struct TopInfo<'tcx> {
    expected: Ty<'tcx>,
    origin_expr: Option<&'tcx Expr<'tcx>>,
    span: Option<Span>,
}
Expand description

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!

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§expected: Ty<'tcx>

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

§origin_expr: Option<&'tcx Expr<'tcx>>

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<_, _>`

Trait Implementations§

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

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

Returns a copy of the value. Read more
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fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl<'tcx> Copy for TopInfo<'tcx>

Auto Trait Implementations§

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impl<'tcx> !RefUnwindSafe for TopInfo<'tcx>

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impl<'tcx> !Send for TopInfo<'tcx>

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impl<'tcx> !Sync for TopInfo<'tcx>

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impl<'tcx> Unpin for TopInfo<'tcx>

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impl<'tcx> !UnwindSafe for TopInfo<'tcx>

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impl<T> Any for Twhere T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for Twhere T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for Twhere T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into<U> for Twhere U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<T> ToOwned for Twhere T: Clone,

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type Owned = T

The resulting type after obtaining ownership.
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fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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impl<T, U> TryFrom<U> for Twhere U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for Twhere U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.

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