Fix to primaryConstructor

Primary constructor was picking last constructor instead of first one.
This is now fixed. Also, added paramAccessors utility method.

Author: odersky

src/dotty/tools/dotc/core/Contexts.scala

@@ -282,7 +282,7 @@ object Contexts {
      *    from constructor parameters to class paramater accessors.
      */
     def superCallContext: Context = {
-      val locals = newScopeWith(owner.decls.filter(_ is ParamAccessor).toList: _*)
+      val locals = newScopeWith(owner.asClass.paramAccessors: _*)
       superOrThisCallContext(owner.primaryConstructor, locals)
     }
 

src/dotty/tools/dotc/core/Denotations.scala

@@ -676,6 +676,7 @@ object Denotations {
     // ------ PreDenotation ops ----------------------------------------------
 
     final def first = this
+    final def last = this
     final def toDenot(pre: Type)(implicit ctx: Context): Denotation = this
     final def containsSym(sym: Symbol): Boolean = hasUniqueSym && (symbol eq sym)
     final def containsSig(sig: Signature)(implicit ctx: Context) =
@@ -761,8 +762,9 @@ object Denotations {
     /** A denotation in the group exists */
     def exists: Boolean
 
-    /** First denotation in the group */
+    /** First/last denotation in the group */
     def first: Denotation
+    def last: Denotation
 
     /** Convert to full denotation by &-ing all elements */
     def toDenot(pre: Type)(implicit ctx: Context): Denotation
@@ -827,6 +829,7 @@ object Denotations {
     assert(denots1.exists && denots2.exists, s"Union of non-existing denotations ($denots1) and ($denots2)")
     def exists = true
     def first = denots1.first
+    def last = denots2.last
     def toDenot(pre: Type)(implicit ctx: Context) =
       (denots1 toDenot pre) & (denots2 toDenot pre, pre)
     def containsSym(sym: Symbol) =

src/dotty/tools/dotc/core/SymDenotations.scala

@@ -431,7 +431,7 @@ object SymDenotations {
 
     /** Does this symbol denote the primary constructor of its enclosing class? */
     final def isPrimaryConstructor(implicit ctx: Context) =
-      isConstructor && owner.primaryConstructor == this
+      isConstructor && owner.primaryConstructor == symbol
 
     /** Is this a subclass of the given class `base`? */
     def isSubClass(base: Symbol)(implicit ctx: Context) = false
@@ -1406,9 +1406,15 @@ object SymDenotations {
 
     override def primaryConstructor(implicit ctx: Context): Symbol = {
       val cname = if (this is ImplClass) nme.IMPLCLASS_CONSTRUCTOR else nme.CONSTRUCTOR
-      decls.denotsNamed(cname).first.symbol
+      decls.denotsNamed(cname).last.symbol // denotsNamed returns Symbols in reverse order of occurrence
     }
 
+    /** The parameter accessors of this class. Term and type accessors,
+     *  getters and setters are all returned int his list
+     */
+    def paramAccessors(implicit ctx: Context): List[Symbol] =
+      decls.filter(_ is ParamAccessor).toList
+
     /** If this class has the same `decls` scope reference in `phase` and
      *  `phase.next`, install a new denotation with a cloned scope in `phase.next`.
      */