overloading resolution for getAst; breaking change

tests/macros/tdumpast.nim

@@ -2,13 +2,13 @@
 
 import macros
 
-template plus(a, b: expr): expr {.dirty} =
+template plus(a, b: untyped): untyped {.dirty} =
   a + b
 
-macro call(e: expr): expr =
+macro call(e: untyped): untyped =
   result = newCall("foo", newStrLitNode("bar"))
 
-macro dumpAST(n: stmt): stmt {.immediate.} =
+macro dumpAST(n: untyped): untyped =
   # dump AST as a side-effect and return the inner node
   let n = callsite()
   echo n.lispRepr
@@ -17,7 +17,7 @@ macro dumpAST(n: stmt): stmt {.immediate.} =
   var plusAst = getAst(plus(1, 2))
   echo plusAst.lispRepr
 
-  var callAst = getAst(call())
+  var callAst = getAst(call(4))
   echo callAst.lispRepr
 
   var e = parseExpr("foo(bar + baz)")