Fix crash in member selection from type cast

Author: liufengyun

compiler/src/dotty/tools/dotc/transform/init/Errors.scala

@@ -18,55 +18,57 @@ object Errors:
 
     def pos(using Context): SourcePosition = trace.last.sourcePos
 
+    def stacktrace(preamble: String = " Calling trace:\n")(using Context): String = buildStacktrace(trace, preamble)
+
     def issue(using Context): Unit =
       report.warning(show, this.pos)
+  end Error
+
+  def buildStacktrace(trace: Seq[Tree], preamble: String)(using Context): String = if trace.isEmpty then "" else preamble + {
+    var lastLineNum = -1
+    var lines: mutable.ArrayBuffer[String] = new mutable.ArrayBuffer
+    trace.foreach { tree =>
+      val pos = tree.sourcePos
+      val prefix = "-> "
+      val line =
+        if pos.source.exists then
+          val loc = "[ " + pos.source.file.name + ":" + (pos.line + 1) + " ]"
+          val code = SyntaxHighlighting.highlight(pos.lineContent.trim.nn)
+          i"$code\t$loc"
+        else
+          tree.show
+      val positionMarkerLine =
+        if pos.exists && pos.source.exists then
+          positionMarker(pos)
+        else ""
 
-    def stacktrace(preamble: String = " Calling trace:\n")(using Context): String = if trace.isEmpty then "" else preamble + {
-      var lastLineNum = -1
-      var lines: mutable.ArrayBuffer[String] = new mutable.ArrayBuffer
-      trace.foreach { tree =>
-        val pos = tree.sourcePos
-        val prefix = "-> "
-        val line =
-          if pos.source.exists then
-            val loc = "[ " + pos.source.file.name + ":" + (pos.line + 1) + " ]"
-            val code = SyntaxHighlighting.highlight(pos.lineContent.trim.nn)
-            i"$code\t$loc"
-          else
-            tree.show
-        val positionMarkerLine =
-          if pos.exists && pos.source.exists then
-            positionMarker(pos)
-          else ""
-
-        // always use the more precise trace location
-        if lastLineNum == pos.line then
-          lines.dropRightInPlace(1)
-
-        lines += (prefix + line + "\n" + positionMarkerLine)
-
-        lastLineNum = pos.line
-      }
-      val sb = new StringBuilder
-      for line <- lines do sb.append(line)
-      sb.toString
+      // always use the more precise trace location
+      if lastLineNum == pos.line then
+        lines.dropRightInPlace(1)
+
+      lines += (prefix + line + "\n" + positionMarkerLine)
+
+      lastLineNum = pos.line
     }
+    val sb = new StringBuilder
+    for line <- lines do sb.append(line)
+    sb.toString
+  }
 
-    /** Used to underline source positions in the stack trace
-     *  pos.source must exist
-     */
-    private def positionMarker(pos: SourcePosition): String =
-      val trimmed = pos.lineContent.takeWhile(c => c.isWhitespace).length
-      val padding = pos.startColumnPadding.substring(trimmed).nn + "   "
-      val carets =
-        if (pos.startLine == pos.endLine)
-          "^" * math.max(1, pos.endColumn - pos.startColumn)
-        else "^"
+  /** Used to underline source positions in the stack trace
+   *  pos.source must exist
+   */
+  private def positionMarker(pos: SourcePosition): String =
+    val trimmed = pos.lineContent.takeWhile(c => c.isWhitespace).length
+    val padding = pos.startColumnPadding.substring(trimmed).nn + "   "
+    val carets =
+      if (pos.startLine == pos.endLine)
+        "^" * math.max(1, pos.endColumn - pos.startColumn)
+      else "^"
 
-      s"$padding$carets\n"
+    s"$padding$carets\n"
 
-    override def toString() = this.getClass.getName.nn
-  end Error
+  override def toString() = this.getClass.getName.nn
 
   /** Access non-initialized field */
   case class AccessNonInit(field: Symbol, trace: Seq[Tree]) extends Error:

