Commit Graph

372 Commits

Author SHA1 Message Date
Corentin Jabot aee76cb59c [Clang] Add support for Unicode identifiers (UAX31) in C2x mode.
This implements
N2836 Identifier Syntax using Unicode Standard Annex 31.

The feature was already implemented for C++,
and the semantics are the same.

Unlike C++ there was, afaict, no decision to
backport the feature in older languages mode,
so C17 and earlier are not modified and the
code point tables for these language modes are conserved.

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D130416
2022-07-23 14:08:08 +02:00
Corentin Jabot 6882ca9aff [Clang] Adjust extension warnings for delimited sequences
WG21 approved delimited escape sequences and named escape
sequences.
Adjust the extension warnings accordingly, and update
the release notes.

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D129664
2022-07-14 07:50:58 +02:00
Corentin Jabot d4892a168f [Clang] Add a warning on invalid UTF-8 in comments.
Introduce an off-by default `-Winvalid-utf8` warning
that detects invalid UTF-8 code units sequences in comments.

Invalid UTF-8 in other places is already diagnosed,
as that cannot appear in identifiers and other grammar constructs.

The warning is off by default as its likely to be somewhat disruptive
otherwise.

This warning allows clang to conform to the yet-to be approved WG21
"P2295R5 Support for UTF-8 as a portable source file encoding"
paper.

Reviewed By: aaron.ballman, #clang-language-wg

Differential Revision: https://reviews.llvm.org/D128059
2022-07-13 10:19:26 +02:00
Jonas Devlieghere a262f4dbd7 Revert "[Clang] Add a warning on invalid UTF-8 in comments."
This reverts commit cc309721d2 because it
breaks the following tests on GreenDragon:

  TestDataFormatterObjCCF.py
  TestDataFormatterObjCExpr.py
  TestDataFormatterObjCKVO.py
  TestDataFormatterObjCNSBundle.py
  TestDataFormatterObjCNSData.py
  TestDataFormatterObjCNSError.py
  TestDataFormatterObjCNSNumber.py
  TestDataFormatterObjCNSURL.py
  TestDataFormatterObjCPlain.py
  TestDataFormatterObjNSException.py

https://green.lab.llvm.org/green/view/LLDB/job/lldb-cmake/45288/
2022-07-12 15:22:29 -07:00
Corentin Jabot cc309721d2 [Clang] Add a warning on invalid UTF-8 in comments.
Introduce an off-by default `-Winvalid-utf8` warning
that detects invalid UTF-8 code units sequences in comments.

Invalid UTF-8 in other places is already diagnosed,
as that cannot appear in identifiers and other grammar constructs.

The warning is off by default as its likely to be somewhat disruptive
otherwise.

This warning allows clang to conform to the yet-to be approved WG21
"P2295R5 Support for UTF-8 as a portable source file encoding"
paper.

Reviewed By: aaron.ballman, #clang-language-wg

Differential Revision: https://reviews.llvm.org/D128059
2022-07-12 14:34:30 +02:00
Corentin Jabot 50416e5454 Revert "[Clang] Add a warning on invalid UTF-8 in comments."
It is probable thart this change crashes on the powerpc bots.

This reverts commit 355532a149.
2022-07-09 17:18:35 +02:00
Corentin Jabot 355532a149 [Clang] Add a warning on invalid UTF-8 in comments.
Introduce an off-by default `-Winvalid-utf8` warning
that detects invalid UTF-8 code units sequences in comments.

Invalid UTF-8 in other places is already diagnosed,
as that cannot appear in identifiers and other grammar constructs.

The warning is off by default as its likely to be somewhat disruptive
otherwise.

This warning allows clang to conform to the yet-to be approved WG21
"P2295R5 Support for UTF-8 as a portable source file encoding"
paper.

Reviewed By: aaron.ballman, #clang-language-wg

Differential Revision: https://reviews.llvm.org/D128059
2022-07-09 11:26:45 +02:00
Nico Weber e9fe20dab3 Revert "[Clang] Add a warning on invalid UTF-8 in comments."
This reverts commit 4174f0ca61.

Also revert follow-up "[Clang] Fix invalid utf-8 detection"
This reverts commit bf45e27a67.

