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86 lines
3.8 KiB
Rust
86 lines
3.8 KiB
Rust
#![deny(rustc::untranslatable_diagnostic)]
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#![deny(rustc::diagnostic_outside_of_impl)]
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use rustc_middle::mir::visit::{
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MutatingUseContext, NonMutatingUseContext, NonUseContext, PlaceContext,
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};
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#[derive(Eq, PartialEq, Clone)]
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pub enum DefUse {
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Def,
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Use,
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Drop,
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}
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pub fn categorize(context: PlaceContext) -> Option<DefUse> {
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match context {
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///////////////////////////////////////////////////////////////////////////
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// DEFS
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PlaceContext::MutatingUse(MutatingUseContext::Store) |
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// We let Call define the result in both the success and
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// unwind cases. This is not really correct, however it
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// does not seem to be observable due to the way that we
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// generate MIR. To do things properly, we would apply
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// the def in call only to the input from the success
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// path and not the unwind path. -nmatsakis
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PlaceContext::MutatingUse(MutatingUseContext::Call) |
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PlaceContext::MutatingUse(MutatingUseContext::AsmOutput) |
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PlaceContext::MutatingUse(MutatingUseContext::Yield) |
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// Storage live and storage dead aren't proper defines, but we can ignore
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// values that come before them.
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PlaceContext::NonUse(NonUseContext::StorageLive) |
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PlaceContext::NonUse(NonUseContext::StorageDead) => Some(DefUse::Def),
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///////////////////////////////////////////////////////////////////////////
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// REGULAR USES
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//
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// These are uses that occur *outside* of a drop. For the
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// purposes of NLL, these are special in that **all** the
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// lifetimes appearing in the variable must be live for each regular use.
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PlaceContext::NonMutatingUse(NonMutatingUseContext::Projection) |
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PlaceContext::MutatingUse(MutatingUseContext::Projection) |
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// Borrows only consider their local used at the point of the borrow.
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// This won't affect the results since we use this analysis for coroutines
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// and we only care about the result at suspension points. Borrows cannot
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// cross suspension points so this behavior is unproblematic.
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PlaceContext::MutatingUse(MutatingUseContext::Borrow) |
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PlaceContext::NonMutatingUse(NonMutatingUseContext::SharedBorrow) |
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PlaceContext::NonMutatingUse(NonMutatingUseContext::ShallowBorrow) |
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// `PlaceMention` and `AscribeUserType` both evaluate the place, which must not
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// contain dangling references.
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PlaceContext::NonMutatingUse(NonMutatingUseContext::PlaceMention) |
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PlaceContext::NonUse(NonUseContext::AscribeUserTy(_)) |
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PlaceContext::MutatingUse(MutatingUseContext::AddressOf) |
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PlaceContext::NonMutatingUse(NonMutatingUseContext::AddressOf) |
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PlaceContext::NonMutatingUse(NonMutatingUseContext::Inspect) |
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PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy) |
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PlaceContext::NonMutatingUse(NonMutatingUseContext::Move) |
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PlaceContext::MutatingUse(MutatingUseContext::Retag) =>
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Some(DefUse::Use),
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///////////////////////////////////////////////////////////////////////////
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// DROP USES
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//
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// These are uses that occur in a DROP (a MIR drop, not a
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// call to `std::mem::drop()`). For the purposes of NLL,
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// uses in drop are special because `#[may_dangle]`
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// attributes can affect whether lifetimes must be live.
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PlaceContext::MutatingUse(MutatingUseContext::Drop) =>
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Some(DefUse::Drop),
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// Debug info is neither def nor use.
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PlaceContext::NonUse(NonUseContext::VarDebugInfo) => None,
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PlaceContext::MutatingUse(MutatingUseContext::Deinit | MutatingUseContext::SetDiscriminant) => {
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bug!("These statements are not allowed in this MIR phase")
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}
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}
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}
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