compiler/src/dotty/tools/dotc/transform/init/Semantic.scala

@@ -652,7 +652,7 @@ object Semantic:
       value.promote(msg)
       value
 
-    def select(field: Symbol, needResolve: Boolean = true): Contextual[Value] = log("select " + field.show + ", this = " + value, printer, (_: Value).show) {
+    def select(field: Symbol, receiver: Type, needResolve: Boolean = true): Contextual[Value] = log("select " + field.show + ", this = " + value, printer, (_: Value).show) {
       if promoted.isCurrentObjectPromoted then Hot
       else value match {
         case Hot  =>
@@ -668,13 +668,11 @@ object Semantic:
           if target.is(Flags.Lazy) then
             val rhs = target.defTree.asInstanceOf[ValDef].rhs
             eval(rhs, ref, target.owner.asClass, cacheResult = true)
-          else
+          else if target.exists then
             val obj = ref.objekt
             if obj.hasField(target) then
               obj.field(target)
             else if ref.isInstanceOf[Warm] then
-              if !target.exists then
-                println("obj.klass = " + obj.klass.show + ", field = " + field.show)
               assert(obj.klass.isSubClass(target.owner))
               if target.is(Flags.ParamAccessor) then
                 // possible for trait parameters
@@ -693,13 +691,21 @@ object Semantic:
               val error = AccessNonInit(target, trace.toVector)
               reporter.report(error)
               Hot
+          else
+            if ref.klass.isSubClass(receiver.widenSingleton.classSymbol) then
+              report.error("Unexpected resolution failure: ref.klass = " + ref.klass.show + ", field = " + field.show + buildStacktrace(trace.toVector, "\n"))
+              Hot
+            else
+              // This is possible due to incorrect type cast.
+              // See tests/init/pos/Type.scala
+              Hot
 
         case fun: Fun =>
           report.error("[Internal error] unexpected tree in selecting a function, fun = " + fun.expr.show, fun.expr)
           Hot
 
         case RefSet(refs) =>
-          refs.map(_.select(field)).join
+          refs.map(_.select(field, receiver)).join
       }
     }
 
@@ -811,13 +817,21 @@ object Semantic:
                 val error = CallUnknown(target, trace.toVector)
                 reporter.report(error)
               Hot
-          else
+          else if target.exists then
             // method call resolves to a field
             val obj = ref.objekt
             if obj.hasField(target) then
               obj.field(target)
             else
-              value.select(target, needResolve = false)
+              value.select(target, receiver, needResolve = false)
+          else
+            if ref.klass.isSubClass(receiver.widenSingleton.classSymbol) then
+              report.error("Unexpected resolution failure: ref.klass = " + ref.klass.show + ", meth = " + meth.show + buildStacktrace(trace.toVector, "\n"))
+              Hot
+            else
+              // This is possible due to incorrect type cast.
+              // See tests/init/pos/Type.scala
+              Hot
 
         case Fun(body, thisV, klass) =>
           // meth == NoSymbol for poly functions
@@ -1126,12 +1140,12 @@ object Semantic:
               if member.is(Flags.Method, butNot = Flags.Accessor) then
                 withTrace(Trace.empty) {
                   val args = member.info.paramInfoss.flatten.map(_ => ArgInfo(Hot, Trace.empty))
-                  val res = warm.call(member, args, receiver = NoType, superType = NoType)
+                  val res = warm.call(member, args, receiver = warm.klass.typeRef, superType = NoType)
                   res.promote("Cannot prove that the return value of " + member.show + " is hot. Found = " + res.show + ". ")
                 }
               else
                 withTrace(Trace.empty) {
-                  val res = warm.select(member)
+                  val res = warm.select(member, receiver = warm.klass.typeRef)
                   res.promote("Cannot prove that the field " + member.show + " is hot. Found = " + res.show + ". ")
                 }
           end for
@@ -1346,7 +1360,7 @@ object Semantic:
               resolveThis(target, qual, current.asClass)
             }
           case _ =>
-            withTrace(trace2) { qual.select(expr.symbol) }
+            withTrace(trace2) { qual.select(expr.symbol, receiver = qualifier.tpe) }
 
       case _: This =>
         cases(expr.tpe, thisV, klass)
@@ -1468,7 +1482,7 @@ object Semantic:
         thisV.accessLocal(tmref, klass)
 
       case tmref: TermRef =>
-        cases(tmref.prefix, thisV, klass).select(tmref.symbol)
+        cases(tmref.prefix, thisV, klass).select(tmref.symbol, receiver = tmref.prefix)
 
       case tp @ ThisType(tref) =>
         val cls = tref.classSymbol.asClass

tests/init/pos/Type.scala

@@ -0,0 +1,21 @@
+class Type:
+  def underlyingType =
+    val isProxy = this.isInstanceOf[TypeProxy]
+    if (isProxy) this.asInstanceOf[TypeProxy].underlying
+    else NoType
+
+  def underlyingName =
+    val isProxy = this.isInstanceOf[TypeProxy]
+    if (isProxy) this.asInstanceOf[TypeProxy].name
+    else "<empty>"
+
+abstract class TypeProxy extends Type:
+  def underlying: Type = this
+  val name: String
+
+object NoType extends Type
+
+object Implicits:
+  object NoImplicits extends Type
+  println(NoImplicits)
+  val n = 10