The second commit broke tests, see comments on
https://reviews.llvm.org/D129223, and it sounds like the first
commit isn't valid without the second one. So reverting both for now.
2022-07-06 22:51:52 +02:00
Corentin Jabot 4174f0ca61 [Clang] Add a warning on invalid UTF-8 in comments.
Introduce an off-by default `-Winvalid-utf8` warning
that detects invalid UTF-8 code units sequences in comments.

Invalid UTF-8 in other places is already diagnosed,
as that cannot appear in identifiers and other grammar constructs.

The warning is off by default as its likely to be somewhat disruptive
otherwise.

This warning allows clang to conform to the yet-to be approved WG21
"P2295R5 Support for UTF-8 as a portable source file encoding"
paper.

Reviewed By: aaron.ballman, #clang-language-wg

Differential Revision: https://reviews.llvm.org/D128059
2022-07-06 21:18:29 +02:00
Corentin Jabot fb06dd3e8c Revert "[Clang] Add a warning on invalid UTF-8 in comments."
Reverting while I investigate build failures

This reverts commit e3dc56805f.
2022-07-06 19:45:12 +02:00
Corentin Jabot e3dc56805f [Clang] Add a warning on invalid UTF-8 in comments.
Introduce an off-by default `-Winvalid-utf8` warning
that detects invalid UTF-8 code units sequences in comments.

Invalid UTF-8 in other places is already diagnosed,
as that cannot appear in identifiers and other grammar constructs.

The warning is off by default as its likely to be somewhat disruptive
otherwise.

This warning allows clang to conform to the yet-to be approved WG21
"P2295R5 Support for UTF-8 as a portable source file encoding"
paper.

Reviewed By: aaron.ballman, #clang-language-wg

Differential Revision: https://reviews.llvm.org/D128059
2022-07-06 17:59:44 +02:00
Argyrios Kyrtzidis c68b8c84eb [Lex] Make sure to notify `MultipleIncludeOpt` for "read tokens" during fast dependency directive lexing
Otherwise a header may be erroneously marked as having a header macro guard and won't get re-included.

Differential Revision: https://reviews.llvm.org/D128772
2022-06-29 15:50:16 -07:00
Corentin Jabot c92056d038 [Clang][C++23] P2071 Named universal character escapes
Implements [[ https://wg21.link/p2071r1  | P2071 Named Universal Character Escapes ]] - as an extension in all language mode, the patch  not warn in c++23 mode will be done later once this paper is plenary approved (in July).

We add

 * A code generator that transforms `UnicodeData.txt` and `NameAliases.txt` to a space efficient data structure that can be queried in `O(NameLength)`
 * A set of functions in `Unicode.h` to query that data, including

   * A function to find an exact match of a given Unicode character name
   * A function to perform a loose (ignoring case, space, underscore, medial hyphen) matching
   * A function returning the best matching codepoint for a given string per edit distance

 * Support of `\N{}` escape sequences in String and character Literals, with loose and typos diagnostics/fixits
 * Support of `\N{}` as UCN with loose matching diagnostics/fixits.

Loose matching is considered an error to match closely the semantics of P2071.

The generated data contributes to 280kB of data to the binaries.

`UnicodeData.txt` and `NameAliases.txt`  are not committed to the repository in this patch, and regenerating the data is a manual process.

Reviewed By: tahonermann

Differential Revision: https://reviews.llvm.org/D123064
2022-06-25 19:03:33 +02:00
Argyrios Kyrtzidis fad6e37995 [Lex] Fix crash during dependency scanning while skipping an unmatched `#if` 2022-05-27 23:59:30 -07:00
Argyrios Kyrtzidis b4c83a13f6 [Tooling/DependencyScanning & Preprocessor] Refactor dependency scanning to produce pre-lexed preprocessor directive tokens, instead of minimized sources
This is a commit with the following changes:

* Remove `ExcludedPreprocessorDirectiveSkipMapping` and related functionality

Removes `ExcludedPreprocessorDirectiveSkipMapping`; its intended benefit for fast skipping of excluded directived blocks
will be superseded by a follow-up patch in the series that will use dependency scanning lexing for the same purpose.

