Float constant evaluation showing incorrect values

[tjkirch]

rust-analyzer version: (eg. output of "rust-analyzer: Show RA Version" command, accessible in VSCode via Ctrl/⌘+Shift+P)

• 0.3.1426-standalone (2023-03-06)
• 0.3.1498-standalone (2023-05-01)
• Several releases between those, when I did basic bisecting

rustc version: (eg. output of rustc -V)

• rustc 1.69.0 (84c898d65 2023-04-16)
• Also rustc 1.69.0-nightly (ef934d9b6 2023-02-08)

relevant settings: (eg. client settings, or environment variables like CARGO, RUSTC, RUSTUP_HOME or CARGO_HOME)

• None

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I normally use the rustup rust-analyzer, but I was excited to see const evaluation support in newer versions and wanted to try it out. I did cargo init --lib for a blank project and added the following consts:

const ANGLE_01: f64 = 180.0;
const ANGLE_02: f64 = 180.0 - 2.0;

The rust-analyzer info for the plain constant ANGLE_01 is correct:

const ANGLE_01: f64 = 180.0

The (MIR?) const evaluation is incorrect for ANGLE_02, which should just be 178.0:

const ANGLE_02: f64 = 1.0012832363282406e-306

If I change it to an f32, it's similarly wrong:

const ANGLE_02: f32 = 5.2897246e-37

I'd expect these to show 178.0, or close enough for a float. Am I misunderstanding the purpose of the const evaluation support, or am I doing something dumb?

[tjkirch]

@HKalbasi Thanks for looking at this! Things are better now in most cases. The following are correct now with rust-analyzer 2023-05-15:

• 90.0 - 28.0 shows 62.0
• 0.0 - 14.0 shows -14.0

However, others involving negatives seems to be wrong?

• -90.0 + 36.0 shows 35.950195 instead of -54.0
• -1.0 + 1.0 shows -3.0 instead of 0.0
• -1.0 + -1.0 shows -8.0 instead of -2.0