Fix #1604: print outer context if applicable

Author: felixmulder

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

@@ -62,6 +62,12 @@ class ConsoleReporter(
     s"$prefix|$whitespace${carets.show}"
   }
 
+  private 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 errorMsg(pos: SourcePosition, msg: String, offset: Int)(implicit ctx: Context) = {
     val leastWhitespace = msg.lines.foldLeft(Int.MaxValue) { (minPad, line) =>
       val lineLength = stripColor(line).length
@@ -101,7 +107,7 @@ class ConsoleReporter(
       val marker = columnMarker(pos, offset)
       val err = errorMsg(pos, msg.msg, offset)
 
-      printMessage((srcBefore ::: marker :: err :: srcAfter).mkString("\n"))
+      printMessage((srcBefore ::: marker :: err :: outer(pos, " " * (offset - 1)) ::: srcAfter).mkString("\n"))
     } else printMessage(msg.msg)
     true
   }

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 = {