* bug: Add diagnostic information on font load error
I ran into a bug a while back that prevent me from using the plotters
library for months. I did finally figure out what was causing it: a file
in my font library documented in issue#231. Removing the file fixed my
issue, but the opaque problem is sure to ensnare others.
This PR adds a `LoadError(Cow<'static, str>)` variant to
`SelectionError` enum. It removes `Copy` because `Cow` isn't copyable.
And now when I run the test suite with the bad file in place, it reports
this error, which is far and away more helpful than before.
```sh
> RUST_BACKTRACE=1 cargo test --all
...
running 5 tests
test loaders::core_text::test::test_core_text_to_css_font_stretch ... ok
test loaders::core_text::test::test_core_text_to_css_font_weight ... ok
test sources::core_text::test::test_css_to_core_text_font_stretch ... ok
test sources::core_text::test::test_css_to_core_text_font_weight ... ok
test loaders::core_text::test::test_from_core_graphics_font ... FAILED
failures:
---- loaders::core_text::test::test_from_core_graphics_font stdout ----
thread 'loaders::core_text::test::test_from_core_graphics_font' panicked at src/loaders/core_text.rs:940:14:
called `Result::unwrap()` on an `Err` value: LoadError("Parse error on path \"/Users/shane/Library/Fonts/Arial\"")
stack backtrace:
0: rust_begin_unwind
at /rustc/07dca489ac2d933c78d3c5158e3f43beefeb02ce/library/std/src/panicking.rs:645:5
1: core::panicking::panic_fmt
at /rustc/07dca489ac2d933c78d3c5158e3f43beefeb02ce/library/core/src/panicking.rs:72:14
2: core::result::unwrap_failed
at /rustc/07dca489ac2d933c78d3c5158e3f43beefeb02ce/library/core/src/result.rs:1649:5
3: core::result::Result<T,E>::unwrap
at /rustc/07dca489ac2d933c78d3c5158e3f43beefeb02ce/library/core/src/result.rs:1073:23
4: font_kit::loaders::core_text::test::test_from_core_graphics_font
at ./src/loaders/core_text.rs:938:21
5: font_kit::loaders::core_text::test::test_from_core_graphics_font::{{closure}}
at ./src/loaders/core_text.rs:937:38
6: core::ops::function::FnOnce::call_once
at /rustc/07dca489ac2d933c78d3c5158e3f43beefeb02ce/library/core/src/ops/function.rs:250:5
7: core::ops::function::FnOnce::call_once
at /rustc/07dca489ac2d933c78d3c5158e3f43beefeb02ce/library/core/src/ops/function.rs:250:5
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
failures:
loaders::core_text::test::test_from_core_graphics_font
test result: FAILED. 4 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.04s
error: test failed, to rerun pass `--lib`
```
A variant that used `String` would suffice for this case. I tend to use
`Cow<'static, str>` on errors since many times they can be `&'static
str`.
* refactor: Prefer CannotAccessSource to new variant
* chore: Run cargo fmt.