pub enum ExprKind {
Show 42 variants Box(P<Expr>), Array(Vec<P<Expr>>), ConstBlock(AnonConst), Call(P<Expr>, Vec<P<Expr>>), MethodCall(PathSegmentP<Expr>, Vec<P<Expr>>, Span), Tup(Vec<P<Expr>>), Binary(BinOpP<Expr>, P<Expr>), Unary(UnOpP<Expr>), Lit(Lit), Cast(P<Expr>, P<Ty>), Type(P<Expr>, P<Ty>), Let(P<Pat>, P<Expr>, Span), If(P<Expr>, P<Block>, Option<P<Expr>>), While(P<Expr>, P<Block>, Option<Label>), ForLoop(P<Pat>, P<Expr>, P<Block>, Option<Label>), Loop(P<Block>, Option<Label>), Match(P<Expr>, Vec<Arm>), Closure(ClosureBinderCaptureByAsyncMovabilityP<FnDecl>, P<Expr>, Span), Block(P<Block>, Option<Label>), Async(CaptureByNodeIdP<Block>), Await(P<Expr>), TryBlock(P<Block>), Assign(P<Expr>, P<Expr>, Span), AssignOp(BinOpP<Expr>, P<Expr>), Field(P<Expr>, Ident), Index(P<Expr>, P<Expr>), Range(Option<P<Expr>>, Option<P<Expr>>, RangeLimits), Underscore, Path(Option<QSelf>, Path), AddrOf(BorrowKindMutabilityP<Expr>), Break(Option<Label>, Option<P<Expr>>), Continue(Option<Label>), Ret(Option<P<Expr>>), InlineAsm(P<InlineAsm>), MacCall(P<MacCall>), Struct(P<StructExpr>), Repeat(P<Expr>, AnonConst), Paren(P<Expr>), Try(P<Expr>), Yield(Option<P<Expr>>), Yeet(Option<P<Expr>>), Err,



A box x expression.


An array ([a, b, c, d])


Allow anonymous constants from an inline const block

Call(P<Expr>, Vec<P<Expr>>)

A function call

The first field resolves to the function itself, 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(PathSegmentP<Expr>, Vec<P<Expr>>, Span)

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

The PathSegment represents the method name and its generic arguments (within the angle brackets). The standalone Expr is the receiver expression. The vector of Expr is the arguments.<Bar, Baz>(a, b, c, d) is represented as ExprKind::MethodCall(PathSegment { foo, [Bar, Baz] }, x, [a, b, c, d]). This Span is the span of the function, without the dot and receiver (e.g. foo(a, b) in, b)


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

Binary(BinOpP<Expr>, P<Expr>)

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


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


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

Cast(P<Expr>, P<Ty>)

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

Type(P<Expr>, P<Ty>)

A type ascription (e.g., 42: usize).

Let(P<Pat>, P<Expr>, Span)

A let pat = expr expression that is only semantically allowed in the condition of if / while expressions. (e.g., if let 0 = x { .. }).

Span represents the whole let pat = expr statement.

If(P<Expr>, P<Block>, Option<P<Expr>>)

An if block, with an optional else block.

if expr { block } else { expr }

While(P<Expr>, P<Block>, Option<Label>)

A while loop, with an optional label.

'label: while expr { block }

ForLoop(P<Pat>, P<Expr>, P<Block>, Option<Label>)

A for loop, with an optional label.

'label: for pat in expr { block }

This is desugared to a combination of loop and match expressions.

Loop(P<Block>, Option<Label>)

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

'label: loop { block }

Match(P<Expr>, Vec<Arm>)

A match block.

Closure(ClosureBinderCaptureByAsyncMovabilityP<FnDecl>, P<Expr>, Span)

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

The final span is the span of the argument block |...|.

Block(P<Block>, Option<Label>)

A block ('label: { ... }).


An async block (async move { ... }).

The NodeId is the NodeId for the closure that results from desugaring an async block, just like the NodeId field in the Async::Yes variant. This is necessary in order to create a def for the closure which can be used as a parent of any child defs. Defs created during lowering cannot be made the parent of any other preexisting defs.


An await expression (my_future.await).


A try block (try { ... }).

Assign(P<Expr>, P<Expr>, Span)

An assignment (a = foo()). The Span argument is the span of the = token.

AssignOp(BinOpP<Expr>, P<Expr>)

An assignment with an operator.

E.g., a += 1.

Field(P<Expr>, Ident)

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

Index(P<Expr>, P<Expr>)

An indexing operation (e.g., foo[2]).

Range(Option<P<Expr>>, Option<P<Expr>>, RangeLimits)

A range (e.g., 1..2, 1.., ..2, 1..=2, ..=2; and .. in destructuring assignment).


An underscore, used in destructuring assignment to ignore a value.

Path(Option<QSelf>, Path)

Variable reference, possibly containing :: and/or type parameters (e.g., foo::bar::<baz>).

Optionally “qualified” (e.g., <Vec<T> as SomeTrait>::SomeType).


A referencing operation (&a, &mut a, &raw const a or &raw mut a).

Break(Option<Label>, Option<P<Expr>>)

A break, with an optional label to break, and an optional expression.


A continue, with an optional label.


A return, with an optional value to be returned.


Output of the asm!() macro.


A macro invocation; pre-expansion.


A struct literal expression.

E.g., Foo {x: 1, y: 2}, or Foo {x: 1, .. rest}.

Repeat(P<Expr>, AnonConst)

An array literal constructed from one repeated element.

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


No-op: used solely so we can pretty-print faithfully.


A try expression (expr?).


A yield, with an optional value to be yielded.


A do yeet (aka throw/fail/bail/raise/whatever), with an optional value to be returned.


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

Trait Implementations

Returns a copy of the value. Read more
Performs copy-assignment from source. Read more
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 resulting type after obtaining ownership.
Creates owned data from borrowed data, usually by cloning. Read more
Uses borrowed data to replace owned data, usually by cloning. Read more
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: 72 bytes

Size for each variant:

  • Box: 15 bytes
  • Array: 31 bytes
  • ConstBlock: 23 bytes
  • Call: 39 bytes
  • MethodCall: 71 bytes
  • Tup: 31 bytes
  • Binary: 31 bytes
  • Unary: 15 bytes
  • Lit: 55 bytes
  • Cast: 23 bytes
  • Type: 23 bytes
  • Let: 31 bytes
  • If: 31 bytes
  • While: 31 bytes
  • ForLoop: 39 bytes
  • Loop: 23 bytes
  • Match: 39 bytes
  • Closure: 71 bytes
  • Block: 23 bytes
  • Async: 15 bytes
  • Await: 15 bytes
  • TryBlock: 15 bytes
  • Assign: 31 bytes
  • AssignOp: 31 bytes
  • Field: 23 bytes
  • Index: 23 bytes
  • Range: 23 bytes
  • Underscore: 0 bytes
  • Path: 71 bytes
  • AddrOf: 15 bytes
  • Break: 23 bytes
  • Continue: 15 bytes
  • Ret: 15 bytes
  • InlineAsm: 15 bytes
  • MacCall: 15 bytes
  • Struct: 15 bytes
  • Repeat: 31 bytes
  • Paren: 15 bytes
  • Try: 15 bytes
  • Yield: 15 bytes
  • Yeet: 15 bytes
  • Err: 0 bytes