Print inlining positions in error messages

Error messages now print the inlined positions as well
as the position of the inlined call, recursively.

5 files changed, 42 insertions, 23 deletions

diff --git a/src/dotty/tools/dotc/core/Contexts.scala b/src/dotty/tools/dotc/core/Contexts.scala
index ea0ab95e6..f2a1fe53e 100644
--- a/src/dotty/tools/dotc/core/Contexts.scala
+++ b/src/dotty/tools/dotc/core/Contexts.scala
@@ -370,12 +370,8 @@ object Contexts {
     /** The current source file; will be derived from current
      *  compilation unit.
      */
-    def source: SourceFile = {
-      val file = Inliner.inlinedSource
-      if (file.exists) file
-      else if (compilationUnit == null) NoSource
-      else compilationUnit.source
-    }
+    def source: SourceFile =
+      if (compilationUnit == null) NoSource else compilationUnit.source
 
     /** Does current phase use an erased types interpretation? */
     def erasedTypes: Boolean = phase.erasedTypes
diff --git a/src/dotty/tools/dotc/core/Decorators.scala b/src/dotty/tools/dotc/core/Decorators.scala
index 387e7e466..fc546667d 100644
--- a/src/dotty/tools/dotc/core/Decorators.scala
+++ b/src/dotty/tools/dotc/core/Decorators.scala
@@ -7,6 +7,8 @@ import Contexts._, Names._, Phases._, printing.Texts._, printing.Printer, printi
 import util.Positions.Position, util.SourcePosition
 import collection.mutable.ListBuffer
 import dotty.tools.dotc.transform.TreeTransforms._
+import typer.Inliner
+import ast.tpd.Inlined
 import scala.language.implicitConversions
 import printing.Formatting._
 
@@ -148,8 +150,16 @@ object Decorators {
     }
   }
 
-  implicit def sourcePos(pos: Position)(implicit ctx: Context): SourcePosition =
-    ctx.source.atPos(pos)
+  implicit def sourcePos(pos: Position)(implicit ctx: Context): SourcePosition = {
+    def recur(inlineds: Stream[Inlined], pos: Position): SourcePosition = inlineds match {
+      case inlined #:: rest =>
+        Inliner.sourceFile(inlined).atPos(pos)
+          .withOuter(recur(rest, inlined.call.pos))
+      case empty =>
+        ctx.source.atPos(pos)
+    }
+    recur(Inliner.enclosingInlineds, pos)
+  }
 
   implicit class StringInterpolators(val sc: StringContext) extends AnyVal {
 
diff --git a/src/dotty/tools/dotc/reporting/ConsoleReporter.scala b/src/dotty/tools/dotc/reporting/ConsoleReporter.scala
index f35293d8d..deb772db5 100644
--- a/src/dotty/tools/dotc/reporting/ConsoleReporter.scala
+++ b/src/dotty/tools/dotc/reporting/ConsoleReporter.scala
@@ -21,11 +21,15 @@ class ConsoleReporter(
   /** maximal number of error messages to be printed */
   protected def ErrorLimit = 100
 
-  def printSourceLine(pos: SourcePosition) =
-    printMessage(pos.lineContent.stripLineEnd)
-
-  def printColumnMarker(pos: SourcePosition) =
-    if (pos.exists) { printMessage(" " * pos.column + "^") }
+  def printPos(pos: SourcePosition): Unit =
+    if (pos.exists) {
+      printMessage(pos.lineContent.stripLineEnd)
+      printMessage(" " * pos.column + "^")
+      if (pos.outer.exists) {
+        printMessage(s"\n... this location is in code that was inlined at ${pos.outer}:\n")
+        printPos(pos.outer)
+      }
+    }
 
   /** Prints the message. */
   def printMessage(msg: String): Unit = { writer.print(msg + "\n"); writer.flush() }
@@ -34,10 +38,7 @@ class ConsoleReporter(
   def printMessageAndPos(msg: String, pos: SourcePosition)(implicit ctx: Context): Unit = {
     val posStr = if (pos.exists) s"$pos: " else ""
     printMessage(posStr + msg)
-    if (pos.exists) {
-      printSourceLine(pos)
-      printColumnMarker(pos)
-    }
+    printPos(pos)
   }
 
   override def doReport(d: Diagnostic)(implicit ctx: Context): Unit = d match {
diff --git a/src/dotty/tools/dotc/typer/Inliner.scala b/src/dotty/tools/dotc/typer/Inliner.scala
index 28c725b33..8d25e3250 100644
--- a/src/dotty/tools/dotc/typer/Inliner.scala
+++ b/src/dotty/tools/dotc/typer/Inliner.scala
@@ -82,11 +82,19 @@ object Inliner {
   def inlineContext(tree: untpd.Inlined)(implicit ctx: Context): Context =
     ctx.fresh.setProperty(InlinedCall, tree)
 
-  def inlinedSource(implicit ctx: Context): SourceFile = ctx.property(InlinedCall) match {
-    case Some(inlined) =>
-      val file = inlined.call.symbol.sourceFile
-      if (file.exists) new SourceFile(file) else NoSource
-    case _ => NoSource
+  def enclosingInlineds(implicit ctx: Context): Stream[Inlined] =
+    ctx.property(InlinedCall) match {
+      case found @ Some(inlined) =>
+        inlined #::
+          enclosingInlineds(
+            ctx.outersIterator.dropWhile(_.property(InlinedCall) == found).next)
+      case _ =>
+        Stream.Empty
+    }
+
+  def sourceFile(inlined: Inlined)(implicit ctx: Context) = {
+    val file = inlined.call.symbol.sourceFile
+    if (file.exists) new SourceFile(file) else NoSource
   }
 }
 
diff --git a/src/dotty/tools/dotc/util/SourcePosition.scala b/src/dotty/tools/dotc/util/SourcePosition.scala
index 0b2b2aa0b..68a9b6403 100644
--- a/src/dotty/tools/dotc/util/SourcePosition.scala
+++ b/src/dotty/tools/dotc/util/SourcePosition.scala
@@ -5,7 +5,8 @@ package util
 import Positions.{Position, NoPosition}
 
 /** A source position is comprised of a position in a source file */
-case class SourcePosition(source: SourceFile, pos: Position) extends interfaces.SourcePosition {
+case class SourcePosition(source: SourceFile, pos: Position, outer: SourcePosition = NoSourcePosition)
+extends interfaces.SourcePosition {
   def exists = pos.exists
 
   def lineContent: String = source.lineContent(point)
@@ -24,6 +25,8 @@ case class SourcePosition(source: SourceFile, pos: Position) extends interfaces.
   def endLine: Int = source.offsetToLine(end)
   def endColumn: Int = source.column(end)
 
+  def withOuter(outer: SourcePosition) = new SourcePosition(source, pos, outer)
+
   override def toString =
     if (source.exists) s"${source.file}:${line + 1}"
     else s"(no source file, offset = ${pos.point})"
@@ -32,5 +35,6 @@ case class SourcePosition(source: SourceFile, pos: Position) extends interfaces.
 /** A sentinel for a non-existing source position */
 @sharable object NoSourcePosition extends SourcePosition(NoSource, NoPosition) {
   override def toString = "?"
+  override def withOuter(outer: SourcePosition) = outer
 }