Struct rustc_typeck::check::pat::TopInfo

struct TopInfo<'tcx> {
    expected: Ty<'tcx>,
    origin_expr: bool,
    span: Option<Span>,
    parent_pat: Option<&'tcx Pat<'tcx>>,
}

Information about the expected type at the top level of type checking a pattern.

NOTE: This is only for use by diagnostics. Do NOT use for type checking logic!

Fields

expected: Ty<'tcx>

The expected type at the top level of type checking a pattern.

origin_expr: bool

Was the origin of the span from a scrutinee expression?

Otherwise there is no scrutinee and it could be e.g. from the type of a formal parameter.

span: Option<Span>

The span giving rise to the expected type, if one could be provided.

If origin_expr is true, then this is the span of the scrutinee as in:

• match scrutinee { ... }
• let _ = scrutinee;

This is used to point to add context in type errors. In the following example, span corresponds to the a + b expression:

error[E0308]: mismatched types
 --> src/main.rs:L:C
  |
L |    let temp: usize = match a + b {
  |                            ----- this expression has type `usize`
L |         Ok(num) => num,
  |         ^^^^^^^ expected `usize`, found enum `std::result::Result`
  |
  = note: expected type `usize`
             found type `std::result::Result<_, _>`

parent_pat: Option<&'tcx Pat<'tcx>>

This refers to the parent pattern. Used to provide extra diagnostic information on errors.

error[E0308]: mismatched types
  --> $DIR/const-in-struct-pat.rs:8:17
  |
L | struct f;
  | --------- unit struct defined here
...
L |     let Thing { f } = t;
  |                 ^
  |                 |
  |                 expected struct `std::string::String`, found struct `f`
  |                 `f` is interpreted as a unit struct, not a new binding
  |                 help: bind the struct field to a different name instead: `f: other_f`

Trait Implementations

impl<'tcx> Clone for TopInfo<'tcx>

fn clone(&self) -> TopInfo<'tcx>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<'tcx> Copy for TopInfo<'tcx>

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: 32 bytes