Remove space after negative sign in Literal to_string

[dtolnay]

Negative proc macro literal tokens used to be printed with a space between the minus sign and the magnitude. That's because impl ToString for Literal used to convert the Literal into a TokenStream, which splits the minus sign into a separate Punct token.

Literal::isize_unsuffixed(-10).to_string()// "- 10"

This PR updates the ToString impl to directly use rustc_ast::token::Lit's ToString, which matches the way Rust negative numbers are idiomatically written without a space.

Literal::isize_unsuffixed(-10).to_string()// "-10"

[rust-highfive]

r? @cjgillot

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[cjgillot]

Can this change cause any breakage in proc-macro user code?

[dtolnay]

@cjgillot: trivially yes, for example the following user code would break.

assert_eq!(Literal::isize_unsuffixed(-10).to_string(),"- 10");

But in general token printing only guarantees that the resulting string is valid Rust that parses to the same AST (though lossy with respect to hygiene). It does not guarantee that the precise positioning of every whitespace, trailing commas, and similar details irrelevant to Rust syntax are always kept identical across all versions of the printer.

References:

• pprust: Improve pretty-printing of delimited token groups #62667
• [1.38] Regression: proc macro panicked #63894 (comment)

[Aaron1011]

r=me once #87262 lands (since the test output will be changed).

[bors]

☔ The latest upstream changes (presumably #87262) made this pull request unmergeable. Please resolve the merge conflicts.

[dtolnay]

• Rebased to resolve conflict with Support negative numbers in Literal::from_str #87262

[dtolnay]

@bors r=Aaron1011

[bors]

📌 Commit 3744dc8 has been approved by Aaron1011