fix #17836 (typed macro isNil for proc params) (#17841)

thanks @alaviss for the test

compiler/ast.nim

@@ -1171,6 +1171,7 @@ when defined(useNodeIds):
   var gNodeId: int
 
 proc newNode*(kind: TNodeKind): PNode =
+  ## new node with unknown line info, no type, and no children
   result = PNode(kind: kind, info: unknownLineInfo)
   when defined(useNodeIds):
     result.id = gNodeId
@@ -1180,6 +1181,7 @@ proc newNode*(kind: TNodeKind): PNode =
     inc gNodeId
 
 proc newNodeI*(kind: TNodeKind, info: TLineInfo): PNode =
+  ## new node with line info, no type, and no children
   result = PNode(kind: kind, info: info)
   when defined(useNodeIds):
     result.id = gNodeId
@@ -1189,6 +1191,7 @@ proc newNodeI*(kind: TNodeKind, info: TLineInfo): PNode =
     inc gNodeId
 
 proc newNodeI*(kind: TNodeKind, info: TLineInfo, children: int): PNode =
+  ## new node with line info, type, and children
   result = PNode(kind: kind, info: info)
   if children > 0:
     newSeq(result.sons, children)
@@ -1200,6 +1203,7 @@ proc newNodeI*(kind: TNodeKind, info: TLineInfo, children: int): PNode =
     inc gNodeId
 
 proc newNodeIT*(kind: TNodeKind, info: TLineInfo, typ: PType): PNode =
+  ## new node with line info, type, and no children
   result = newNode(kind)
   result.info = info
   result.typ = typ

compiler/vm.nim

@@ -1513,8 +1513,8 @@ proc rawExecute(c: PCtx, start: int, tos: PStackFrame): TFullReg =
         # reference with the value `nil`, so `isNil` should be false!
         (node.kind == nkNilLit and nfIsRef notin node.flags) or
         (not node.typ.isNil and node.typ.kind == tyProc and
-          node.typ.callConv == ccClosure and node[0].kind == nkNilLit and
-          node[1].kind == nkNilLit))
+          node.typ.callConv == ccClosure and node.safeLen > 0 and
+          node[0].kind == nkNilLit and node[1].kind == nkNilLit))
     of opcNBindSym:
       # cannot use this simple check
       # if dynamicBindSym notin c.config.features:

tests/macros/t17836.nim

@@ -0,0 +1,15 @@
+import macros
+
+# Ensure that `isNil` works in the typed macro context when pass procs.
+
+type
+  O = object
+    fn: proc(i: int): int
+
+var o: O
+
+macro typedBug(expr: typed) =
+  doAssert expr[1] != nil
+  doAssert not expr[1].isNil
+
+typedBug(o.fn)