* Refactor dependency scanning to produce pre-lexed preprocessor directive tokens, instead of minimized sources

Replaces the "source minimization" mechanism with a mechanism that produces lexed dependency directives tokens.

* Make the special lexing for dependency scanning a first-class feature of the `Preprocessor` and `Lexer`

This is bringing the following benefits:

    * Full access to the preprocessor state during dependency scanning. E.g. a component can see what includes were taken and where they were located in the actual sources.
    * Improved performance for dependency scanning. Measurements with a release+thin-LTO build shows ~ -11% reduction in wall time.
    * Opportunity to use dependency scanning lexing to speed-up skipping of excluded conditional blocks during normal preprocessing (as follow-up, not part of this patch).

For normal preprocessing measurements show differences are below the noise level.

Since, after this change, we don't minimize sources and pass them in place of the real sources, `DependencyScanningFilesystem` is not technically necessary, but it has valuable performance benefits for caching file `stat`s along with the results of scanning the sources. So the setup of using the `DependencyScanningFilesystem` during a dependency scan remains.

Differential Revision: https://reviews.llvm.org/D125486
Differential Revision: https://reviews.llvm.org/D125487
Differential Revision: https://reviews.llvm.org/D125488
2022-05-26 12:50:06 -07:00
Christopher Di Bella e9a902c7f7 Revert "Revert "Revert "[clang][pp] adds '#pragma include_instead'"""
> Includes regression test for problem noted by @hans.
> is reverts commit 973de71.
>
> Differential Revision: https://reviews.llvm.org/D106898

Feature implemented as-is is fairly expensive and hasn't been used by
libc++. A potential reimplementation is possible if libc++ become
interested in this feature again.

Differential Revision: https://reviews.llvm.org/D123885
2022-04-22 16:37:20 +00:00
Timm Bäder 33ec653055 [clang][lexer] Allow u8 character literal prefixes in C2x
Implement N2418 for C2x.

Differential Revision: https://reviews.llvm.org/D119221
2022-04-19 09:57:51 +02:00
Dawid Jurczak d813116c9d [NFC][Lexer] Remove getLangOpts function from Lexer
Given that there is only one external user of Lexer::getLangOpts
we can remove getter entirely without much pain.

Differential Revision: https://reviews.llvm.org/D120404
2022-03-02 11:17:05 +01:00
Dawid Jurczak a64d3c602f [NFC][Lexer] Make Lexer::LangOpts const reference
This change can be seen as code cleanup but motivation is more performance related.
While browsing perf reports captured during Linux build we can notice unusual portion of instructions executed in std::vector<std::string> copy constructor like:

0.59%     0.58%  clang-14    clang-14      [.] std::vector<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >,
                                                                std::allocator<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > >::vector

or even:

1.42%     0.26%  clang    clang-14             [.] clang::LangOptions::LangOptions
       |
        --1.16%--clang::LangOptions::LangOptions
                  |
                   --0.74%--std::vector<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >,
                            std::allocator<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > >::vector

After more digging we can see that relevant LangOptions std::vector members (*Files, ModuleFeatures and NoBuiltinFuncs)
are constructed when Lexer::LangOpts field is initialized on list:

Lexer::Lexer(..., const LangOptions &langOpts, ...)
            : ..., LangOpts(langOpts),

Since LangOptions copy constructor is called by Lexer(..., const LangOptions &LangOpts,...) and local Lexer objects are created thousands times
(in Lexer::getRawToken, Preprocessor::EnterSourceFile and more) during single module processing in frontend it makes std::vector copy constructors surprisingly hot.

Unfortunately even though in current Lexer implementation mentioned std::vector members are unused and most of time empty,
no compiler is smart enough to optimize their std::vector copy constructors out (take a look at test assembly): https://godbolt.org/z/hdoxPfMYY even with LTO enabled.
However there is simple way to fix this. Since Lexer doesn't access *Files, ModuleFeatures, NoBuiltinFuncs and any other LangOptions fields (but only LangOptionsBase)
we can simply get rid of redundant copy constructor assembly by changing LangOpts type to more appropriate const LangOptions reference: https://godbolt.org/z/fP7de9176

Additionally we need to store LineComment outside LangOpts because it's written in SkipLineComment function.
Also FormatTokenLexer need to be adjusted a bit to avoid lifetime issues related to passing local LangOpts reference to Lexer.

