Merge MethodType and PolyType functionality where possible

Two benefits: (1) less code. (2) finding subtle bugs about
parameter dependent method types. By merging with PolyTypes
we are forced to take parameter dependencies into account.

5 files changed, 7 insertions, 15 deletions

diff --git a/compiler/src/dotty/tools/dotc/typer/Applications.scala b/compiler/src/dotty/tools/dotc/typer/Applications.scala
index 25c9c13d8..4e43e429b 100644
--- a/compiler/src/dotty/tools/dotc/typer/Applications.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Applications.scala
@@ -1284,8 +1284,7 @@ trait Applications extends Compatibility { self: Typer with Dynamic =>
           case x => x
         }
 
-        def sizeFits(alt: TermRef, tp: Type): Boolean = tp match {
-          case tp: PolyType => sizeFits(alt, tp.resultType)
+        def sizeFits(alt: TermRef, tp: Type): Boolean = tp.stripPoly match {
           case tp: MethodType =>
             val ptypes = tp.paramInfos
             val numParams = ptypes.length
diff --git a/compiler/src/dotty/tools/dotc/typer/Implicits.scala b/compiler/src/dotty/tools/dotc/typer/Implicits.scala
index 703d2fc3c..6c0be51df 100644
--- a/compiler/src/dotty/tools/dotc/typer/Implicits.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Implicits.scala
@@ -107,9 +107,8 @@ object Implicits {
             !(isFunctionInS2 || isImplicitConverter || isConforms)
         }
 
-        def discardForValueType(tpw: Type): Boolean = tpw match {
+        def discardForValueType(tpw: Type): Boolean = tpw.stripPoly match {
           case tpw: MethodType => !tpw.isImplicit
-          case tpw: PolyType => discardForValueType(tpw.resultType)
           case _ => false
         }
 
diff --git a/compiler/src/dotty/tools/dotc/typer/Typer.scala b/compiler/src/dotty/tools/dotc/typer/Typer.scala
index 9a9e45941..723e7007f 100644
--- a/compiler/src/dotty/tools/dotc/typer/Typer.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Typer.scala
@@ -748,7 +748,7 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
           case _ =>
         }
         val ofFun =
-          if (nme.syntheticParamNames(args.length + 1) contains param.name)
+          if (MethodType.syntheticParamNames(args.length + 1) contains param.name)
             i" of expanded function $tree"
           else
             ""
@@ -1285,9 +1285,7 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
      *  @param psym  Its type symbol
      *  @param cinfo The info of its constructor
      */
-    def maybeCall(ref: Tree, psym: Symbol, cinfo: Type): Tree = cinfo match {
-      case cinfo: PolyType =>
-        maybeCall(ref, psym, cinfo.resultType)
+    def maybeCall(ref: Tree, psym: Symbol, cinfo: Type): Tree = cinfo.stripPoly match {
       case cinfo @ MethodType(Nil) if cinfo.resultType.isInstanceOf[ImplicitMethodType] =>
         val icall = New(ref).select(nme.CONSTRUCTOR).appliedToNone
         typedExpr(untpd.TypedSplice(icall))(superCtx)
diff --git a/compiler/src/dotty/tools/dotc/typer/VarianceChecker.scala b/compiler/src/dotty/tools/dotc/typer/VarianceChecker.scala
index d5dd5a024..f88098519 100644
--- a/compiler/src/dotty/tools/dotc/typer/VarianceChecker.scala
+++ b/compiler/src/dotty/tools/dotc/typer/VarianceChecker.scala
@@ -88,10 +88,8 @@ class VarianceChecker()(implicit ctx: Context) {
           if (sym.variance != 0 && base.isContainedIn(sym.owner)) checkVarianceOfSymbol(sym)
           else if (sym.isAliasType) this(status, sym.info.bounds.hi)
           else foldOver(status, tp)
-        case tp: MethodType =>
-          this(status, tp.resultType) // params will be checked in their TypeDef nodes.
-        case tp: PolyType =>
-          this(status, tp.resultType) // params will be checked in their ValDef nodes.
+        case tp: MethodOrPoly =>
+          this(status, tp.resultType) // params will be checked in their TypeDef or ValDef nodes.
         case AnnotatedType(_, annot) if annot.symbol == defn.UncheckedVarianceAnnot =>
           status
         //case tp: ClassInfo =>
diff --git a/compiler/src/dotty/tools/dotc/typer/Variances.scala b/compiler/src/dotty/tools/dotc/typer/Variances.scala
index 83ac23f7e..aeeef0275 100644
--- a/compiler/src/dotty/tools/dotc/typer/Variances.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Variances.scala
@@ -79,7 +79,7 @@ object Variances {
       varianceInType(parent)(tparam) & varianceInType(rinfo)(tparam)
     case tp: RecType =>
       varianceInType(tp.parent)(tparam)
-    case tp: MethodType =>
+    case tp: MethodOrPoly =>
       flip(varianceInTypes(tp.paramInfos)(tparam)) & varianceInType(tp.resultType)(tparam)
     case ExprType(restpe) =>
       varianceInType(restpe)(tparam)
@@ -94,8 +94,6 @@ object Variances {
             v
         }
       varianceInArgs(varianceInType(tycon)(tparam), args, tycon.typeParams)
-    case tp: PolyType =>
-      flip(varianceInTypes(tp.paramInfos)(tparam)) & varianceInType(tp.resultType)(tparam)
     case AnnotatedType(tp, annot) =>
       varianceInType(tp)(tparam) & varianceInAnnot(annot)(tparam)
     case tp: AndOrType =>