Added expandMacros macro

1 files changed, 24 insertions, 0 deletions

diff --git a/lib/core/macros.nim b/lib/core/macros.nim
index 19452b4a8..af346e2b3 100644
--- a/lib/core/macros.nim
+++ b/lib/core/macros.nim
@@ -890,6 +890,30 @@ proc boolVal*(n: NimNode): bool {.compileTime, noSideEffect.} =
   if n.kind == nnkIntLit: n.intVal != 0
   else: n == bindSym"true" # hacky solution for now
 
+macro expandMacros*(body: stmt): untyped =
+  ## Expands one level of macro - useful for debugging.
+  ## Can be used to inspect what happens when a macro call is expanded,
+  ## without altering its result.
+  ##
+  ## For instance,
+  ##
+  ## .. code-block:: nim
+  ##   import future, macros
+  ##
+  ##   let
+  ##     x = 10
+  ##     y = 20
+  ##   expandMacros:
+  ##     dump(x + y)
+  ##
+  ## will actually dump `x + y`, but at the same time will print at
+  ## compile time the expansion of the ``dump`` macro, which in this
+  ## case is ``debugEcho ["x + y", " = ", x + y]``.
+  template inner(x: untyped): untyped = x
+
+  result = getAst(inner(body))
+  echo result.toStrLit
+
 when not defined(booting):
   template emit*(e: static[string]): untyped {.deprecated.} =
     ## accepts a single string argument and treats it as nim code