Insert space after float literal ending with . in pretty printer

[aytey]

The pretty printer was collapsing unsuffixed float literals (like 0.) with adjacent dot tokens, producing ambiguous or invalid output:

• 0. ..45. (range) became 0...45.
• 0. ..=360. (inclusive range) became 0...=360.
• 0. .to_string() (method call) became 0..to_string()

The fix inserts a space after an unsuffixed float literal ending with . when it appears as the start expression of a range operator or the receiver of a method call or field access, preventing the trailing dot from merging with the following ., .., or ..= token. This is skipped when the expression is already parenthesized, since the closing ) naturally provides separation.

Example

before (rustc 1.96.0-nightly (3b1b0ef4d 2026-03-11)):

#![feature(prelude_import)]
#![no_std]
extern crate std;
#[prelude_import]
use ::std::prelude::rust_2015::*;
//@ pp-exact

fn main() {
    let _ = 0...45.;
    let _ = 0...=360.;
    let _ = 0...;
    let _ = 0..to_string();
}

after (this branch):

#![feature(prelude_import)]
#![no_std]
extern crate std;
#[prelude_import]
use ::std::prelude::rust_2015::*;
//@ pp-exact

fn main() {
    let _ = 0. ..45.;
    let _ = 0. ..=360.;
    let _ = 0. ..;
    let _ = 0. .to_string();
}

Notice 0...45. (ambiguous — looks like deprecated ... inclusive range) becomes 0. ..45. (clear: float 0. followed by range ..). Similarly 0..to_string() (parsed as range) becomes 0. .to_string() (method call on float).

[rustbot]

r? @jackh726

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• Owners of files modified in this PR: compiler
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[Kivooeo]

r? me @bors r+ rollup

[rust-bors]

📌 Commit e9740a4 has been approved by Kivooeo

It is now in the queue for this repository.