This came up here but I am pretty sure I ran into this before: Rust parses -5.5f32.method() as -(5.5f32.method()). I don't know if that is the parsing result that anyone expects, I certainly would never expect it -5.5f32 is a float literals, and that is what I want to apply the method to, I never even considered that the compiler might interpret this as a unary minus applied to the method result.

Assuming that we cannot change the parser, I think we should spend some effort defending against the possible confusion here. For instance:

• lint against -5.5f32.method() (suggesting to write -(5.5f32.method()) if that's really what one meant)
• have rustfmt add the parentheses that make precedence explicit