[PATCH] D154382: [ClangRepl] support code completion at a REPL

[Fred Fu via Phabricator via cfe-commits]

capfredf added inline comments.


================
Comment at: clang/lib/Interpreter/CodeCompletion.cpp:84
+  std::string AllCodeText =
+      MainInterp.getAllInput() + "\nvoid dummy(){\n" + Buffer.str() + "}";
+  auto Lines = std::count(AllCodeText.begin(), AllCodeText.end(), '\n') + 1;
----------------
v.g.vassilev wrote:
> I am not sure why we need to wrap this code. Can we teach the `TopLevelStmtDecl` to work with the code completion logic?
I think the problem has less to do with the TopLevelStmtDecl. Usually, a `TopLevelStmtDecl` instance is a successful result from `ParseXXXXX`,  but when `CodeCompletion` is triggered during parsing, nothing meaning comes out from `ParseXXXX`.  

We need to wrap our input because we need `Sema::CodeCompleteOrdinaryName` to work on code from the REPL in a different completion context than the same code from a regular source file.

In a regular C++ file, 

```
int foo = 42;
f_
```

Since top-level expressions are not supported, `foo` should not be an option. 

But in a REPL session,

```
clang-repl> int foo = 42;
clang-repl> f_
```

we are allowed to use `foo` to make a statement like `foo + 84;`.

Since the argument for `CompletionContext` to `CodeCompleteOrdinaryName` is controlled by the parsing process, ie. there is no way to configure it from outside, I think faking context is a straightforward solution. 

Alternatively, we can check if the compiler is in incremental mode and call `CodeCompleteOrdinaryName` with the context we want in parsing. Something like:

```
if (PP.isIncrementalProcessingEnabled() {
  Actions.CodeCompleteOrdinaryName(getCurScope(), Sema::PCC_Statement);
} else {
  Actions.CodeCompleteOrdinaryName(getCurScope(), Sema::PCC_Namespace);
}
```

I personally think both solutions are extensionally equivalent, but the alternative is a bit intrusive. 


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D154382/new/

https://reviews.llvm.org/D154382