cpp_ls

Work in progress — under development. There is no release, no stability promise, and the internals move. Everything below is what runs today, not what is planned.

A C++ language server written in Rust. It reads a project the way a compiler does: macros are expanded, conditional compilation is resolved for the branches actually in force, #includes are inlined, and the resulting rendering is what gets parsed — because a C++ file does not mean what its characters say until a preprocessor has run.

What works today

cargo build --release --workspace --all-targets     no errors, no warnings
cargo test  --release --workspace                   green

• Parsing and rendering of a real project: zero syntax errors over the whole MSVC standard-library closure (187 files).

• Thirteen semantic checks, each with a DiagnosticCode (carried to the client as the LSP code), a severity and, where it applies, a tag:

  syntax-error  include-not-found  macro-redefined  unused  access-invisible
  missing-return  assignment-in-condition  unnecessary-branch  undefined-field
  argument-count  param-type-check  assign-type-check  return-type-mismatch
  

• Zero false positives on the standard library — the measurement this layer is built to pass:

  cargo run --release -p cpp_code_analysis --example checks_probe -- target/std-cook target/std-cook/assign-case.cpp
    assign-case.cpp:52  [assign-type-check]  `x` is initialised with a value that does not convert to `std::string`
    --- checks over 5 file(s) ---   1  assign-type-check
  

  Exactly one true positive, nothing else. Fixtures used by that measurement live in target/std-cook/.

• A finding is about the file being edited; the knowledge behind it is the project's. A check reports only on what this file writes, but it may read the index's facts about any other file — so std::string x = 123; is judged from the parameter list of std::string's constructors recorded in the index, not by parsing <string> again.

• The server side: diagnostics, completion, signature help, go to definition, references, semantic tokens, folding, inlay hints.

Where it is going

See docs/status.md — one document, describing the current state, the defects that are known and measured, and the plan. (It replaces nineteen older documents that described the process rather than the state of the code, and had drifted out of date.)

Trying it

cargo run --release --workspace --bin cpp_ls        # the server, speaking LSP on stdio

# the checks over a real project, one command
cargo run --release -p cpp_code_analysis --example checks_probe -- <include-dir> <root file>

# one check, with the declaration facts each finding came from
cargo run --release -p cpp_code_analysis --example one_check -- <include-dir> <root file> unused

Layout

crates/cpp_parser           lexer and grammar; a lossless tree plus a typed AST over it
crates/cpp_code_analysis    preprocessing and rendering, the index, the semantic model, the checks
crates/cpp_ls               the language server: LSP handlers and the session they run against