Struct rustc_middle::mir::LocalDecl
source · pub struct LocalDecl<'tcx> {
pub mutability: Mutability,
pub local_info: Option<Box<LocalInfo<'tcx>>>,
pub internal: bool,
pub is_block_tail: Option<BlockTailInfo>,
pub ty: Ty<'tcx>,
pub user_ty: Option<Box<UserTypeProjections>>,
pub source_info: SourceInfo,
}
Expand description
A MIR local.
This can be a binding declared by the user, a temporary inserted by the compiler, a function argument, or the return place.
Fields
mutability: Mutability
Whether this is a mutable binding (i.e., let x
or let mut x
).
Temporaries and the return place are always mutable.
local_info: Option<Box<LocalInfo<'tcx>>>
internal: bool
true
if this is an internal local.
These locals are not based on types in the source code and are only used for a few desugarings at the moment.
The generator transformation will sanity check the locals which are live across a suspension point against the type components of the generator which type checking knows are live across a suspension point. We need to flag drop flags to avoid triggering this check as they are introduced outside of type inference.
This should be sound because the drop flags are fully algebraic, and therefore don’t affect the auto-trait or outlives properties of the generator.
is_block_tail: Option<BlockTailInfo>
If this local is a temporary and is_block_tail
is Some
,
then it is a temporary created for evaluation of some
subexpression of some block’s tail expression (with no
intervening statement context).
ty: Ty<'tcx>
The type of this local.
user_ty: Option<Box<UserTypeProjections>>
If the user manually ascribed a type to this variable,
e.g., via let x: T
, then we carry that type here. The MIR
borrow checker needs this information since it can affect
region inference.
source_info: SourceInfo
The syntactic (i.e., not visibility) source scope the local is defined in. If the local was defined in a let-statement, this is within the let-statement, rather than outside of it.
This is needed because the visibility source scope of locals within a let-statement is weird.
The reason is that we want the local to be within the let-statement for lint purposes, but we want the local to be after the let-statement for names-in-scope purposes.
That’s it, if we have a let-statement like the one in this function:
fn foo(x: &str) {
#[allow(unused_mut)]
let mut x: u32 = { // <- one unused mut
let mut y: u32 = x.parse().unwrap();
y + 2
};
drop(x);
}
Then, from a lint point of view, the declaration of x: u32
(and y: u32
) are within the #[allow(unused_mut)]
scope - the
lint scopes are the same as the AST/HIR nesting.
However, from a name lookup point of view, the scopes look more like
as if the let-statements were match
expressions:
fn foo(x: &str) {
match {
match x.parse::<u32>().unwrap() {
y => y + 2
}
} {
x => drop(x)
};
}
We care about the name-lookup scopes for debuginfo - if the
debuginfo instruction pointer is at the call to x.parse()
, we
want x
to refer to x: &str
, but if it is at the call to
drop(x)
, we want it to refer to x: u32
.
To allow both uses to work, we need to have more than a single scope
for a local. We have the source_info.scope
represent the “syntactic”
lint scope (with a variable being under its let block) while the
var_debug_info.source_info.scope
represents the “local variable”
scope (where the “rest” of a block is under all prior let-statements).
The end result looks like this:
ROOT SCOPE
│{ argument x: &str }
│
│ │{ #[allow(unused_mut)] } // This is actually split into 2 scopes
│ │ // in practice because I'm lazy.
│ │
│ │← x.source_info.scope
│ │← `x.parse().unwrap()`
│ │
│ │ │← y.source_info.scope
│ │
│ │ │{ let y: u32 }
│ │ │
│ │ │← y.var_debug_info.source_info.scope
│ │ │← `y + 2`
│
│ │{ let x: u32 }
│ │← x.var_debug_info.source_info.scope
│ │← `drop(x)` // This accesses `x: u32`.
Implementations
sourceimpl<'tcx> LocalDecl<'tcx>
impl<'tcx> LocalDecl<'tcx>
sourcepub fn can_be_made_mutable(&self) -> bool
pub fn can_be_made_mutable(&self) -> bool
Returns true
only if local is a binding that can itself be
made mutable via the addition of the mut
keyword, namely
something like the occurrences of x
in:
fn foo(x: Type) { ... }
,let x = ...
