Safe equality for core classes:

Name, Symbol, Denotation, Type.

This uncovered two nonsensical comparisons, one in CollectEntryPoints,
the other in DottyBackendInterface.

6 files changed, 14 insertions, 6 deletions

diff --git a/src/dotty/tools/backend/jvm/DottyBackendInterface.scala b/src/dotty/tools/backend/jvm/DottyBackendInterface.scala
index a64ce5900..002a6bf27 100644
--- a/src/dotty/tools/backend/jvm/DottyBackendInterface.scala
+++ b/src/dotty/tools/backend/jvm/DottyBackendInterface.scala
@@ -861,11 +861,11 @@ class DottyBackendInterface(outputDirectory: AbstractFile)(implicit ctx: Context
               "If possible, please file a bug on issues.scala-lang.org.")
 
           tp match {
-            case ThisType(ArrayClass)               => ObjectReference.asInstanceOf[ct.bTypes.ClassBType] // was introduced in 9b17332f11 to fix SI-999, but this code is not reached in its test, or any other test
-            case ThisType(sym)                      => storage.getClassBTypeAndRegisterInnerClass(sym.asInstanceOf[ct.int.Symbol])
-           // case t: SingletonType                 => primitiveOrClassToBType(t.classSymbol)
-            case t: SingletonType                  => t.underlying.toTypeKind(ct)(storage)
-            case t: RefinedType                   =>  t.parent.toTypeKind(ct)(storage) //parents.map(_.toTypeKind(ct)(storage).asClassBType).reduceLeft((a, b) => a.jvmWiseLUB(b))
+            case tp: ThisType if tp.cls == ArrayClass => ObjectReference.asInstanceOf[ct.bTypes.ClassBType] // was introduced in 9b17332f11 to fix SI-999, but this code is not reached in its test, or any other test
+            case tp: ThisType                         => storage.getClassBTypeAndRegisterInnerClass(tp.cls.asInstanceOf[ct.int.Symbol])
+           // case t: SingletonType                   => primitiveOrClassToBType(t.classSymbol)
+            case t: SingletonType                     => t.underlying.toTypeKind(ct)(storage)
+            case t: RefinedType                       =>  t.parent.toTypeKind(ct)(storage) //parents.map(_.toTypeKind(ct)(storage).asClassBType).reduceLeft((a, b) => a.jvmWiseLUB(b))
           }
       }
     }
diff --git a/src/dotty/tools/dotc/core/Denotations.scala b/src/dotty/tools/dotc/core/Denotations.scala
index 080e8a39b..69624b01a 100644
--- a/src/dotty/tools/dotc/core/Denotations.scala
+++ b/src/dotty/tools/dotc/core/Denotations.scala
@@ -70,6 +70,8 @@ import Decorators.SymbolIteratorDecorator
  */
 object Denotations {
 
+  implicit def eqDenotation: Eq[Denotation, Denotation] = Eq
+
   /** A denotation is the result of resolving
    *  a name (either simple identifier or select) during a given period.
    *
diff --git a/src/dotty/tools/dotc/core/Names.scala b/src/dotty/tools/dotc/core/Names.scala
index 10eef16c1..223d95045 100644
--- a/src/dotty/tools/dotc/core/Names.scala
+++ b/src/dotty/tools/dotc/core/Names.scala
@@ -26,6 +26,8 @@ object Names {
     def toTermName: TermName
   }
 
+  implicit def eqName: Eq[Name, Name] = Eq
+
   /** A name is essentially a string, with three differences
    *  1. Names belong in one of two name spaces: they are type names or term names.
    *     Term names have a sub-category of "local" field names.
diff --git a/src/dotty/tools/dotc/core/Symbols.scala b/src/dotty/tools/dotc/core/Symbols.scala
index d40acdfa7..473f107cb 100644
--- a/src/dotty/tools/dotc/core/Symbols.scala
+++ b/src/dotty/tools/dotc/core/Symbols.scala
@@ -361,6 +361,8 @@ trait Symbols { this: Context =>
 
 object Symbols {
 
+  implicit def eqSymbol: Eq[Symbol, Symbol] = Eq
+
   /** A Symbol represents a Scala definition/declaration or a package.
    *  @param coord  The coordinates of the symbol (a position or an index)
    *  @param id     A unique identifier of the symbol (unique per ContextBase)
diff --git a/src/dotty/tools/dotc/core/Types.scala b/src/dotty/tools/dotc/core/Types.scala
index 114e6c908..71ea6d2b3 100644
--- a/src/dotty/tools/dotc/core/Types.scala
+++ b/src/dotty/tools/dotc/core/Types.scala
@@ -38,6 +38,8 @@ object Types {
 
   @sharable private var nextId = 0
 
+  implicit def eqType: Eq[Type, Type] = Eq
+
   /** The class of types.
    *  The principal subclasses and sub-objects are as follows:
    *
diff --git a/src/dotty/tools/dotc/transform/CollectEntryPoints.scala b/src/dotty/tools/dotc/transform/CollectEntryPoints.scala
index b85c44647..714255962 100644
--- a/src/dotty/tools/dotc/transform/CollectEntryPoints.scala
+++ b/src/dotty/tools/dotc/transform/CollectEntryPoints.scala
@@ -75,7 +75,7 @@ class CollectEntryPoints extends MiniPhaseTransform {
       val javaPlatform = ctx.platform.asInstanceOf[JavaPlatform]
       if (javaPlatform.hasJavaMainMethod(companion))
         failNoForwarder("companion contains its own main method")
-      else if (companion != NoSymbol && companion.info.member(nme.main) != NoSymbol)
+      else if (companion.exists && companion.info.member(nme.main).exists)
       // this is only because forwarders aren't smart enough yet
         failNoForwarder("companion contains its own main method (implementation restriction: no main is allowed, regardless of signature)")
       else if (companion.flags is Flags.Trait)