Fixes #1093.

compiler/vm.nim

@@ -354,6 +354,11 @@ template handleJmpBack() {.dirty.} =
       globalError(c.debug[pc], errTooManyIterations)
   dec(c.loopIterations)
 
+proc skipColon(n: PNode): PNode =
+  result = n
+  if n.kind == nkExprColonExpr:
+    result = n.sons[1]
+
 proc rawExecute(c: PCtx, start: int, tos: PStackFrame): TFullReg =
   var pc = start
   var tos = tos
@@ -454,7 +459,7 @@ proc rawExecute(c: PCtx, start: int, tos: PStackFrame): TFullReg =
       decodeBC(rkNode)
       let src = regs[rb].node
       if src.kind notin {nkEmpty..nkNilLit}:
-        let n = src.sons[rc]
+        let n = src.sons[rc].skipColon
         regs[ra].node = n
       else:
         stackTrace(c, tos, pc, errNilAccess)

compiler/vmgen.nim

@@ -316,14 +316,6 @@ proc genAndOr(c: PCtx; n: PNode; opc: TOpcode; dest: var TDest) =
   c.patch(L1)
 
 proc canonValue*(n: PNode): PNode =
-  if n.kind == nkExprColonExpr:
-    result = n.sons[1]
-  elif n.hasSubnodeWith(nkExprColonExpr):
-    result = n.copyNode
-    newSeq(result.sons, n.len)
-    for i in 0.. <n.len:
-      result.sons[i] = canonValue(n.sons[i])
-  else:
   result = n
 
 proc rawGenLiteral(c: PCtx; n: PNode): int =

tests/macros/texprcolonexpr.nim

@@ -0,0 +1,19 @@
+discard """
+  msg: '''
+Infix
+  Ident !"=>"
+  Call
+    Ident !"name"
+    Ident !"a"
+    ExprColonExpr
+      Ident !"b"
+      Ident !"cint"
+  NilLit nil
+'''
+"""
+import macros
+
+macro def(x: stmt): stmt {.immediate.} =
+  echo treeRepr(x)
+
+def name(a, b:cint) => nil