[clang-tools-extra] [clangd] [C++20] [Modules] Introduce initial support for C++20 Modules (PR #66462)

[Pol M via cfe-commits]

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@@ -0,0 +1,86 @@
+//===----------------- PrerequisiteModules.h ---------------------*- C++-*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANGD_PREREQUISITEMODULES_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANGD_PREREQUISITEMODULES_H
+
+#include "Compiler.h"
+#include "support/Path.h"
+
+#include "clang/Lex/HeaderSearchOptions.h"
+
+#include "llvm/ADT/StringSet.h"
+
+namespace clang {
+namespace clangd {
+
+class ModulesBuilder;
+
+/// Store all the needed module files information to parse a single
+/// source file. e.g.,
+///
+///   ```
+///   // a.cppm
+///   export module a;
+///
+///   // b.cppm
+///   export module b;
+///   import a;
+///
+///   // c.cppm
+///   export module c;
+///   import a;
+///   ```
+///
+/// For the source file `c.cppm`, an instance of the class will store
+/// the module files for `a.cppm` and `b.cppm`. But the module file for `c.cppm`
+/// won't be stored. Since it is not needed to parse `c.cppm`.
+///
+/// Users should only get PrerequisiteModules from
+/// `ModulesBuilder::buildPrerequisiteModulesFor(...)`.
+///
+/// Users can detect whether the PrerequisiteModules is still up to date by
+/// calling the `canReuse()` member function.
+///
+/// The users should call `adjustHeaderSearchOptions(...)` to update the
+/// compilation commands to select the built module files first. Before calling
+/// `adjustHeaderSearchOptions()`, users should call `canReuse()` first to check
+/// if all the stored module files are valid. In case they are not valid,
+/// users should call `ModulesBuilder::buildPrerequisiteModulesFor(...)` again
+/// to get the new PrerequisiteModules.
+class PrerequisiteModules {
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Destroyerrrocket wrote:

And you'll need to define a virtual destructor here as well

https://github.com/llvm/llvm-project/pull/66462