Lived Experiences: Strange match ergonomics

[rpjohnst]

@H2CO3

That is the exact problem, thanks for pointing it out and phrasing it so well. The binding modes changing semantics (value -> reference) without a change in syntax (nothing -> ref ) are doing exactly what is the anti-thesis of good language and API design: “things that look similar should be similar, and things that look different should be different”. With the introduction of default binding modes, two bindings that look identical can radically differ in their behavior (owning vs borrowing), while two bindings that differ in the existence of the ref qualifier can behave identically (both borrowing).

This has been "broken" since before 1.0. let x = y; already "radically differs" in owning vs borrowing based on whether y is a reference. All match ergonomics does is allow this sort of thing to pass through patterns, by eliding part of the structure of types (the part built out of references).

Your jab about "local reasoning" in compilers is also incredibly disingenuous. None of the local reasoning a compiler does is at all thwarted by match ergonomics.