[clangd] Use identifiers in file as completion candidates when build is not ready.

Summary:
o Lex the code to get the identifiers and put them into a "symbol" index.
o Adds a new completion mode without compilation/sema into code completion workflow.
o Make IncludeInserter work even when no compile command is present, by avoiding
inserting non-verbatim headers.

Reviewers: sammccall

Reviewed By: sammccall

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, kadircet, jdoerfert, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D60126

llvm-svn: 358159

1 files changed, 5 insertions, 1 deletions

diff --git a/clang-tools-extra/clangd/CodeComplete.h b/clang-tools-extra/clangd/CodeComplete.h
index e1110dccc0d..9d43107a01e 100644
--- a/clang-tools-extra/clangd/CodeComplete.h
+++ b/clang-tools-extra/clangd/CodeComplete.h
@@ -225,7 +225,11 @@ struct SpeculativeFuzzyFind {
   std::future<SymbolSlab> Result;
 };
 
-/// Get code completions at a specified \p Pos in \p FileName.
+/// Gets code completions at a specified \p Pos in \p FileName.
+///
+/// If \p Preamble is nullptr, this runs code completion without compiling the
+/// code.
+///
 /// If \p SpecFuzzyFind is set, a speculative and asynchronous fuzzy find index
 /// request (based on cached request) will be run before parsing sema. In case
 /// the speculative result is used by code completion (e.g. speculation failed),