pub enum ExprKind<'hir> {
Show 32 variants Box(&'hir Expr<'hir>), ConstBlock(AnonConst), Array(&'hir [Expr<'hir>]), Call(&'hir Expr<'hir>, &'hir [Expr<'hir>]), MethodCall(&'hir PathSegment<'hir>, &'hir [Expr<'hir>]Span), Tup(&'hir [Expr<'hir>]), Binary(BinOp, &'hir Expr<'hir>, &'hir Expr<'hir>), Unary(UnOp, &'hir Expr<'hir>), Lit(Lit), Cast(&'hir Expr<'hir>, &'hir Ty<'hir>), Type(&'hir Expr<'hir>, &'hir Ty<'hir>), DropTemps(&'hir Expr<'hir>), Let(&'hir Let<'hir>), If(&'hir Expr<'hir>, &'hir Expr<'hir>, Option<&'hir Expr<'hir>>), Loop(&'hir Block<'hir>, Option<Label>, LoopSourceSpan), Match(&'hir Expr<'hir>, &'hir [Arm<'hir>]MatchSource), Closure(CaptureBy, &'hir FnDecl<'hir>, BodyIdSpanOption<Movability>), Block(&'hir Block<'hir>, Option<Label>), Assign(&'hir Expr<'hir>, &'hir Expr<'hir>, Span), AssignOp(BinOp, &'hir Expr<'hir>, &'hir Expr<'hir>), Field(&'hir Expr<'hir>, Ident), Index(&'hir Expr<'hir>, &'hir Expr<'hir>), Path(QPath<'hir>), AddrOf(BorrowKindMutability, &'hir Expr<'hir>), Break(DestinationOption<&'hir Expr<'hir>>), Continue(Destination), Ret(Option<&'hir Expr<'hir>>), InlineAsm(&'hir InlineAsm<'hir>), Struct(&'hir QPath<'hir>, &'hir [ExprField<'hir>]Option<&'hir Expr<'hir>>), Repeat(&'hir Expr<'hir>, ArrayLen), Yield(&'hir Expr<'hir>, YieldSource), Err,


Box(&'hir Expr<'hir>)

A box x expression.


Allow anonymous constants from an inline const block

Array(&'hir [Expr<'hir>])

An array (e.g., [a, b, c, d]).

Call(&'hir Expr<'hir>, &'hir [Expr<'hir>])

A function call.

The first field resolves to the function itself (usually an ExprKind::Path), and the second field is the list of arguments. This also represents calling the constructor of tuple-like ADTs such as tuple structs and enum variants.

MethodCall(&'hir PathSegment<'hir>, &'hir [Expr<'hir>]Span)

A method call (e.g.,<'static, Bar, Baz>(a, b, c, d)).

The PathSegment represents the method name and its generic arguments (within the angle brackets). The first element of the &[Expr] is the expression that evaluates to the object on which the method is being called on (the receiver), and the remaining elements are the rest of the arguments. Thus,<Bar, Baz>(a, b, c, d) is represented as ExprKind::MethodCall(PathSegment { foo, [Bar, Baz] }, [x, a, b, c, d], span). The final Span represents the span of the function and arguments (e.g. foo::<Bar, Baz>(a, b, c, d) in<Bar, Baz>(a, b, c, d)

To resolve the called method to a DefId, call type_dependent_def_id with the hir_id of the MethodCall node itself.

Tup(&'hir [Expr<'hir>])

A tuple (e.g., (a, b, c, d)).

Binary(BinOp, &'hir Expr<'hir>, &'hir Expr<'hir>)

A binary operation (e.g., a + b, a * b).

Unary(UnOp, &'hir Expr<'hir>)

A unary operation (e.g., !x, *x).


A literal (e.g., 1, "foo").

Cast(&'hir Expr<'hir>, &'hir Ty<'hir>)

A cast (e.g., foo as f64).

Type(&'hir Expr<'hir>, &'hir Ty<'hir>)

A type reference (e.g., Foo).

DropTemps(&'hir Expr<'hir>)

Wraps the expression in a terminating scope. This makes it semantically equivalent to { let _t = expr; _t }.

This construct only exists to tweak the drop order in HIR lowering. An example of that is the desugaring of for loops.

Let(&'hir Let<'hir>)

A let $pat = $expr expression.

