New lint: too_many_lines_in_file

[tupe12334]

Closes #16674

Summary

Adds a new restriction lint too_many_lines_in_file that warns when a source file exceeds a configurable number of lines of code. Blank lines and comment-only lines are not counted, matching the behavior of the existing too_many_lines function-level lint.

Configuration

too-many-lines-in-file-threshold in clippy.toml (default: 1000)

Example diagnostic

warning: this file has too many lines (1200/1000)
  --> src/my_module.rs:1:1
   |
 1 | // src/my_module.rs
   | ^

Implementation notes

• Uses an EarlyLintPass with check_crate, iterating all source files in the session source map
• Filters to local crate files only (file.cnum == LOCAL_CRATE) to avoid checking dependencies
• Line counting logic mirrors too_many_lines: skips blank lines and comment-only lines (including /* */ block comments)
• Span points to file.start_pos (line 1, col 1 of the file)

Disclosure

The code in this PR was generated with the assistance of Claude Code, Anthropic's AI coding assistant.

changelog: new lint: [too_many_lines_in_file]

[rustbot]

r? @llogiq

rustbot has assigned @llogiq.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

Why was this reviewer chosen?

The reviewer was selected based on:

• Owners of files modified in this PR: 7 candidates
• 7 candidates expanded to 7 candidates
• Random selection from Jarcho, dswij, llogiq, samueltardieu

[github-actions]

Lintcheck changes for 2c4c95a

Lint	Added	Removed	Changed
clippy::too_many_lines_in_file	154	0	0

This comment will be updated if you push new changes

[rustbot]

⚠️ Warning ⚠️

• There are issue links (such as #123) in the commit messages of the following commits.
  Please move them to the PR description, to avoid spamming the issues with references to the commit, and so this bot can automatically canonicalize them to avoid issues with subtree.
  • 2c4c95a