Make PC more resiliant to crashes (#19488)

When working with code that is recovered from errors, we should use
`typeOpt` instead of `tpe` as it can sometimes be null. The added test
cases were the exact snippet that previously failed. I took this
opportunity to change all calls to `tpe` to `typeOpt`.

Author: tgodzik

compiler/src/dotty/tools/dotc/interactive/Completion.scala

@@ -184,12 +184,12 @@ object Completion:
     val completions = adjustedPath match
         // Ignore synthetic select from `This` because in code it was `Ident`
         // See example in dotty.tools.languageserver.CompletionTest.syntheticThis
-        case Select(qual @ This(_), _) :: _ if qual.span.isSynthetic  => completer.scopeCompletions
-        case Select(qual, _) :: _           if qual.tpe.hasSimpleKind => completer.selectionCompletions(qual)
-        case Select(qual, _) :: _                                     => Map.empty
-        case (tree: ImportOrExport) :: _                              => completer.directMemberCompletions(tree.expr)
-        case (_: untpd.ImportSelector) :: Import(expr, _) :: _        => completer.directMemberCompletions(expr)
-        case _                                                        => completer.scopeCompletions
+        case Select(qual @ This(_), _) :: _ if qual.span.isSynthetic      => completer.scopeCompletions
+        case Select(qual, _) :: _           if qual.typeOpt.hasSimpleKind => completer.selectionCompletions(qual)
+        case Select(qual, _) :: _                                         => Map.empty
+        case (tree: ImportOrExport) :: _                                  => completer.directMemberCompletions(tree.expr)
+        case (_: untpd.ImportSelector) :: Import(expr, _) :: _            => completer.directMemberCompletions(expr)
+        case _                                                            => completer.scopeCompletions
 
     val describedCompletions = describeCompletions(completions)
     val backtickedCompletions =
@@ -348,7 +348,7 @@ object Completion:
     /** Widen only those types which are applied or are exactly nothing
      */
     def widenQualifier(qual: Tree)(using Context): Tree =
-      qual.tpe.widenDealias match
+      qual.typeOpt.widenDealias match
         case widenedType if widenedType.isExactlyNothing => qual.withType(widenedType)
         case appliedType: AppliedType => qual.withType(appliedType)
         case _ => qual
@@ -368,10 +368,10 @@ object Completion:
      *  These include inherited definitions but not members added by extensions or implicit conversions
      */
     def directMemberCompletions(qual: Tree)(using Context): CompletionMap =
-      if qual.tpe.isExactlyNothing then
+      if qual.typeOpt.isExactlyNothing then
         Map.empty
       else
-        accessibleMembers(qual.tpe).groupByName
+        accessibleMembers(qual.typeOpt).groupByName
 
     /** Completions introduced by imports directly in this context.
      *  Completions from outer contexts are not included.
@@ -415,7 +415,7 @@ object Completion:
 
     /** Completions from implicit conversions including old style extensions using implicit classes */
     private def implicitConversionMemberCompletions(qual: Tree)(using Context): CompletionMap =
-      if qual.tpe.isExactlyNothing || qual.tpe.isNullType then
+      if qual.typeOpt.isExactlyNothing || qual.typeOpt.isNullType then
         Map.empty
       else
         implicitConversionTargets(qual)(using ctx.fresh.setExploreTyperState())
@@ -432,7 +432,7 @@ object Completion:
       def tryApplyingReceiverToExtension(termRef: TermRef): Option[SingleDenotation] =
         ctx.typer.tryApplyingExtensionMethod(termRef, qual)
           .map { tree =>
-            val tpe = asDefLikeType(tree.tpe.dealias)
+            val tpe = asDefLikeType(tree.typeOpt.dealias)
             termRef.denot.asSingleDenotation.mapInfo(_ => tpe)
           }
 
@@ -453,16 +453,16 @@ object Completion:
 
       // 1. The extension method is visible under a simple name, by being defined or inherited or imported in a scope enclosing the reference.
       val termCompleter = new Completer(Mode.Term, prefix, pos)
-      val extMethodsInScope = termCompleter.scopeCompletions.toList.flatMap {
-        case (name, denots) => denots.collect { case d: SymDenotation if d.isTerm => (d.termRef, name.asTermName) }
-      }
+      val extMethodsInScope = termCompleter.scopeCompletions.toList.flatMap:
+        case (name, denots) => denots.collect:
+          case d: SymDenotation if d.isTerm && d.termRef.symbol.is(Extension) => (d.termRef, name.asTermName)
 
