[PATCH] D98488: [CodeCompletion] Avoid spurious signature help for init-list args

[Sam McCall via Phabricator via cfe-commits]

sammccall created this revision.
sammccall added a reviewer: kadircet.
Herald added subscribers: usaxena95, arphaman.
sammccall requested review of this revision.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.

Somewhat surprisingly, signature help is emitted as a side-effect of
computing the expected type of a function argument.
The reason is that both actions require enumerating the possible
function signatures and running partial overload resolution, and doing
this twice would be wasteful and complicated.

Change #1: document this, it's subtle :-)

However, sometimes we need to compute the expected type without having
reached the code completion cursor yet - in particular to allow
completion of designators.
eb4ab3358cd4dc834a761191b5531b38114f7b13 <https://reviews.llvm.org/rGeb4ab3358cd4dc834a761191b5531b38114f7b13> did this but introduced a
regression - it emits signature help in the wrong location as a side-effect.

Change #2: only emit signature help if the code completion cursor was reached.

Currently there is PP.isCodeCompletionReached(), but we can't use it
because it's set *after* running code completion.
It'd be nice to set this implicitly when the completion token is lexed,
but ConsumeCodeCompletionToken() makes this complicated.

Change #3: call cutOffParsing() *first* when seeing a completion token.

After this, the fact that the Sema::Produce*SignatureHelp() functions
are even more confusing, as they only sometimes do that.
I don't want to rename them in this patch as it's another large
mechanical change, but we should soon.

Change #4: prepare to rename ProduceSignatureHelp() to GuessArgumentType() etc.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D98488

Files:
  clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp
  clang/include/clang/Sema/Sema.h
  clang/lib/Lex/PPDirectives.cpp
  clang/lib/Lex/Preprocessor.cpp
  clang/lib/Parse/ParseDecl.cpp
  clang/lib/Parse/ParseDeclCXX.cpp
  clang/lib/Parse/ParseExpr.cpp
  clang/lib/Parse/ParseExprCXX.cpp
  clang/lib/Parse/ParseInit.cpp
  clang/lib/Parse/ParseObjc.cpp
  clang/lib/Parse/ParseOpenMP.cpp
  clang/lib/Parse/ParseStmt.cpp
  clang/lib/Parse/Parser.cpp
  clang/lib/Sema/SemaCodeComplete.cpp
  clang/test/CodeCompletion/desig-init.cpp

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