These are not Local and only occur as expressions. The let Some(x) = foo() in if let Some(x) = foo() is an example of Let(..).

If(&'hir Expr<'hir>, &'hir Expr<'hir>, Option<&'hir Expr<'hir>>)

An if block, with an optional else block.

I.e., if <expr> { <expr> } else { <expr> }.

Loop(&'hir Block<'hir>, Option<Label>, LoopSourceSpan)

A conditionless loop (can be exited with break, continue, or return).

I.e., 'label: loop { <block> }.

The Span is the loop header (for x in y/while let pat = expr).

Match(&'hir Expr<'hir>, &'hir [Arm<'hir>]MatchSource)

A match block, with a source that indicates whether or not it is the result of a desugaring, and if so, which kind.

Closure(CaptureBy, &'hir FnDecl<'hir>, BodyIdSpanOption<Movability>)

A closure (e.g., move |a, b, c| {a + b + c}).

The Span is the argument block |...|.

This may also be a generator literal or an async block as indicated by the Option<Movability>.

Block(&'hir Block<'hir>, Option<Label>)

A block (e.g., 'label: { ... }).

Assign(&'hir Expr<'hir>, &'hir Expr<'hir>, Span)

An assignment (e.g., a = foo()).

AssignOp(BinOp, &'hir Expr<'hir>, &'hir Expr<'hir>)

An assignment with an operator.

E.g., a += 1.

Field(&'hir Expr<'hir>, Ident)

Access of a named (e.g., or unnamed (e.g., obj.0) struct or tuple field.

Index(&'hir Expr<'hir>, &'hir Expr<'hir>)

An indexing operation (foo[2]).


Path to a definition, possibly containing lifetime or type parameters.

AddrOf(BorrowKindMutability, &'hir Expr<'hir>)

A referencing operation (i.e., &a or &mut a).

Break(DestinationOption<&'hir Expr<'hir>>)

A break, with an optional label to break.


A continue, with an optional label.

Ret(Option<&'hir Expr<'hir>>)

A return, with an optional value to be returned.

InlineAsm(&'hir InlineAsm<'hir>)

Inline assembly (from asm!), with its outputs and inputs.

Struct(&'hir QPath<'hir>, &'hir [ExprField<'hir>]Option<&'hir Expr<'hir>>)

A struct or struct-like variant literal expression.

E.g., Foo {x: 1, y: 2}, or Foo {x: 1, .. base}, where base is the Option<Expr>.

Repeat(&'hir Expr<'hir>, ArrayLen)

An array literal constructed from one repeated element.

E.g., [1; 5]. The first expression is the element to be repeated; the second is the number of times to repeat it.

Yield(&'hir Expr<'hir>, YieldSource)

A suspension point for generators (i.e., yield <expr>).


A placeholder for an expression that wasn’t syntactically well formed in some way.

Trait Implementations

Formats the value using the given formatter. Read more

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more

Immutably borrows from an owned value. Read more

Mutably borrows from an owned value. Read more

Returns the argument unchanged.

Calls U::from(self).

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

The type returned in the event of a conversion error.

Performs the conversion.

The type returned in the event of a conversion error.

Performs the conversion.


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: 40 bytes

Size for each variant:

  • Box: 15 bytes
  • ConstBlock: 19 bytes
  • Array: 23 bytes
  • Call: 31 bytes
  • MethodCall: 39 bytes
  • Tup: 23 bytes
  • Binary: 31 bytes
  • Unary: 15 bytes
  • Lit: 39 bytes
  • Cast: 23 bytes
  • Type: 23 bytes
  • DropTemps: 15 bytes
  • Let: 15 bytes
  • If: 31 bytes
  • Loop: 31 bytes
  • Match: 31 bytes
  • Closure: 31 bytes
  • Block: 23 bytes
  • Assign: 31 bytes
  • AssignOp: 31 bytes
  • Field: 23 bytes
  • Index: 23 bytes
  • Path: 31 bytes
  • AddrOf: 15 bytes
  • Break: 39 bytes
  • Continue: 27 bytes
  • Ret: 15 bytes
  • InlineAsm: 15 bytes
  • Struct: 39 bytes
  • Repeat: 31 bytes
  • Yield: 23 bytes
  • Err: 0 bytes