[colbymchenry]

Problem

Found while triaging the A/B for #2707. A Rust name written through a path is an item of what the path names: a module (ast::Pattern, io::Error), a type (Source::Record { … }) or a crate (mio::Interest, std::ffi::OsStr).

isRustNameInScope accepted any candidate in the file the path is written in, whatever the path said. It refused a std path's candidate only when the candidate was in another file. So a path linked to a same-named item that merely shared its file:

• clap's std::ffi::OsStr linked to its own struct OsStr. In error/mod.rs, io::Error, fmt::Error, error::Error and fmt::Result linked to its own Error and Result.
• tokio's mio::Interest linked to its own Interest, std::time::Instant to its own Instant, and std::fs::ReadDir to its own ReadDir.
• serde's tests' Token::Struct { … }, Token::Seq, Token::Map and the like, all variants of serde_test's Token, linked to the test files' own Struct types and variants: 317 links. serde_derive's syn::Path { … } linked to a Default::Path variant.
• gleam's ast::Pattern linked to the enum Pattern beside it. BinaryBuilderPosition::RecordAttribute { … } linked to ErlangSourceBuilderPosition::RecordAttribute, another enum's variant of that name, and the same happened to 90 more variant literals.

Fix

All three changes are in the path branch of isRustNameInScope.

1. A path from std, core, alloc or a crate the manifests depend on names nothing of the project's, in any file. The exceptions are a project that is that crate and a file whose own use binds the root.
2. The same-file shortcut is gone. A candidate is what the path names when one of these holds:
   • its file is the path's module;
   • its qualified name holds the segment, as a type's variant or method does;
   • it sits in an inline mod of that name in the file (isInRustInlineModule). An inline module adds nothing to its items' qualified names, and rustfmt closes the block at the indentation it opens at.
3. Through a module a use binds, a candidate must be in a crate that use's path can reach. This is rustUseCanReach, as a bare name already gets. Without it, removing the same-file shortcut sent tokio's io::Handle (under use crate::runtime::io) to tokio-test's io.rs Handle, a dev-dependency's. It now reaches runtime/io/driver.rs's.

Verification

• __tests__/rust-path-same-file.test.ts, 6 tests, on both engines. It covers:
  • ast::Pattern beside an own enum Pattern, which still links from a bare Pattern;
  • io::Error, fmt::Result and error::Error in error/mod.rs;
  • mio::Interest and std::ffi::OsStr;
  • Source::Record { … } beside another enum's Record;
  • inner::Cell from an inline mod inner;
  • in a workspace, io::Handle under use crate::runtime::io beside a dev-dependency's io.rs Handle.
• Red on main. 5 of the 6 fail against main's name-matcher.ts; the sixth is the inline-module guard. With only the crate-reach rule switched off, the workspace test fails.
• tsc is clean. The Rust suites pass (17 files, 334 tests): this one, fix(rust): an impl's associated type or const no longer takes a bare name or a module path #2707's, parity, fix(rust): a call through a Pin, Rc or Box self reaches the method Rust picks, inherent first #2701's, the other Rust resolution suites and resolution.test.ts.
• Full suite on main 63476df plus this change, with CODEGRAPH_KERNEL_EXPECT=1 --maxWorkers=4 --minWorkers=1 and the kernel built: 7,796 tests, 7,714 passed, 0 failed, 82 skipped.
• Rebased onto 5a7a434. The new commits are C, C++, TS and Express, plus fix(rust): a call on what as_mut() hands back reaches the receiver's declared type #2710, whose Rust as_mut() method-call receivers are a separate path from this one. The kernel was rebuilt for fix(resolution): honour TypeScript type modifiers on imports and re-exports #1955's tsjs change. tsc, the Rust suites with fix(rust): a call on what as_mut() hands back reaches the receiver's declared type #2710's, and the incoming C, C++, TS and Express tests (tsjs parity, frameworks.test.ts) all pass; this suite also passes on wasm.

A/B on real repos

Arms: main b5553e2 (#2707), and this change on it. The later main commits change C, C++, TS and Express only. Both use the same kernel, since this change is in the resolver only. Every repo was indexed fresh with codegraph init -y, dumped with scripts/dump-graph.mjs, and edges were paired by kind, source, line and column. Every changed site was triaged: the written path was read from the source, and the old and new targets were checked against it. No edge was added.

Repo	Wrong links gone	Moved to the path's own target	Same target, new metadata
axum	16	2	0
tokio	27	10	1
clap	33	0	0
serde	328	11	15
ripgrep	20	4	4
gleam	15	124	53
dioxus	31	41	4

• Gone (470). Every removed link went through std (std::, io::, fmt::, fs::, error::, task::), a dependency (mio::, syn::, tungstenite::, walkdir::, lsp_server::, pubgrub::, backtrace::, anyhow::, proc_macro2::, axum-extra's cookie::) or an alias of one (ts::Message, TMessage::Close), or through serde_test's Token::. In each case it reached a same-named project item that the path doesn't lead to.
  • The serde tests account for 317 of these, and serde_derive's syn:: paths for 15.
  • tokio's sys::Blocking is crate::blocking::JoinHandle re-exported under that name from io/mod.rs's inline mod sys, not io/blocking.rs's own struct Blocking.
• Moved (192). Each now reaches the item the path names:
  • gleam's 22 ast::Pattern reach ast.rs's enum;
  • gleam's 91 enum-variant literals, like BinaryBuilderPosition::RecordAttribute { … } or BitArrayOption::Utf16, reach the variant of the enum they name;
  • dioxus's and serde's variant literals do the same;
  • tokio's driver::Handle, io::Handle, io::Driver, list::Tx and super::task::trace::Trace reach the module the path walks.
• Same target, new metadata (77). These now link at 0.9 as a unique match, because a same-file namesake no longer competes.
• Controls. gin, serilog, flask and express are byte-identical.
• Cost. Three interleaved rounds per arm, median CPU seconds: tokio 30.3 → 29.8, gleam 26.7 → 27.7, serde 6.1 → 6.5. That is within run-to-run noise.

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