After this change I can see more than 1% speedup in some of my microbenchmarks when using Clang release binary built with LTO.
For Linux build gains are not so significant but still nice at the level of -0.4%/-0.5% instructions drop.

Differential Revision: https://reviews.llvm.org/D120334
2022-02-28 15:42:19 +01:00
Dawid Jurczak fbe38a784e [NFC][Lexer] Make access to LangOpts more consistent
Before this change without any good reason Lexer::LangOpts is sometimes accessed by getter and another time read directly in Lexer functions.
Since getLangOpts is a bit more verbose prefer direct access to LangOpts member when possible.

Differential Revision: https://reviews.llvm.org/D120333
2022-02-23 12:46:13 +01:00
Kadir Cetinkaya ff77071a4d
[clang][Lexer] Make raw and normal lexer behave the same for line comments
Normally there are heruistics in lexer to treat `//*` specially in
language modes that don't have line comments (to emit `/`). Unfortunately this
only applied to the first occurence of a line comment inside the file, as the
subsequent line comments were treated as if language had support for them.

This unfortunately only holds in normal lexing mode, as in raw mode all
occurences of line comments received this treatment, which created discrepancies
when comparing expanded and spelled tokens.

The proper fix would be to just make sure we treat all the line comments with a
subsequent `*` the same way, but it would imply breaking some code that's
accepted by clang today. So instead we introduce the same bug into raw lexing
mode.

Fixes https://github.com/clangd/clangd/issues/1003.

Differential Revision: https://reviews.llvm.org/D118471
2022-01-31 16:15:16 +01:00
Kazu Hirata 298367ee6e [clang] Use nullptr instead of 0 or NULL (NFC)
Identified with modernize-use-nullptr.
2021-12-29 08:34:20 -08:00
Jan Svoboda 197576c409 [clang][lex] Refactor check for the first file include
This patch refactors the code that checks whether a file has just been included for the first time.

The `HeaderSearch::FirstTimeLexingFile` function is removed and the information is threaded to the original call site from `HeaderSearch::ShouldEnterIncludeFile`. This will make it possible to avoid tracking the number of includes in a follow up patch.

Depends on D114092.

Reviewed By: dexonsmith

Differential Revision: https://reviews.llvm.org/D114093
2021-11-18 13:01:07 +01:00
Corentin Jabot 274adcb866 Implement delimited escape sequences.
\x{XXXX} \u{XXXX} and \o{OOOO} are accepted in all languages mode
in characters and string literals.

This is a feature proposed for both C++ (P2290R1) and C (N2785). The
papers have been seen by both committees but are not yet adopted into
either standard. However, they do have support from both committees.
2021-09-15 09:54:49 -04:00
Corentin Jabot 601102d282 Cleanup identifier parsing; NFC
Rename methods to clearly signal when they only deal with ASCII,
simplify the parsing of identifier, and use start/continue instead of
head/body for consistency with Unicode terminology.
2021-09-14 09:12:22 -04:00
Corentin Jabot 2715c4da50 Do not emit diagnostics for invalid unicode characters in preprocessing mode
This amends 4e80636db7 with a fix for
https://lab.llvm.org/buildbot/#/builders/139/builds/8943
2021-08-18 09:12:36 -04:00
Corentin Jabot 4e80636db7 Implement P1949
This adds the Unicode 13 data for XID_Start and XID_Continue.
The definition of valid identifier is changed in all C++ modes
as P1949 (https://wg21.link/p1949) was accepted by WG21 as a defect
report.
2021-08-18 07:33:14 -04:00
Christopher Di Bella 0871954197 Revert "Revert "[clang][pp] adds '#pragma include_instead'""
Includes regression test for problem noted by @hans.
This reverts commit 973de71856.

