Gleam: Provide a better warning when rejecting camelCase

[pd-andy]

camelCase variables are forbidden by the compiler to eliminate bikeshedding over naming conventions, but the current error doesn't communicate that at all:

error: Syntax error
    ┌─ /.../thing..gleam:115:18
    │
115 │ pub fn overlappedBy(compare: fn (a, a) -> Order, a: Interval(a), b: Interval(a)) -> Bool {
    │                  ^^ I was not expecting this.

Expected one of: "("

It'd be good if the error explained why this is a syntax error, if you're coming from most other languages this will be quite confusing otherwise. I suggest:

error: Syntax error
    ┌─ /.../thing..gleam:115:18
    │
115 │ pub fn overlappedBy(compare: fn (a, a) -> Order, a: Interval(a), b: Interval(a)) -> Bool {
    │                  ^^ I was not expecting this.

Gleam only allows lowercase letters and underscores in variable and type names. Try:

    overlappedby
    overlapped_by

Maybe with a little hint explaining its to avoid arguments over naming styles.

[lpil]

Good idea! Thank you

[itsgreggreg]

Great suggestion. What do y'all think about:

error: Syntax error
    ┌─ /.../thing..gleam:115:18
    │
115 │ pub fn overlappedBy(compare: fn (a, a) -> Order, a: Interval(a), b: Interval(a)) -> Bool {
    │        ^^^^^^^^^^^^ This is not a valid name.

Hint: In Gleam names must start with a lowercase letter and contain only lowercase letters, numbers, and '_'.
Try: overlapped_by

For the Try: I'm thinking calling .snake_case() is probably good enough.

[lpil]

That looks perfect, let's do that

[samontea]

I'm working on this! I'll throw up a patch shortly.