better result injection

Author: arnetheduck

chronos/asyncmacro2.nim

@@ -113,6 +113,9 @@ proc asyncSingleProc(prc: NimNode): NimNode {.compileTime.} =
       raiseAssert("Unhandled async return type: " & $prc.kind)
 
   let subtypeIsVoid = baseType.eqIdent("void")
+  let returnTypeIsResult =
+    returnType.kind == nnkBracketExpr and baseType.kind == nnkBracketExpr and
+    (baseType[0].eqIdent("Result") or baseType[0].eqIdent("results.Result"))
 
   if prc.kind in {nnkProcDef, nnkLambda, nnkMethodDef, nnkDo}:
     let
@@ -147,11 +150,12 @@ proc asyncSingleProc(prc: NimNode): NimNode {.compileTime.} =
       # fix #13899, `defer` should not escape its original scope
       procBody = newStmtList(newTree(nnkBlockStmt, newEmptyNode(), procBody))
 
-      # Support `let x = ? await ...`
-      let ar = ident "assignResult?"
-      procBody.insert 0, quote do:
-        template `ar`(v: Result) =
-          `internalFutureSym`.complete(v)
+      if returnTypeIsResult:
+        # Support `let x = ? await ...`, but only if `Result` exists as a symbol
+        let ar = ident "assignResult?"
+        procBody.insert 0, quote do:
+            template `ar`(v: Result) =
+              `internalFutureSym`.complete(v)
 
       if not subtypeIsVoid:
         procBody.insert(0, newNimNode(nnkPragma).add(newIdentNode("push"),