       // 2. The extension method is a member of some given instance that is visible at the point of the reference.
       val givensInScope = ctx.implicits.eligible(defn.AnyType).map(_.implicitRef.underlyingRef)
       val extMethodsFromGivensInScope = extractMemberExtensionMethods(givensInScope)
 
       // 3. The reference is of the form r.m and the extension method is defined in the implicit scope of the type of r.
-      val implicitScopeCompanions = ctx.run.nn.implicitScope(qual.tpe).companionRefs.showAsList
+      val implicitScopeCompanions = ctx.run.nn.implicitScope(qual.typeOpt).companionRefs.showAsList
       val extMethodsFromImplicitScope = extractMemberExtensionMethods(implicitScopeCompanions)
 
       // 4. The reference is of the form r.m and the extension method is defined in some given instance in the implicit scope of the type of r.
@@ -472,7 +472,7 @@ object Completion:
       val availableExtMethods = extMethodsFromGivensInImplicitScope ++ extMethodsFromImplicitScope ++ extMethodsFromGivensInScope ++ extMethodsInScope
       val extMethodsWithAppliedReceiver = availableExtMethods.flatMap {
         case (termRef, termName) =>
-          if termRef.symbol.is(ExtensionMethod) && !qual.tpe.isBottomType then
+          if termRef.symbol.is(ExtensionMethod) && !qual.typeOpt.isBottomType then
             tryApplyingReceiverToExtension(termRef)
               .map(denot => termName -> denot)
           else None
@@ -551,21 +551,25 @@ object Completion:
      * @param qual The argument to which the implicit conversion should be applied.
      * @return The set of types after `qual` implicit conversion.
      */
-    private def implicitConversionTargets(qual: Tree)(using Context): Set[Type] = {
+    private def implicitConversionTargets(qual: Tree)(using Context): Set[Type] =
       val typer = ctx.typer
-      val conversions = new typer.ImplicitSearch(defn.AnyType, qual, pos.span).allImplicits
-      val targets = conversions.map(_.tree.tpe)
+      val targets = try {
+        val conversions = new typer.ImplicitSearch(defn.AnyType, qual, pos.span).allImplicits
+        conversions.map(_.tree.typeOpt)
+      } catch {
+        case _ =>
+          interactiv.println(i"implicit conversion targets failed: ${qual.show}")
+          Set.empty
+      }
 
       interactiv.println(i"implicit conversion targets considered: ${targets.toList}%, %")
       targets
-    }
 
     /** Filter for names that should appear when looking for completions. */
-    private object completionsFilter extends NameFilter {
+    private object completionsFilter extends NameFilter:
       def apply(pre: Type, name: Name)(using Context): Boolean =
         !name.isConstructorName && name.toTermName.info.kind == SimpleNameKind
       def isStable = true
-    }
 
     extension (denotations: Seq[SingleDenotation])
       def groupByName(using Context): CompletionMap = denotations.groupBy(_.name)

presentation-compiler/src/main/dotty/tools/pc/ConvertToNamedArgumentsProvider.scala

@@ -35,7 +35,7 @@ final class ConvertToNamedArgumentsProvider(
     val tree = Interactive.pathTo(trees, pos)(using newctx).headOption
 
     def paramss(fun: tpd.Tree)(using Context): List[String] =
-      fun.tpe match
+      fun.typeOpt match
         case m: MethodType => m.paramNamess.flatten.map(_.toString)
         case _ =>
           fun.symbol.rawParamss.flatten

presentation-compiler/src/main/dotty/tools/pc/ExtractMethodProvider.scala

@@ -128,7 +128,7 @@ final class ExtractMethodProvider(
       yield
         val defnPos = stat.sourcePos
         val extractedPos = head.sourcePos.withEnd(expr.sourcePos.end)
-        val exprType = prettyPrint(expr.tpe.widen)
+        val exprType = prettyPrint(expr.typeOpt.widen)
         val name =
           genName(indexedCtx.scopeSymbols.map(_.decodedName).toSet, "newMethod")
         val (methodParams, typeParams) =

