fixes #7528

compiler/types.nim

@@ -1333,7 +1333,10 @@ proc computeSizeAux(typ: PType, a: var BiggestInt): BiggestInt =
     if typ.callConv == ccClosure: result = 2 * ptrSize
     else: result = ptrSize
     a = ptrSize
-  of tyNil, tyCString, tyString, tySequence, tyPtr, tyRef, tyVar, tyLent, tyOpenArray:
+  of tyString, tyNil:
+    result = ptrSize
+    a = result
+  of tyCString, tySequence, tyPtr, tyRef, tyVar, tyLent, tyOpenArray:
     let base = typ.lastSon
     if base == typ or (base.kind == tyTuple and base.size==szIllegalRecursion):
       result = szIllegalRecursion

tests/metatype/tautotypetrait.nim

@@ -0,0 +1,14 @@
+discard """
+  output: "(Field0: "string", Field1: "string")"
+"""
+
+# 7528
+import macros
+import typetraits
+
+macro bar*(n: untyped): typed =
+  result = newNimNode(nnkStmtList, n)
+  result.add(newCall("write", newIdentNode("stdout"), n))
+
+proc foo0[T](): auto = return (T.name, T.name)
+bar foo0[string]()