Harden IDE some more

compiler/src/dotty/tools/dotc/ast/Trees.scala

@@ -115,7 +115,7 @@ object Trees {
      */
     def withType(tpe: Type)(implicit ctx: Context): ThisTree[Type] = {
       if (tpe.isInstanceOf[ErrorType])
-        assert(ctx.reporter.errorsReported)
+        assert(ctx.mode.is(Mode.Interactive) || ctx.reporter.errorsReported)
       else if (Config.checkTreesConsistent)
         checkChildrenTyped(productIterator)
       withTypeUnchecked(tpe)

compiler/src/dotty/tools/dotc/parsing/Parsers.scala

@@ -284,7 +284,16 @@ object Parsers {
     }
 
     def acceptStatSepUnlessAtEnd(altEnd: Token = EOF) =
-      if (!isStatSeqEnd && in.token != altEnd) acceptStatSep()
+      if (!isStatSeqEnd)
+        in.token match {
+          case EOF =>
+          case `altEnd` =>
+          case NEWLINE | NEWLINES => in.nextToken()
+          case SEMI => in.nextToken()
+          case _ =>
+            in.nextToken() // needed to ensure progress; otherwise we might cycle forever
+            accept(SEMI)
+        }
 
     def errorTermTree    = atPos(in.offset) { Literal(Constant(null)) }
 

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

@@ -284,7 +284,8 @@ trait Applications extends Compatibility { self: Typer with Dynamic =>
           case (arg: NamedArg @unchecked) :: _ =>
             val nameAssocs = for (arg @ NamedArg(name, _) <- args) yield (name, arg)
             handleNamed(pnames, args, nameAssocs.toMap, Set())
-          case arg :: args1 => arg :: handlePositional(pnames.tail, args1)
+          case arg :: args1 =>
+            arg :: handlePositional(if (pnames.isEmpty) Nil else pnames.tail, args1)
           case Nil => Nil
         }
 

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

@@ -756,6 +756,7 @@ class Namer { typer: Typer =>
           else levels(c.outer) + 1
         completions.println(s"!!!completing ${denot.symbol.showLocated} in buried typerState, gap = ${levels(ctx)}")
       }
+      assert(ctx.runId == creationContext.runId, "completing $denot in wrong run ${ctx.runId}, was created in ${creationContext.runId}")
       completeInCreationContext(denot)
     }
 

tests/neg/i1779.scala

@@ -8,6 +8,6 @@ object Test {
   def f = {
     val _parent = 3
     q"val hello = $_parent"
-    q"class $_" // error // error
-  }
+    q"class $_" // error
+  } // error
 }