presentation-compiler/src/main/dotty/tools/pc/HoverProvider.scala

@@ -48,7 +48,7 @@ object HoverProvider:
     val indexedContext = IndexedContext(ctx)
 
     def typeFromPath(path: List[Tree]) =
-      if path.isEmpty then NoType else path.head.tpe
+      if path.isEmpty then NoType else path.head.typeOpt
 
     val tp = typeFromPath(path)
     val tpw = tp.widenTermRefExpr
@@ -185,7 +185,7 @@ object HoverProvider:
             findRefinement(parent)
           case _ => None
 
-      val refTpe = sel.tpe.widen.metalsDealias match
+      val refTpe = sel.typeOpt.widen.metalsDealias match
         case r: RefinedType => Some(r)
         case t: (TermRef | TypeProxy) => Some(t.termSymbol.info.metalsDealias)
         case _ => None

presentation-compiler/src/main/dotty/tools/pc/InferredTypeProvider.scala

@@ -138,7 +138,7 @@ final class InferredTypeProvider(
           adjustOpt.foreach(adjust => endPos.setEnd(adjust.adjustedEndPos))
           new TextEdit(
             endPos,
-            ": " + printType(optDealias(tpt.tpe)) + {
+            ": " + printType(optDealias(tpt.typeOpt)) + {
               if withParens then ")" else ""
             }
           )
@@ -211,7 +211,7 @@ final class InferredTypeProvider(
           adjustOpt.foreach(adjust => end.setEnd(adjust.adjustedEndPos))
           new TextEdit(
             end,
-            ": " + printType(optDealias(tpt.tpe))
+            ": " + printType(optDealias(tpt.typeOpt))
           )
         end typeNameEdit
 
@@ -241,7 +241,7 @@ final class InferredTypeProvider(
         def baseEdit(withParens: Boolean) =
           new TextEdit(
             bind.endPos.toLsp,
-            ": " + printType(optDealias(body.tpe)) + {
+            ": " + printType(optDealias(body.typeOpt)) + {
               if withParens then ")" else ""
             }
           )
@@ -274,7 +274,7 @@ final class InferredTypeProvider(
       case Some(i @ Ident(name)) =>
         val typeNameEdit = new TextEdit(
           i.endPos.toLsp,
-          ": " + printType(optDealias(i.tpe.widen))
+          ": " + printType(optDealias(i.typeOpt.widen))
         )
         typeNameEdit :: imports
 

presentation-compiler/src/main/dotty/tools/pc/MetalsInteractive.scala

@@ -190,7 +190,7 @@ object MetalsInteractive:
        */
       case (tpt: TypeTree) :: parent :: _
           if tpt.span != parent.span && !tpt.symbol.is(Synthetic) =>
-        List((tpt.symbol, tpt.tpe))
+        List((tpt.symbol, tpt.typeOpt))
 
       /* TypeTest class https://dotty.epfl.ch/docs/reference/other-new-features/type-test.html
        * compiler automatically adds unapply if possible, we need to find the type symbol

presentation-compiler/src/main/dotty/tools/pc/PcDefinitionProvider.scala

@@ -108,7 +108,7 @@ class PcDefinitionProvider(
       case Nil =>
         path.headOption match
           case Some(value: Literal) =>
-            definitionsForSymbol(List(value.tpe.widen.typeSymbol), pos)
+            definitionsForSymbol(List(value.typeOpt.widen.typeSymbol), pos)
           case _ => DefinitionResultImpl.empty
       case _ =>
         definitionsForSymbol(typeSymbols, pos)

presentation-compiler/src/main/dotty/tools/pc/PcSyntheticDecorationProvider.scala

