# syn::ConstExpr - Rust
API documentation for the Rust `ConstExpr` enum in crate `syn`.
Keywords: rust, rustlang, rust-lang, ConstExpr

# [−] [src] Enum syn::ConstExpr

    pub enum ConstExpr {
        Call(Box<ConstExpr>, Vec<ConstExpr>),
        Binary(BinOp, Box<ConstExpr>, Box<ConstExpr>),
        Unary(UnOp, Box<ConstExpr>),
        Lit(Lit),
        Cast(Box<ConstExpr>, Box<Ty>),
        Path(Path),
        Index(Box<ConstExpr>, Box<ConstExpr>),
        Paren(Box<ConstExpr>),
        Other(Other),
    }

## Variants

`Call(Box<ConstExpr>, Vec<ConstExpr>)`

A function call

The first field resolves to the function itself, and the second field is the list of arguments

`Binary(BinOp, Box<ConstExpr>, Box<ConstExpr>)`

A binary operation (For example: `a + b`, `a * b`)

`Unary(UnOp, Box<ConstExpr>)`

A unary operation (For example: `!x`, `*x`)

`Lit(Lit)`

A literal (For example: `1`, `"foo"`)

`Cast(Box<ConstExpr>, Box<Ty>)`

A cast (`foo as f64`)

`Path(Path)`

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

`Index(Box<ConstExpr>, Box<ConstExpr>)`

An indexing operation (`foo[2]`)

`Paren(Box<ConstExpr>)`

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

`Other(Other)`

If compiling with full support for expression syntax, any expression is allowed

## Trait Implementations

### `impl Clone for ConstExpr` [src]

#### `fn clone(&self) -> ConstExpr` [src]

Returns a copy of the value. Read more

#### `pub fn clone_from(&mut self, source: &Self)`1.0.0 [src]

Performs copy-assignment from `source`. Read more

### `impl Debug for ConstExpr` [src]

#### `fn fmt(&self, f: &mut Formatter<'_>) -> Result` [src]

Formats the value using the given formatter. Read more

### `impl Eq for ConstExpr` [src]

### `impl Hash for ConstExpr` [src]

#### `fn hash<__H: Hasher>(&self, state: &mut __H)` [src]

Feeds this value into the given `Hasher`. Read more

#### `pub fn hash_slice<H>(data: &[Self], state: &mut H) where
H: Hasher,` 1.3.0 [src]

Feeds a slice of this type into the given `Hasher`. Read more

### `impl PartialEq<ConstExpr> for ConstExpr` [src]

#### `fn eq(&self, other: &ConstExpr) -> bool` [src]

This method tests for `self` and `other` values to be equal, and is used by `==`. Read more

#### `fn ne(&self, other: &ConstExpr) -> bool` [src]

This method tests for `!=`.

### `impl StructuralEq for ConstExpr` [src]

### `impl StructuralPartialEq for ConstExpr` [src]

### `impl ToTokens for ConstExpr` [src]

#### `fn to_tokens(&self, tokens: &mut Tokens)` [src]

Write `self` to the given `Tokens`. Read more

## Auto Trait Implementations

### `impl RefUnwindSafe for ConstExpr` [src]

### `impl Send for ConstExpr` [src]

### `impl Sync for ConstExpr` [src]

### `impl Unpin for ConstExpr` [src]

### `impl UnwindSafe for ConstExpr` [src]

## Blanket Implementations

### `impl<T> Any for T where
T: 'static + ?Sized,` [src]

#### `pub fn type_id(&self) -> TypeId` [src]

Gets the `TypeId` of `self`. Read more

### `impl<T> Borrow<T> for T where
T: ?Sized,` [src]

#### `pub fn borrow(&self) -> &T` [src]

Immutably borrows from an owned value. Read more

### `impl<T> BorrowMut<T> for T where
T: ?Sized,` [src]

#### `pub fn borrow_mut(&mut self) -> &mut T` [src]

Mutably borrows from an owned value. Read more

### `impl<T> From<T> for T` [src]

#### `pub fn from(t: T) -> T` [src]

Performs the conversion.

### `impl<T, U> Into<U> for T where
U: From<T>,` [src]

#### `pub fn into(self) -> U` [src]

Performs the conversion.

### `impl<T> ToOwned for T where
T: Clone,` [src]

#### `type Owned = T`

The resulting type after obtaining ownership.

#### `pub fn to_owned(&self) -> T` [src]

Creates owned data from borrowed data, usually by cloning. Read more

#### `pub fn clone_into(&self, target: &mut T)` [src]

🔬 This is a nightly-only experimental API. (`toowned_clone_into`)

recently added

Uses borrowed data to replace owned data, usually by cloning. Read more

### `impl<T, U> TryFrom<U> for T where
U: Into<T>,` [src]

#### `type Error = Infallible`

The type returned in the event of a conversion error.

#### `pub fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>` [src]

Performs the conversion.

### `impl<T, U> TryInto<U> for T where
U: TryFrom<T>,` [src]

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

The type returned in the event of a conversion error.

#### `pub fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>` [src]

Performs the conversion.