,- or
match ... { C(x) => ... }
sourcepub fn is_nonref_binding(&self) -> bool
pub fn is_nonref_binding(&self) -> bool
Returns true
if local is definitely not a ref ident
or
ref mut ident
binding. (Such bindings cannot be made into
mutable bindings, but the inverse does not necessarily hold).
sourcepub fn is_user_variable(&self) -> bool
pub fn is_user_variable(&self) -> bool
Returns true
if this variable is a named variable or function
parameter declared by the user.
sourcepub fn is_ref_for_guard(&self) -> bool
pub fn is_ref_for_guard(&self) -> bool
Returns true
if this is a reference to a variable bound in a match
expression that is used to access said variable for the guard of the
match arm.
sourcepub fn is_ref_to_static(&self) -> bool
pub fn is_ref_to_static(&self) -> bool
Returns Some
if this is a reference to a static item that is used to
access that static.
sourcepub fn is_ref_to_thread_local(&self) -> bool
pub fn is_ref_to_thread_local(&self) -> bool
Returns Some
if this is a reference to a thread-local static item that is used to
access that static.
sourcepub fn is_deref_temp(&self) -> bool
pub fn is_deref_temp(&self) -> bool
Returns true
if this is a DerefTemp
sourcepub fn from_compiler_desugaring(&self) -> bool
pub fn from_compiler_desugaring(&self) -> bool
Returns true
is the local is from a compiler desugaring, e.g.,
__next
from a for
loop.
sourcepub fn new(ty: Ty<'tcx>, span: Span) -> Self
pub fn new(ty: Ty<'tcx>, span: Span) -> Self
Creates a new LocalDecl
for a temporary: mutable, non-internal.
sourcepub fn with_source_info(ty: Ty<'tcx>, source_info: SourceInfo) -> Self
pub fn with_source_info(ty: Ty<'tcx>, source_info: SourceInfo) -> Self
Like LocalDecl::new
, but takes a SourceInfo
instead of a Span
.
sourcepub fn block_tail(self, info: BlockTailInfo) -> Self
pub fn block_tail(self, info: BlockTailInfo) -> Self
Converts self
into same LocalDecl
except tagged as internal temporary.
Trait Implementations
sourceimpl<'tcx, '__ctx> HashStable<StableHashingContext<'__ctx>> for LocalDecl<'tcx>
impl<'tcx, '__ctx> HashStable<StableHashingContext<'__ctx>> for LocalDecl<'tcx>
fn hash_stable(
&self,
__hcx: &mut StableHashingContext<'__ctx>,
__hasher: &mut StableHasher
)
sourceimpl<'tcx> TypeFoldable<'tcx> for LocalDecl<'tcx>
impl<'tcx> TypeFoldable<'tcx> for LocalDecl<'tcx>
sourcefn try_fold_with<__F: FallibleTypeFolder<'tcx>>(
self,
__folder: &mut __F
) -> Result<Self, __F::Error>
fn try_fold_with<__F: FallibleTypeFolder<'tcx>>(
self,
__folder: &mut __F
) -> Result<Self, __F::Error>
sourcefn fold_with<F: TypeFolder<'tcx>>(self, folder: &mut F) -> Self
fn fold_with<F: TypeFolder<'tcx>>(self, folder: &mut F) -> Self
try_fold_with
for use with infallible
folders. Do not override this method, to ensure coherence with
try_fold_with
. Read moresourceimpl<'tcx> TypeVisitable<'tcx> for LocalDecl<'tcx>
impl<'tcx> TypeVisitable<'tcx> for LocalDecl<'tcx>
sourcefn visit_with<__V: TypeVisitor<'tcx>>(
&self,
__visitor: &mut __V
) -> ControlFlow<__V::BreakTy>
fn visit_with<__V: TypeVisitor<'tcx>>(
&self,
__visitor: &mut __V
) -> ControlFlow<__V::BreakTy>
sourcefn has_vars_bound_at_or_above(&self, binder: DebruijnIndex) -> bool
fn has_vars_bound_at_or_above(&self, binder: DebruijnIndex) -> bool
true
if self
has any late-bound regions that are either
bound by binder
or bound by some binder outside of binder
.
