fixes #22148; std/memfiles.memSlices nesting now fails with memory sa… (#22154)

* fixes #22148; std/memfiles.memSlices nesting now fails with memory safety capture violation

* adds a test case

compiler/transf.nim

@@ -326,7 +326,7 @@ proc introduceNewLocalVars(c: PTransf, n: PNode): PNode =
     return n
   of nkProcDef: # todo optimize nosideeffects?
     result = newTransNode(n)
-    let x = freshVar(c, n[namePos].sym)
+    let x = newSymNode(copySym(n[namePos].sym, c.idgen))
     idNodeTablePut(c.transCon.mapping, n[namePos].sym, x)
     result[namePos] = x # we have to copy proc definitions for iters
     for i in 1..<n.len:

tests/iter/t22148.nim

@@ -0,0 +1,15 @@
+discard """
+  action: compile
+"""
+
+import std/memfiles
+
+# bug #22148
+proc make*(input: string) =
+  var inp = memfiles.open(input)
+  for line in memSlices(inp):
+    let lineF = MemFile(mem: line.data, size: line.size)
+    for word in memSlices(lineF, ','):
+      discard
+
+make("") # Must call to trigger