1//===- TemplateArgumentHasher.h - Hash Template Arguments -------*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9#include "clang/AST/TemplateBase.h"
10
11namespace clang {
12namespace serialization {
13
14/// Calculate a stable hash value for template arguments. We guarantee that
15/// the same template arguments must have the same hashed values. But we don't
16/// guarantee that the template arguments with the same hashed value are the
17/// same template arguments.
18///
19/// ODR hashing may not be the best mechanism to hash the template
20/// arguments. ODR hashing is (or perhaps, should be) about determining whether
21/// two things are spelled the same way and have the same meaning (as required
22/// by the C++ ODR), whereas what we want here is whether they have the same
23/// meaning regardless of spelling. Maybe we can get away with reusing ODR
24/// hashing anyway, on the basis that any canonical, non-dependent template
25/// argument should have the same (invented) spelling in every translation
26/// unit, but it is not sure that's true in all cases. There may still be cases
27/// where the canonical type includes some aspect of "whatever we saw first",
28/// in which case the ODR hash can differ across translation units for
29/// non-dependent, canonical template arguments that are spelled differently
30/// but have the same meaning. But it is not easy to raise examples.
31unsigned StableHashForTemplateArguments(llvm::ArrayRef<TemplateArgument> Args);
32
33} // namespace serialization
34} // namespace clang
35