Merge pull request #3374 from dotty-staging/revert-3348

Revert #3348: remove assertion as completion may happen in inferImplicit

Author: odersky

compiler/src/dotty/tools/dotc/typer/Implicits.scala

@@ -708,7 +708,6 @@ trait Implicits { self: Typer =>
     assert(!ctx.isAfterTyper,
       if (argument.isEmpty) i"missing implicit parameter of type $pt after typer"
       else i"type error: ${argument.tpe} does not conform to $pt${err.whyNoMatchStr(argument.tpe, pt)}")
-    val prevConstr = ctx.typerState.constraint
     trace(s"search implicit ${pt.show}, arg = ${argument.show}: ${argument.tpe.show}", implicits, show = true) {
       assert(!pt.isInstanceOf[ExprType])
       val isearch =
@@ -737,7 +736,6 @@ trait Implicits { self: Typer =>
           }
           else result
         case _ =>
-          assert(prevConstr eq ctx.typerState.constraint)
           result
       }
     }

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

@@ -2224,11 +2224,9 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
         if (isFullyDefined(wtp, force = ForceDegree.all) &&
             ctx.typerState.constraint.ne(prevConstraint)) adapt(tree, pt)
         else err.typeMismatch(tree, pt, failure)
-      if (ctx.mode.is(Mode.ImplicitsEnabled)) {
-        val nestedCtx = ctx.fresh.setNewTyperState()
-        inferView(tree, pt)(nestedCtx) match {
+      if (ctx.mode.is(Mode.ImplicitsEnabled))
+        inferView(tree, pt) match {
           case SearchSuccess(inferred, _, _, _) =>
-            nestedCtx.typerState.commit()
             adapt(inferred, pt)(ctx.retractMode(Mode.ImplicitsEnabled))
           case failure: SearchFailure =>
             if (pt.isInstanceOf[ProtoType] && !failure.isInstanceOf[AmbiguousImplicits])
@@ -2238,7 +2236,6 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
               tree
             else recover(failure)
         }
-      }
       else recover(NoImplicitMatches)
     }