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Prefer using scope guard for `fallback::unforce()` 

This scope guard ensure that `fallback::unforce()` will be called even
if the program panics during compilation.
This commit is contained in:
Kogia-sima 2021-02-03 15:52:14 +09:00
parent 5e12280df1
commit 10ab29be85
1 changed files with 22 additions and 9 deletions
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31
sailfish-compiler/src/procmacro.rs
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@ -130,17 +130,30 @@ fn compile(
output_file: &Path,
config: Config,
) -> Result<CompilationReport, Error> {
struct FallbackScope {}
impl FallbackScope {
fn new() -> Self {
// SAFETY:
// Any token or span constructed after `proc_macro2::fallback::force()` must
// not outlive after `unforce()` because it causes span mismatch error. In
// this case, we must ensure that `compile_file` does not return any token or
// span.
proc_macro2::fallback::force();
FallbackScope {}
}
}
impl Drop for FallbackScope {
fn drop(&mut self) {
proc_macro2::fallback::unforce();
}
}
let compiler = Compiler::with_config(config);
// SAFETY:
// Any token or span constructed after `proc_macro2::fallback::force()` must not
// outlive after `unforce()` because it causes span mismatch error. In this case,
// We must ensure that `result` variable does not hold any token or span.
proc_macro2::fallback::force();
let result = compiler.compile_file(input_file, &*output_file);
proc_macro2::fallback::unforce();
result
let _scope = FallbackScope::new();
compiler.compile_file(input_file, &*output_file)
}
fn derive_template_impl(tokens: TokenStream) -> Result<TokenStream, syn::Error> {