Migrate format_args!() lints to to ast::FormatArgs

[m-ou-se]

Now that rust-lang/rust#106745 is merged, Clippy has access to the original parsed/processed format_args!() invocation. This hopefully means that Clippy no longer needs to do anything that depends on the exact expansion of format_args!() and implementation details of fmt::Arguments (which will undergo changes in the (near!) future).

Details:

As of rust-lang/rust#106745, the format_args!() builtin macro expands to a special ast::FormatArgs AST node, which contains nothing that is specific to the standard library's fmt::Arguments implementation. During AST lowering, this node is expanded into HIR that is specific to how fmt::Arguments is implemented, and will change in the (near) future.)

Clippy's format_args lints are currently done in late passes that use the HIR. They should be changed to use the information from ast::FormatArgs instead. (Ideally by making them early passes, but that might not always be possible.)

This is part of rust-lang/rust#99012

---

Lints to migrate:

• ManualAssert - MANUAL_ASSERT: Don't depend on FormatArgsExpn in ManualAssert. #10276
• Write: Migrate write.rs to rustc_ast::FormatArgs #10275
  • PRINT_WITH_NEWLINE
  • PRINTLN_EMPTY_STRING
  • PRINT_STDOUT
  • PRINT_STDERR
  • USE_DEBUG
  • PRINT_LITERAL
  • WRITE_WITH_NEWLINE
  • WRITELN_EMPTY_STRING
  • WRITE_LITERAL
• FormatArgs: Migrate format_args.rs to rustc_ast::FormatArgs #10484
  • FORMAT_IN_FORMAT_ARGS
  • TO_STRING_IN_FORMAT_ARGS
  • UNINLINED_FORMAT_ARGS
  • UNUSED_FORMAT_SPECS
• Replace remaining usage of FormatArgsExpn #10561
  • FormatImpl
    • RECURSIVE_FORMAT_IMPL
    • PRINT_IN_FORMAT_IMPL
  • ExplicitWrite - EXPLICIT_WRITE
  • UselessFormat - USELESS_FORMAT
  • Methods - EXPECT_FUN_CALL
  • PanicExpn::Format

[m-ou-se]

cc @Alexendoo @nyurik

[Alexendoo]

Nice to see it merged, I'll take a look some time in the next few days

[nyurik]

Congratulations on merging!!! It only took 2 (?) weeks - kinda fast :) I would be very happy to participate, but don't have as good of the AST/HIR understanding as @Alexendoo, but will be happy to review and participate as much as possible.

[m-ou-se]

I've added a to do list above with the list of lints to migrate.

I'll see if I can migrate some of them soon, because this issue is now blocking rust-lang/rust#106824

[Alexendoo]

I've got write.rs mostly done, which is

PRINT_WITH_NEWLINE,
PRINTLN_EMPTY_STRING,
PRINT_STDOUT,
PRINT_STDERR,
USE_DEBUG,
PRINT_LITERAL,
WRITE_WITH_NEWLINE,
WRITELN_EMPTY_STRING,
WRITE_LITERAL,

I'll open a PR for that soon-ish, just figuring out the nicest way of carrying over the AST parts in a way that's easily shared with other modules

[m-ou-se]

Nice!

[Alexendoo]

Opened ☝️

[m-ou-se]

Is there anything I can do to move this forward? I think most (all) of the remaining lints are blocked on #10275?

[Alexendoo]

I'll take a look at the FormatArgs ones next

[nyurik]

@Alexendoo are you address all of format-args users in rust-clippy? Anything I can help with?

[Alexendoo]

For the ones that don't need access to any hir Exprs, or something else missing, feel free to migrate them

I'll keep going until it's all migrated, hopefully after FormatArgs and Write they'll be fairly straight forward

[Alexendoo]

Opened: #10484