bjoernager/rust
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Improve with_source_map.

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Rename `with_source_map` as `set_source_map`. Because `with` functions
(e.g. `with_session_globals`, `scoped_tls::ScopedKey::with`) are for
*getting* a value for the duration of a closure, and `set` functions
(e.g. `set_session_globals_then` `scoped_tls::ScopedKey::with`) are for
*setting* a value for the duration of a closure.

Also fix up the comment, which is wrong:
- The bit about `TyCtxt` is wrong.
- `span_debug1` doesn't exist any more.
- There's only one level of fallback, not two.

(This is effectively a follow-up to the changes in #93936.)

Also add a comment explaining that `SessionGlobals::source_map` should
only be used when absolutely necessary.
This commit is contained in:
Nicholas Nethercote 2023-03-31 14:54:25 +11:00
parent f049d5df10
commit 4e63ab6fc1
2 changed files with 14 additions and 11 deletions
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23
compiler/rustc_span/src/lib.rs
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@ -87,6 +87,14 @@ pub struct SessionGlobals {
symbol_interner: symbol::Interner,
span_interner: Lock<span_encoding::SpanInterner>,
hygiene_data: Lock<hygiene::HygieneData>,
/// A reference to the source map in the `Session`. It's an `Option`
/// because it can't be initialized until `Session` is created, which
/// happens after `SessionGlobals`. `set_source_map` does the
/// initialization.
///
/// This field should only be used in places where the `Session` is truly
/// not available, such as `<Span as Debug>::fmt`.
source_map: Lock<Option<Lrc<SourceMap>>>,
}
@ -1013,16 +1021,9 @@ impl<D: Decoder> Decodable<D> for Span {
}
}
/// Calls the provided closure, using the provided `SourceMap` to format
/// any spans that are debug-printed during the closure's execution.
///
/// Normally, the global `TyCtxt` is used to retrieve the `SourceMap`
/// (see `rustc_interface::callbacks::span_debug1`). However, some parts
/// of the compiler (e.g. `rustc_parse`) may debug-print `Span`s before
/// a `TyCtxt` is available. In this case, we fall back to
/// the `SourceMap` provided to this function. If that is not available,
/// we fall back to printing the raw `Span` field values.
pub fn with_source_map<T, F: FnOnce() -> T>(source_map: Lrc<SourceMap>, f: F) -> T {
/// Insert `source_map` into the session globals for the duration of the
/// closure's execution.
pub fn set_source_map<T, F: FnOnce() -> T>(source_map: Lrc<SourceMap>, f: F) -> T {
with_session_globals(|session_globals| {
*session_globals.source_map.borrow_mut() = Some(source_map);
});
@ -1041,6 +1042,8 @@ pub fn with_source_map<T, F: FnOnce() -> T>(source_map: Lrc<SourceMap>, f: F) ->
impl fmt::Debug for Span {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
// Use the global `SourceMap` to print the span. If that's not
// available, fall back to printing the raw values.
with_session_globals(|session_globals| {
if let Some(source_map) = &*session_globals.source_map.borrow() {
write!(f, "{} ({:?})", source_map.span_to_diagnostic_string(*self), self.ctxt())