Can we allow integer literals like 1 to be inferred to floating point type?

Background

In rust today, an integer like 1 cannot be inferred to floating point type. This means that valid-looking numeric expressions like 22.5 + 1 will not compile, and one must instead write 22.5 + 1.0. Can/should we change this?

History

This was discussed on Zulip in May 2020. Some of the key highlights from the discussion were:

• Floating point literals are prone to many surprises that integers are not. For example, 20_000_000 + 1, if inferred to f32 type, would have the final value 20_000_000.0. This leads some to conclude that “the surprise factor of floats is so high that they are qualitatively different than integers”.
• But there are a lot of similar surprising things:
  • 20_000_001_f32, for example, is also going to be 20_000_000.
  • Integer overflow can mean that 255 + 1 has the value 0.
• Some key questions to consider:
  • How often does adding .0 result in some insight?
  • How much would seeing the .0 help to debug a tricky problem?
• Balanced against the annoyance and surprise factor.