Differential Revision: https://reviews.llvm.org/D106898
2021-07-29 19:21:43 +00:00
Hans Wennborg 973de71856 Revert "[clang][pp] adds '#pragma include_instead'"
> `#pragma clang include_instead(<header>)` is a pragma that can be used
> by system headers (and only system headers) to indicate to a tool that
> the file containing said pragma is an implementation-detail header and
> should not be directly included by user code.
>
> The library alternative is very messy code that can be seen in the first
> diff of D106124, and we'd rather avoid that with something more
> universal.
>
> This patch takes the first step by warning a user when they include a
> detail header in their code, and suggests alternative headers that the
> user should include instead. Future work will involve adding a fixit to
> automate the process, as well as cleaning up modules diagnostics to not
> suggest said detail headers. Other tools, such as clangd can also take
> advantage of this pragma to add the correct user headers.
>
> Differential Revision: https://reviews.llvm.org/D106394

This caused compiler crashes in Chromium builds involving PCH and an include
directive with macro expansion, when Token::getLiteralData() returned null. See
the code review for details.

This reverts commit e8a64e5491.
2021-07-27 17:29:48 +02:00
Christopher Di Bella e8a64e5491 [clang][pp] adds '#pragma include_instead'
`#pragma clang include_instead(<header>)` is a pragma that can be used
by system headers (and only system headers) to indicate to a tool that
the file containing said pragma is an implementation-detail header and
should not be directly included by user code.

The library alternative is very messy code that can be seen in the first
diff of D106124, and we'd rather avoid that with something more
universal.

This patch takes the first step by warning a user when they include a
detail header in their code, and suggests alternative headers that the
user should include instead. Future work will involve adding a fixit to
automate the process, as well as cleaning up modules diagnostics to not
suggest said detail headers. Other tools, such as clangd can also take
advantage of this pragma to add the correct user headers.

Differential Revision: https://reviews.llvm.org/D106394
2021-07-26 16:07:45 +00:00
Simon Tatham 21401a7262 [clang] Introduce SourceLocation::[U]IntTy typedefs.
This is part of a patch series working towards the ability to make
SourceLocation into a 64-bit type to handle larger translation units.

NFC: this patch introduces typedefs for the integer type used by
SourceLocation and makes all the boring changes to use the typedefs
everywhere, but for the moment, they are unconditionally defined to
uint32_t.

Patch originally by Mikhail Maltsev.

Reviewed By: tmatheson

Differential Revision: https://reviews.llvm.org/D105492
2021-07-21 10:45:46 +01:00
Sam McCall fd22785054 [Lex] Consider a PCH header-guarded even with #endif truncated
This seems to be a more useful behavior for tools that use preambles.
I believe it doesn't affect real compiles: the PCH is only included once
when used, and recursive inclusion of the main-file *within* the PCH
isn't supported in any case.

Differential Revision: https://reviews.llvm.org/D106204
2021-07-20 14:25:36 +02:00
Yitzhak Mandelbaum 93dc73b1e0 [Lexer] Fix bug in `makeFileCharRange` called on split tokens.
When the end loc of the specified range is a split token, `makeFileCharRange`
does not process it correctly.  This patch adds proper support for split tokens.

Differential Revision: https://reviews.llvm.org/D105365
2021-07-14 14:36:31 +00:00
Aaron Ballman 8edd3464af Add support for #elifdef and #elifndef
WG14 adopted N2645 and WG21 EWG has accepted P2334 in principle (still
subject to full EWG vote + CWG review + plenary vote), which add
support for #elifdef as shorthand for #elif defined and #elifndef as
shorthand for #elif !defined. This patch adds support for the new
preprocessor directives.
2021-05-27 08:57:47 -04:00
Richard Smith de6164ec4d PR50456: Properly handle multiple escaped newlines in a '*/'. 2021-05-24 16:21:03 -07:00
serge-sans-paille 9628cb1fee [NFC] Use higher level constructs to check for whitespace/newlines in the lexer
It turns out that according to valgrind and perf, it's also slightly faster.

Differential Revision: https://reviews.llvm.org/D98637
2021-03-15 18:27:19 +01:00
Aaron Ballman e448310059 Add support for digit separators in C2x.
WG14 adopted N2626 at the meetings this week. This commit adds support
for using ' as a digit separator in a numeric literal which is
compatible with the C++ feature.
2021-03-12 07:21:03 -05:00
Duncan P. N. Exon Smith b3eff6b7bb Lexer: Update the Lexer to use MemoryBufferRef, NFC
Update `Lexer` / `Lexer::Lexer` to use `MemoryBufferRef` instead of
`MemoryBuffer*`. Callers that were acquiring a `MemoryBuffer*` via
`SourceManager::getBuffer` were updated, such that if they checked
`Invalid` they use `getBufferOrNone` and otherwise `getBufferOrFake`.

