincompat-forward.whitelist.conf
@@ -471,6 +471,14 @@ filter {
         {
              matchName="scala.concurrent.impl.Promise$CompletionLatch"
              problemName=MissingClassProblem
+        },
+        {
+            matchName="scala.reflect.internal.Definitions#DefinitionsClass.getClassMethods"
+            problemName=MissingMethodProblem
+        },
+        {
+            matchName="scala.reflect.internal.Definitions#DefinitionsClass.primitiveGetClassMethods"
+            problemName=MissingMethodProblem
         }
     ]
 }