@@ -114,7 +114,7 @@ final class PcSyntheticDecorationsProvider(
   ): String =
     val tpdPath =
       Interactive.pathTo(unit.tpdTree, pos.span)
-    
+
     val indexedCtx = IndexedContext(Interactive.contextOfPath(tpdPath))
     val printer = ShortenedTypePrinter(
       symbolSearch
@@ -210,7 +210,7 @@ object TypeParameters:
           case sel: Select if sel.isInfix =>
             sel.sourcePos.withEnd(sel.nameSpan.end)
           case _ => fun.sourcePos
-        val tpes = args.map(_.tpe.stripTypeVar.widen.finalResultType)
+        val tpes = args.map(_.typeOpt.stripTypeVar.widen.finalResultType)
         Some((tpes, pos.endPos, fun))
       case _ => None
   private def inferredTypeArgs(args: List[Tree]): Boolean =
@@ -232,15 +232,15 @@ object InferredType:
             !vd.symbol.is(Flags.Enum) &&
             !isValDefBind(text, vd) =>
         if vd.symbol == vd.symbol.sourceSymbol then
-          Some(tpe.tpe, tpe.sourcePos.withSpan(vd.nameSpan), vd)
+          Some(tpe.typeOpt, tpe.sourcePos.withSpan(vd.nameSpan), vd)
         else None
       case vd @ DefDef(_, _, tpe, _)
           if isValidSpan(tpe.span, vd.nameSpan) &&
             tpe.span.start >= vd.nameSpan.end &&
             !vd.symbol.isConstructor &&
             !vd.symbol.is(Flags.Mutable) =>
         if vd.symbol == vd.symbol.sourceSymbol then
-          Some(tpe.tpe, tpe.sourcePos, vd)
+          Some(tpe.typeOpt, tpe.sourcePos, vd)
         else None
       case bd @ Bind(
             name,
@@ -290,4 +290,4 @@ case class Synthetics(
 end Synthetics
 
 object Synthetics:
-  def empty: Synthetics = Synthetics(Nil, Set.empty)
+  def empty: Synthetics = Synthetics(Nil, Set.empty)

presentation-compiler/src/main/dotty/tools/pc/completions/Completions.scala

@@ -119,7 +119,7 @@ class Completions(
           // should not show completions for toplevel
           case Nil | (_: PackageDef) :: _ if pos.source.file.extension != "sc" =>
             (allAdvanced, SymbolSearch.Result.COMPLETE)
-          case Select(qual, _) :: _ if qual.tpe.isErroneous =>
+          case Select(qual, _) :: _ if qual.typeOpt.isErroneous =>
             (allAdvanced, SymbolSearch.Result.COMPLETE)
           case Select(qual, _) :: _ =>
             val (_, compilerCompletions) = Completion.completions(pos)
@@ -749,7 +749,7 @@ class Completions(
         items
 
     def forSelect(sel: Select): CompletionApplication =
-      val tpe = sel.qualifier.tpe
+      val tpe = sel.qualifier.typeOpt
       val members = tpe.allMembers.map(_.symbol).toSet
 
       new CompletionApplication:

presentation-compiler/src/main/dotty/tools/pc/completions/MatchCaseCompletions.scala

@@ -74,8 +74,8 @@ object CaseKeywordCompletion:
     val parents: Parents = selector match
       case EmptyTree =>
         val seenFromType = parent match
-          case TreeApply(fun, _) if !fun.tpe.isErroneous => fun.tpe
-          case _ => parent.tpe
+          case TreeApply(fun, _) if !fun.typeOpt.isErroneous => fun.typeOpt
+          case _ => parent.typeOpt
         seenFromType.paramInfoss match
           case (head :: Nil) :: _
               if definitions.isFunctionType(head) || head.isRef(
@@ -84,7 +84,7 @@ object CaseKeywordCompletion:
             val argTypes = head.argTypes.init
             new Parents(argTypes, definitions)
           case _ => new Parents(NoType, definitions)
-      case sel => new Parents(sel.tpe, definitions)
+      case sel => new Parents(sel.typeOpt, definitions)
 
     val selectorSym = parents.selector.widen.metalsDealias.typeSymbol
 
@@ -240,7 +240,7 @@ object CaseKeywordCompletion:
       completionPos,
       clientSupportsSnippets
     )
-    val tpe = selector.tpe.widen.metalsDealias.bounds.hi match
+    val tpe = selector.typeOpt.widen.metalsDealias.bounds.hi match
       case tr @ TypeRef(_, _) => tr.underlying
       case t => t