Hooks to check that comparisons with == / != make sense

Also, check that pattern matching against idents/selects/literals makes
sense.

The hooks perform an implicit search for an instance of `Eq[L, R]`, where
`L`, `R` are the argument types. So far this always succeeeds because Eq.eqAny
matches all such types. A separate commit will check the returned
search term for validity.

1 files changed, 7 insertions, 0 deletions

diff --git a/src/dotty/tools/dotc/core/Definitions.scala b/src/dotty/tools/dotc/core/Definitions.scala
index 7f59cbed0..b99d0716b 100644
--- a/src/dotty/tools/dotc/core/Definitions.scala
+++ b/src/dotty/tools/dotc/core/Definitions.scala
@@ -424,10 +424,17 @@ class Definitions {
   lazy val LanguageModuleRef          = ctx.requiredModule("dotty.language")
   def LanguageModuleClass(implicit ctx: Context) = LanguageModuleRef.symbol.moduleClass.asClass
   lazy val NonLocalReturnControlType: TypeRef   = ctx.requiredClassRef("scala.runtime.NonLocalReturnControl")
+
   lazy val ClassTagType = ctx.requiredClassRef("scala.reflect.ClassTag")
   def ClassTagClass(implicit ctx: Context) = ClassTagType.symbol.asClass
   def ClassTagModule(implicit ctx: Context) = ClassTagClass.companionModule
 
+  lazy val EqType = ctx.requiredClassRef("scala.Eq")
+  def EqClass(implicit ctx: Context) = EqType.symbol.asClass
+  def EqModule(implicit ctx: Context) = EqClass.companionModule
+
+    def Eq_eqAny(implicit ctx: Context) = EqModule.requiredMethodRef(nme.eqAny)
+
   // Annotation base classes
   lazy val AnnotationType              = ctx.requiredClassRef("scala.annotation.Annotation")
   def AnnotationClass(implicit ctx: Context) = AnnotationType.symbol.asClass