If binder
is ty::INNERMOST
, this indicates whether
there are any late-bound regions that appear free. Read moresourcefn has_vars_bound_above(&self, binder: DebruijnIndex) -> bool
fn has_vars_bound_above(&self, binder: DebruijnIndex) -> bool
true
if this self
has any regions that escape binder
(and
hence are not bound by it). Read morefn has_escaping_bound_vars(&self) -> bool
fn has_type_flags(&self, flags: TypeFlags) -> bool
fn has_projections(&self) -> bool
fn has_opaque_types(&self) -> bool
fn references_error(&self) -> bool
fn error_reported(&self) -> Option<ErrorGuaranteed>
fn has_param_types_or_consts(&self) -> bool
fn has_infer_regions(&self) -> bool
fn has_infer_types(&self) -> bool
fn has_infer_types_or_consts(&self) -> bool
fn needs_infer(&self) -> bool
fn has_placeholders(&self) -> bool
fn needs_subst(&self) -> bool
sourcefn has_free_regions(&self) -> bool
fn has_free_regions(&self) -> bool
fn has_erased_regions(&self) -> bool
sourcefn has_erasable_regions(&self) -> bool
fn has_erasable_regions(&self) -> bool
sourcefn is_global(&self) -> bool
fn is_global(&self) -> bool
sourcefn has_late_bound_regions(&self) -> bool
fn has_late_bound_regions(&self) -> bool
sourcefn still_further_specializable(&self) -> bool
fn still_further_specializable(&self) -> bool
impl
specialization. Read moreAuto Trait Implementations
impl<'tcx> !RefUnwindSafe for LocalDecl<'tcx>
impl<'tcx> !Send for LocalDecl<'tcx>
impl<'tcx> !Sync for LocalDecl<'tcx>
impl<'tcx> Unpin for LocalDecl<'tcx>
impl<'tcx> !UnwindSafe for LocalDecl<'tcx>
Blanket Implementations
sourceimpl<T> BorrowMut<T> for Twhere
T: ?Sized,
impl<T> BorrowMut<T> for Twhere
T: ?Sized,
const: unstable · sourcefn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
sourceimpl<Ctxt, T> DepNodeParams<Ctxt> for Twhere
Ctxt: DepContext,
T: for<'a> HashStable<StableHashingContext<'a>> + Debug,
impl<Ctxt, T> DepNodeParams<Ctxt> for Twhere
Ctxt: DepContext,
T: for<'a> HashStable<StableHashingContext<'a>> + Debug,
default fn fingerprint_style() -> FingerprintStyle
sourcedefault fn to_fingerprint(&self, tcx: Ctxt) -> Fingerprint
default fn to_fingerprint(&self, tcx: Ctxt) -> Fingerprint
default fn to_debug_str(&self, Ctxt) -> String
sourcedefault fn recover(Ctxt, &DepNode<<Ctxt as DepContext>::DepKind>) -> Option<T>
default fn recover(Ctxt, &DepNode<<Ctxt as DepContext>::DepKind>) -> Option<T>
DepNode
,
something which is needed when forcing DepNode
s during red-green
evaluation. The query system will only call this method if
fingerprint_style()
is not FingerprintStyle::Opaque
.
It is always valid to return None
here, in which case incremental
compilation will treat the query as having changed instead of forcing it. Read moresourceimpl<T, R> InternIteratorElement<T, R> for T
impl<T, R> InternIteratorElement<T, R> for T
type Output = R
fn intern_with<I, F>(iter: I, f: F) -> <T as InternIteratorElement<T, R>>::Outputwhere
I: Iterator<Item = T>,
F: FnOnce(&[T]) -> R,
sourceimpl<T> MaybeResult<T> for T
impl<T> MaybeResult<T> for T
sourceimpl<CTX, T> Value<CTX> for Twhere
CTX: DepContext,
impl<CTX, T> Value<CTX> for Twhere
CTX: DepContext,
default fn from_cycle_error(tcx: CTX) -> T
impl<'a, T> Captures<'a> for Twhere
T: ?Sized,
Layout
Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain repr(...)
attributes. Please see the Rust Reference’s “Type Layout” chapter for details on type layout guarantees.
Size: 56 bytes