Harden ReTyper so that it's fit for inlining

1. Imlement typedUnapply
2. Disable implicit view searches and searches
   for equality checks - these should have already
   happened in the first typer run.

Author: odersky

src/dotty/tools/dotc/typer/Applications.scala

@@ -862,7 +862,7 @@ trait Applications extends Compatibility { self: Typer with Dynamic =>
   /** A typed unapply hook, can be overridden by re any-typers between frontend
    *  and pattern matcher.
    */
-  def typedUnApply(tree: untpd.UnApply, selType: Type)(implicit ctx: Context) =
+  def typedUnApply(tree: untpd.UnApply, selType: Type)(implicit ctx: Context): UnApply =
     throw new UnsupportedOperationException("cannot type check an UnApply node")
 
   /** Is given method reference applicable to type arguments `targs` and argument trees `args`?

src/dotty/tools/dotc/typer/ReTyper.scala

@@ -10,6 +10,7 @@ import typer.ProtoTypes._
 import ast.{tpd, untpd}
 import ast.Trees._
 import scala.util.control.NonFatal
+import util.Positions.Position
 import config.Printers.typr
 
 /** A version of Typer that keeps all symbols defined and referenced in a
@@ -62,6 +63,13 @@ class ReTyper extends Typer {
     untpd.cpy.Bind(tree)(tree.name, body1).withType(tree.typeOpt)
   }
 
+  override def typedUnApply(tree: untpd.UnApply, selType: Type)(implicit ctx: Context): UnApply = {
+    val fun1 = typedExpr(tree.fun, AnyFunctionProto)
+    val implicits1 = tree.implicits.map(typedExpr(_))
+    val patterns1 = tree.patterns.mapconserve(pat => typed(pat, pat.tpe))
+    untpd.cpy.UnApply(tree)(fun1, implicits1, patterns1).withType(tree.tpe)
+  }
+
   override def localDummy(cls: ClassSymbol, impl: untpd.Template)(implicit ctx: Context) = impl.symbol
 
   override def retrieveSym(tree: untpd.Tree)(implicit ctx: Context): Symbol = tree.symbol
@@ -99,4 +107,7 @@ class ReTyper extends Typer {
     }
 
   override def checkVariance(tree: Tree)(implicit ctx: Context) = ()
+  override def inferView(from: Tree, to: Type)(implicit ctx: Context): Implicits.SearchResult =
+    Implicits.NoImplicitMatches
+  override def checkCanEqual(ltp: Type, rtp: Type, pos: Position)(implicit ctx: Context): Unit = ()
 }

src/dotty/tools/dotc/typer/Typer.scala

@@ -1533,7 +1533,7 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
     }
   }
 
-  def adapt(tree: Tree, pt: Type, original: untpd.Tree = untpd.EmptyTree)(implicit ctx: Context) = /*>|>*/ track("adapt") /*<|<*/ {
+  def adapt(tree: Tree, pt: Type, original: untpd.Tree = untpd.EmptyTree)(implicit ctx: Context): Tree = /*>|>*/ track("adapt") /*<|<*/ {
     /*>|>*/ ctx.traceIndented(i"adapting $tree of type ${tree.tpe} to $pt", typr, show = true) /*<|<*/ {
       if (tree.isDef) interpolateUndetVars(tree, tree.symbol)
       else if (!tree.tpe.widen.isInstanceOf[MethodOrPoly]) interpolateUndetVars(tree, NoSymbol)