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Rollup merge of #79809 - Eric-Arellano:split-once, r=matklad

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Dogfood `str_split_once()`

Part of https://github.com/rust-lang/rust/issues/74773.

Beyond increased clarity, this fixes some instances of a common confusion with how `splitn(2)` behaves: the first element will always be `Some()`, regardless of the delimiter, and even if the value is empty.

Given this code:

```rust
fn main() {
    let val = "...";
    let mut iter = val.splitn(2, '=');
    println!("Input: {:?}, first: {:?}, second: {:?}", val, iter.next(), iter.next());
}
```

We get:

```
Input: "no_delimiter", first: Some("no_delimiter"), second: None
Input: "k=v", first: Some("k"), second: Some("v")
Input: "=", first: Some(""), second: Some("")
```

Using `str_split_once()` makes more clear what happens when the delimiter is not found.
This commit is contained in:
Tyler Mandry 2020-12-10 21:33:08 -08:00 • committed by GitHub
commit 17ec4b8258
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22 changed files with 197 additions and 191 deletions
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1
compiler/rustc_mir/src/lib.rs
View file

@ -28,6 +28,7 @@ Rust MIR: a lowered representation of Rust.
#![feature(or_patterns)]
#![feature(once_cell)]
#![feature(control_flow_enum)]
#![feature(str_split_once)]
#![recursion_limit = "256"]
#[macro_use]

62
compiler/rustc_mir/src/transform/coverage/debug.rs
View file

@ -148,40 +148,46 @@ impl DebugOptions {
if let Ok(env_debug_options) = std::env::var(RUSTC_COVERAGE_DEBUG_OPTIONS) {
for setting_str in env_debug_options.replace(" ", "").replace("-", "_").split(',') {
let mut setting = setting_str.splitn(2, '=');
match setting.next() {
Some(option) if option == "allow_unused_expressions" => {
allow_unused_expressions = bool_option_val(option, setting.next());
let (option, value) = match setting_str.split_once('=') {
None => (setting_str, None),
Some((k, v)) => (k, Some(v)),
};
match option {
"allow_unused_expressions" => {
allow_unused_expressions = bool_option_val(option, value);
debug!(
"{} env option `allow_unused_expressions` is set to {}",
RUSTC_COVERAGE_DEBUG_OPTIONS, allow_unused_expressions
);
}
Some(option) if option == "counter_format" => {
if let Some(strval) = setting.next() {
counter_format = counter_format_option_val(strval);
debug!(
"{} env option `counter_format` is set to {:?}",
RUSTC_COVERAGE_DEBUG_OPTIONS, counter_format
);
} else {
bug!(
"`{}` option in environment variable {} requires one or more \
plus-separated choices (a non-empty subset of \
`id+block+operation`)",
option,
RUSTC_COVERAGE_DEBUG_OPTIONS
);
}
"counter_format" => {
match value {
None => {
bug!(
"`{}` option in environment variable {} requires one or more \
plus-separated choices (a non-empty subset of \
`id+block+operation`)",
option,
RUSTC_COVERAGE_DEBUG_OPTIONS
);
}
Some(val) => {
counter_format = counter_format_option_val(val);
debug!(
"{} env option `counter_format` is set to {:?}",
RUSTC_COVERAGE_DEBUG_OPTIONS, counter_format
);
}
};
}
Some("") => {}
Some(invalid) => bug!(
"Unsupported setting `{}` in environment variable {}",
invalid,
RUSTC_COVERAGE_DEBUG_OPTIONS
),
None => {}
}
_ => {
bug!(
"Unsupported setting `{}` in environment variable {}",
option,
RUSTC_COVERAGE_DEBUG_OPTIONS
)
}
};
}
}