Fix semantic pass with borrowed magic procs (#8945)

Reported by pqflx3 on the forum.

compiler/semstmts.nim

@@ -1173,6 +1173,9 @@ proc semBorrow(c: PContext, n: PNode, s: PSym) =
   if b != nil:
     # store the alias:
     n.sons[bodyPos] = newSymNode(b)
+    # Carry over the original symbol magic, this is necessary in order to ensure
+    # the semantic pass is correct
+    s.magic = b.magic
   else:
     localError(c.config, n.info, errNoSymbolToBorrowFromFound)
 

tests/ccgbugs/tborrowmagic.nim

@@ -0,0 +1,8 @@
+type
+  Bytes = distinct seq[byte]
+
+proc add(x: var Bytes; b: byte) {.borrow.}
+var x = @[].Bytes
+x.add(42)
+let base = cast[seq[byte]](x)
+doAssert base.len == 1 and base[0] == 42