SI-7345 More refactoring and documentation in Contexts

  - Use `firstError match {}` rather than `if (c.hasErrors) c.firstError ..`
  - Convert implementation comments to doc comments
  - Add new doc comments
  - Refactor `Context#make` for better readability.
  - Note a few TODOs.
  - Roughly delineate the internal structure of Contexts with comments.
  - Combine `mode` and `state` methods into `contextMode`.
  - Move `isNameInScope` closer to its compadres.
  - Improving alignment, tightening access.

1 files changed, 3 insertions, 4 deletions

diff --git a/src/compiler/scala/reflect/macros/runtime/Typers.scala b/src/compiler/scala/reflect/macros/runtime/Typers.scala
index 99b934787d..79833d155e 100644
--- a/src/compiler/scala/reflect/macros/runtime/Typers.scala
+++ b/src/compiler/scala/reflect/macros/runtime/Typers.scala
@@ -54,11 +54,10 @@ trait Typers {
     wrapper(universe.analyzer.inferImplicit(tree, pt, reportAmbiguous = true, isView = isView, context = context, saveAmbiguousDivergent = !silent, pos = pos)) match {
       case failure if failure.tree.isEmpty =>
         macroLogVerbose("implicit search has failed. to find out the reason, turn on -Xlog-implicits")
-        if (context.hasErrors) {
-          val err = context.firstError
-          throw new TypecheckException(err.errPos, err.errMsg)
+        context.firstError match {
+          case Some(err) => throw new TypecheckException(err.errPos, err.errMsg)
+          case None      => universe.EmptyTree
         }
-        universe.EmptyTree
       case success =>
         success.tree
     }