# Struct syn::parse::StepCursor [−] [src]

    pub struct StepCursor<'c, 'a> { /* fields omitted */ }

Cursor state associated with speculative parsing.

This type is the input of the closure provided to `ParseStream::step`.

# Example

    use proc_macro2::TokenTree;
    use syn::Result;
    use syn::parse::ParseStream;

    // This function advances the stream past the next occurrence of `@`. If
    // no `@` is present in the stream, the stream position is unchanged and
    // an error is returned.
    fn skip_past_next_at(input: ParseStream) -> Result<()> {
        input.step(|cursor| {
            let mut rest = *cursor;
            while let Some((tt, next)) = rest.token_tree() {
                match &tt {
                    TokenTree::Punct(punct) if punct.as_char() == '@' => {
                        return Ok(((), next));
                    }
                    _ => rest = next,
                }
            }
            Err(cursor.error("no `@` was found after this point"))
        })
    }

## Implementations

### `impl<'c, 'a> StepCursor<'c, 'a>` [src]

#### `pub fn error<T: Display>(self, message: T) -> Error` [src]

Triggers an error at the current position of the parse stream.

The `ParseStream::step` invocation will return this same error without advancing the stream state.

## Methods from Deref<Target = Cursor<'c>>

## Trait Implementations

### `impl<'c, 'a> Clone for StepCursor<'c, 'a>` [src]

#### `fn clone(&self) -> Self` [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<'c, 'a> Copy for StepCursor<'c, 'a>` [src]

### `impl<'c, 'a> Deref for StepCursor<'c, 'a>` [src]

#### `type Target = Cursor<'c>`

The resulting type after dereferencing.

#### `fn deref(&self) -> &Self::Target` [src]

Dereferences the value.

## Auto Trait Implementations

### `impl<'c, 'a> RefUnwindSafe for StepCursor<'c, 'a>`

### `impl<'c, 'a> !Send for StepCursor<'c, 'a>`

### `impl<'c, 'a> !Sync for StepCursor<'c, 'a>`

### `impl<'c, 'a> Unpin for StepCursor<'c, 'a>`

### `impl<'c, 'a> UnwindSafe for StepCursor<'c, 'a>`

## 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.