Differential Revision: https://reviews.llvm.org/D89398
2020-10-19 19:10:21 -04:00
Zequan Wu 9caa3fbe03 [Coverage] Add empty line regions to SkippedRegions
Differential Revision: https://reviews.llvm.org/D84988
2020-09-21 12:42:53 -07:00
Eric Christopher 1f593f46f3 [AST/Lex/Parse/Sema] As part of using inclusive language within
the llvm project, migrate away from the use of blacklist and whitelist.
2020-06-20 01:15:32 -07:00
Aaron Ballman 1b3f1f4436 Rename warning identifiers from cxx2a to cxx20; NFC. 2020-04-22 14:31:13 -04:00
Aaron Ballman 6a30894391 C++2a -> C++20 in some identifiers; NFC. 2020-04-21 15:37:19 -04:00
Haojian Wu 297a9dac43 [CodeComplete] Don't replace the rest of line in #include completion.
Summary:
The previous behavior was aggressive,
  #include "abc/f^/abc.h"
                foo/  -> candidate
"f/abc.h" is replaced with "foo/", this patch will preserve the "abc.h".

Reviewers: sammccall

Subscribers: jkorous, arphaman, kadircet, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D76770
2020-03-26 11:03:04 +01:00
serge-sans-paille 3185c30c54 Prefer __vector over vector keyword for altivec
`vector' uses the keyword-and-predefine mode from gcc, while __vector is
reliably supported.

As a side effect, it also makes the code consistent in its usage of __vector.

Differential Revision: https://reviews.llvm.org/D74129
2020-02-10 20:23:26 +01:00
Benjamin Kramer adcd026838 Make llvm::StringRef to std::string conversions explicit.
This is how it should've been and brings it more in line with
std::string_view. There should be no functional change here.

This is mostly mechanical from a custom clang-tidy check, with a lot of
manual fixups. It uncovers a lot of minor inefficiencies.

This doesn't actually modify StringRef yet, I'll do that in a follow-up.
2020-01-28 23:25:25 +01:00
Scott Egerton a90ea38698 [Lexer] Allow UCN for dollar symbol '\u0024' in identifiers when using -fdollars-in-identifiers flag.
Summary:
Previously, the -fdollars-in-identifiers flag allows the '$' symbol to be used
in an identifier but the universal character name equivalent '\u0024' is not
allowed.
This patch changes this, so that \u0024 is valid in identifiers.

Reviewers: rsmith, jordan_rose

Reviewed By: rsmith

Subscribers: dexonsmith, simoncook, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D71758
2020-01-15 11:28:57 +00:00
Simon Pilgrim f2132070d9 Lexer::ReadToEndOfLine - fix Token uninitialised value warnings. NFCI.
Use Token::startToken to initialize Token.
2019-10-28 18:28:18 +00:00
Alex Lorenz ca6e60971e [clang-scan-deps] add skip excluded conditional preprocessor block preprocessing optimization
This commit adds an optimization to clang-scan-deps and clang's preprocessor that skips excluded preprocessor
blocks by bumping the lexer pointer, and not lexing the tokens until reaching appropriate #else/#endif directive.
The skip positions and lexer offsets are computed when the file is minimized, directly from the minimized tokens.

On an 18-core iMacPro with macOS Catalina Beta I got 10-15% speed-up from this optimization when running clang-scan-deps on
the compilation database for a recent LLVM and Clang (3511 files).

Differential Revision: https://reviews.llvm.org/D67127

llvm-svn: 371656
2019-09-11 20:40:31 +00:00
Fangrui Song 90e95bb289 Delete dead stores
llvm-svn: 365901
2019-07-12 14:04:34 +00:00
Richard Smith 91e150d54c Replace tok::angle_string_literal with new tok::header_name.
Use the new kind for both angled header-name tokens and for
double-quoted header-name tokens.

This is in preparation for C++20's context-sensitive header-name token
formation rules.

llvm-svn: 356530
2019-03-19 22:09:55 +00:00