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Module cast

rustc_hir_typeck

Module cast 

Source
Expand description

Code for type-checking cast expressions.

A cast e as U is valid if one of the following holds:

  • e has type T and T coerces to U; coercion-cast
  • e has type *T, U is *U_0, and either U_0: Sized or pointer_kind(T) = pointer_kind(U_0); ptr-ptr-cast
  • e has type *T and U is a numeric type, while T: Sized; ptr-addr-cast
  • e is an integer and U is *U_0, while U_0: Sized; addr-ptr-cast
  • e has type T and T and U are any numeric types; numeric-cast
  • e is a C-like enum and U is an integer type; enum-cast
  • e has type bool or char and U is an integer; prim-int-cast
  • e has type u8 and U is char; u8-char-cast
  • e has type &[T; n] and U is *const T; array-ptr-cast
  • e is a function pointer type and U has type *T, while T: Sized; fptr-ptr-cast
  • e is a function pointer type and U is an integer; fptr-addr-cast

where &.T and *T are references of either mutability, and where pointer_kind(T) is the kind of the unsize info in T - the vtable for a trait definition (e.g., fmt::Display or Iterator, not Iterator<Item=u8>) or a length (or () if T: Sized).

Note that lengths are not adjusted when casting raw slices - T: *const [u16] as *const [u8] creates a slice that only includes half of the original memory.

Casting is not transitive, that is, even if e as U1 as U2 is a valid expression, e as U2 is not necessarily so (in fact it will only be valid if U1 coerces to U2).

Re-exports§

use rustc_data_structures::fx::FxHashSet; 🔒
use rustc_errors::Applicability; 🔒
use rustc_errors::Diag; 🔒
use rustc_errors::ErrorGuaranteed; 🔒
use rustc_hir::def_id::DefId; 🔒
use rustc_hir::def_id::LocalDefId; 🔒
use rustc_hir as hir; 🔒
use rustc_hir::ExprKind; 🔒
use rustc_infer::infer::DefineOpaqueTypes; 🔒
use rustc_infer::traits::ObligationCauseCode; 🔒
use rustc_lint_defs::builtin::TRIVIAL_CASTS; 🔒
use rustc_lint_defs::builtin::TRIVIAL_NUMERIC_CASTS; 🔒
use rustc_macros::TypeFoldable; 🔒
use rustc_macros::TypeVisitable; 🔒
use rustc_middle::mir::Mutability; 🔒
use rustc_middle::ty::adjustment::AllowTwoPhase; 🔒
use rustc_middle::ty::cast::CastTy; 🔒
use rustc_middle::ty::error::TypeError; 🔒
use rustc_middle::ty; 🔒
use rustc_middle::ty::Ty; 🔒
use rustc_middle::ty::TyCtxt; 🔒
use rustc_middle::ty::TypeAndMut; 🔒
use rustc_middle::ty::TypeVisitableExt; 🔒
use rustc_middle::ty::Unnormalized; 🔒
use rustc_middle::ty::VariantDef; 🔒
use rustc_middle::ty::elaborate; 🔒
use rustc_span::DUMMY_SP; 🔒
use rustc_span::Span; 🔒
use rustc_span::bug; 🔒
use rustc_span::span_bug; 🔒
use rustc_span::sym; 🔒
use rustc_trait_selection::infer::InferCtxtExt; 🔒
use rustc_trait_selection::traits; 🔒
use rustc_trait_selection::traits::ObligationCtxt; 🔒
use rustc_trait_selection::traits::TraitEngine; 🔒
use tracing::debug; 🔒
use tracing::instrument; 🔒
use tracing::instrument; 🔒
use super::FnCtxt; 🔒
use crate::diagnostics; 🔒
use crate::type_error_struct; 🔒
use rustc_errors::codes::*; 🔒

Structs§

CastCheck 🔒
Reifies a cast check to be checked once we have full type information for a function context.

Enums§

CastError 🔒
CastKind
Cast Kind. See RFC 401 (or rustc_hir_typeck/src/cast.rs).
PointerKind 🔒
The kind of pointer and associated metadata (thin, length or vtable) - we only allow casts between wide pointers if their metadata have the same kind.

Functions§

check_cast
If a cast from from_ty to to_ty is valid, returns a Some containing the kind of the cast.
index_operand_ambiguity_span 🔒
make_invalid_casting_error 🔒