generalizes macroExpand

Changes macroExpand to accommodate expansion schemes different from the
currently supported one.

As a bonus, which follows clarification of the macro expansion logic,
this refactoring fixes suppression of macro expansions, which
previously didn't work with delayed expansion.

1 files changed, 10 insertions, 3 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/ContextErrors.scala b/src/compiler/scala/tools/nsc/typechecker/ContextErrors.scala
index df78f8a05d..2d4054e93b 100644
--- a/src/compiler/scala/tools/nsc/typechecker/ContextErrors.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/ContextErrors.scala
@@ -676,6 +676,10 @@ trait ContextErrors {
         NormalTypeError(expandee, "too many argument lists for " + fun)
       }
 
+      def MacroInvalidExpansionError(expandee: Tree, role: String, allowedExpansions: String) = {
+        issueNormalTypeError(expandee, s"macro in $role role can only expand into $allowedExpansions")
+      }
+
       // same reason as for MacroBodyTypecheckException
       case object MacroExpansionException extends Exception with scala.util.control.ControlThrowable
 
@@ -757,13 +761,16 @@ trait ContextErrors {
         macroExpansionError(expandee, template(sym.name.nameKind).format(sym.name + " " + sym.origin, forgotten))
       }
 
-      def MacroExpansionIsNotExprError(expandee: Tree, expanded: Any) =
+      def MacroExpansionHasInvalidTypeError(expandee: Tree, expanded: Any) = {
+        val expected = "expr"
+        val isPathMismatch = expanded != null && expanded.isInstanceOf[scala.reflect.api.Exprs#Expr[_]]
         macroExpansionError(expandee,
-          "macro must return a compiler-specific expr; returned value is " + (
+          s"macro must return a compiler-specific $expected; returned value is " + (
             if (expanded == null) "null"
-            else if (expanded.isInstanceOf[Expr[_]]) " Expr, but it doesn't belong to this compiler's universe"
+            else if (isPathMismatch) s" $expected, but it doesn't belong to this compiler"
             else " of " + expanded.getClass
         ))
+      }
 
       def MacroImplementationNotFoundError(expandee: Tree) =
         macroExpansionError(expandee,