Fix #1604: print outer context if applicable

Author: felixmulder

src/dotty/tools/dotc/reporting/MessageRendering.scala

@@ -15,6 +15,12 @@ trait MessageRendering {
   def stripColor(str: String): String =
     str.replaceAll("\u001B\\[[;\\d]*m", "")
 
+  def outer(pos: SourcePosition, prefix: String)(implicit ctx: Context): List[String] =
+    if (pos.outer.exists) {
+       s"$prefix| This location is in code that was inlined at ${pos.outer}" ::
+       outer(pos.outer, prefix)
+    } else Nil
+
   def sourceLines(pos: SourcePosition)(implicit ctx: Context): (List[String], List[String], Int) = {
     var maxLen = Int.MinValue
     def render(xs: List[Int]) =
@@ -92,7 +98,7 @@ trait MessageRendering {
       val (srcBefore, srcAfter, offset) = sourceLines(pos)
       val marker = columnMarker(pos, offset)
       val err = errorMsg(pos, msg.msg, offset)
-      sb.append((srcBefore ::: marker :: err :: srcAfter).mkString("\n"))
+      sb.append((srcBefore ::: marker :: err :: outer(pos, " " * (offset - 1)) ::: srcAfter).mkString("\n"))
     } else sb.append(msg.msg)
     sb.toString
   }

src/dotty/tools/dotc/typer/Inliner.scala

@@ -236,10 +236,12 @@ object Inliner {
   def inlineCall(tree: Tree, pt: Type)(implicit ctx: Context): Tree =
     if (enclosingInlineds.length < ctx.settings.xmaxInlines.value)
       new Inliner(tree, bodyToInline(tree.symbol)).inlined(pt)
-    else errorTree(tree,
-      i"""Maximal number of successive inlines (${ctx.settings.xmaxInlines.value}) exceeded,
-                   | Maybe this is caused by a recursive inline method?
-                   | You can use -Xmax:inlines to change the limit.""")
+    else errorTree(
+      tree,
+      i"""|Maximal number of successive inlines (${ctx.settings.xmaxInlines.value}) exceeded,
+          |Maybe this is caused by a recursive inline method?
+          |You can use -Xmax:inlines to change the limit."""
+    )
 
   /** Replace `Inlined` node by a block that contains its bindings and expansion */
   def dropInlined(inlined: tpd.Inlined)(implicit ctx: Context): Tree = {