Struct flexi_parse::group::Group

source · 
pub struct Group<D: Delimiters> { /* private fields */ }
Expand description

A delimited group.

For more information, see the module documentation.

Implementations§

source§

impl<D: Delimiters> Group<D>

source

pub fn into_token_stream(self) -> TokenStream

Returns the contained TokenStream.

Examples found in repository?
examples/calc.rs (line 90)
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fn primary(input: ParseStream<'_>) -> Result<Expr> {
    let lookahead = input.lookahead();
    if lookahead.peek(token::LitFloat) {
        Ok(Expr::Num(input.parse::<token::LitFloat>()?.value()))
    } else if lookahead.peek(token::LitInt) {
        Ok(Expr::Num(input.parse::<token::LitInt>()?.value() as f64))
    } else if lookahead.peek(token::LeftParen) {
        let group: Group<Parentheses> = input.parse()?;
        parse(group.into_token_stream())
    } else {
        Err(lookahead.error())
    }
}
More examples
Hide additional examples
examples/lox/main.rs (line 360)
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    fn finish_call(input: ParseStream<'_>, callee: Expr) -> Result<Self> {
        let mut contents: Group<Parentheses> = input.parse()?;
        contents.remove_whitespace();
        let paren = contents.delimiters();
        let arguments: Punctuated<Expr, Punct![","]> =
            Punctuated::parse_separated_trailing.parse(contents.into_token_stream())?;
        let arguments: Vec<_> = arguments.into_iter().collect();
        if arguments.len() >= 255 {
            input.add_error(input.new_error(
                "Can't have more than 254 arguments".to_string(),
                paren.0.clone(),
                error_codes::TOO_MANY_ARGS,
            ));
        }
        Ok(Expr::Call {
            callee: Box::new(callee),
            paren,
            arguments,
        })
    }

    fn primary(input: ParseStream<'_>) -> Result<Self> {
        let lookahead = input.lookahead();
        if lookahead.peek(kw::keyword_false) {
            Ok(Expr::Literal(Literal::False(input.parse()?)))
        } else if lookahead.peek(kw::keyword_true) {
            Ok(Expr::Literal(Literal::True(input.parse()?)))
        } else if lookahead.peek(kw::keyword_nil) {
            Ok(Expr::Literal(Literal::Nil(input.parse()?)))
        } else if lookahead.peek(LitFloat) {
            Ok(Expr::Literal(Literal::Float(input.parse()?)))
        } else if lookahead.peek(LitInt) {
            Ok(Expr::Literal(Literal::Int(input.parse()?)))
        } else if lookahead.peek(LitStr) {
            Ok(Expr::Literal(Literal::String(input.parse()?)))
        } else if input.peek(kw::keyword_super) {
            Ok(Expr::Super {
                keyword: input.parse()?,
                distance: Cell::new(None),
                dot: input.parse()?,
                method: input.parse()?,
            })
        } else if input.peek(kw::keyword_this) {
            Ok(Expr::This {
                keyword: input.parse()?,
                distance: Cell::new(None),
            })
        } else if lookahead.peek(Ident) {
            Ok(Expr::Variable {
                name: kw::ident(input)?,
                distance: Cell::new(None),
            })
        } else if lookahead.peek(Punct!["("]) {
            let group: Group<Parentheses> = input.parse()?;
            Ok(Expr::Group(Box::new(parse(group.into_token_stream())?)))
        } else {
            Err(lookahead.error())
        }
    }
}

impl Parse for Expr {
    fn parse(input: ParseStream<'_>) -> Result<Self> {
        Expr::assignment(input)
    }
}

#[derive(Debug, Clone, PartialEq)]
struct Function {
    name: Ident,
    params: Vec<Ident>,
    body: Vec<Stmt>,
}

impl Parse for Function {
    fn parse(input: ParseStream<'_>) -> Result<Self> {
        let name: Ident = input.parse()?;
        let mut contents: Group<Parentheses> = input.parse()?;
        contents.remove_whitespace();
        let Parentheses(span) = contents.delimiters();
        let tokens = contents.into_token_stream();
        let params: Vec<Ident> = if tokens.is_empty() {
            vec![]
        } else {
            let params: Punctuated<Ident, Punct![","]> =
                Punctuated::parse_separated.parse(tokens)?;
            params.into_iter().collect()
        };
        if params.len() >= 255 {
            input.add_error(input.new_error(
                "Can't have more than 254 parameters".to_string(),
                span,
                error_codes::TOO_MANY_ARGS,
            ));
        }
        let mut contents: Group<Braces> = input.parse()?;
        contents.remove_whitespace();
        let body = block.parse(contents.into_token_stream())?;
        Ok(Function { name, params, body })
    }
}

#[derive(Debug, Clone, PartialEq)]
enum Stmt {
    Block(Vec<Stmt>),
    Class {
        name: Ident,
        superclass: Option<Ident>,
        superclass_distance: Cell<Option<usize>>,
        methods: Vec<Function>,
    },
    Expr(Expr),
    Function(Function),
    If {
        condition: Expr,
        then_branch: Box<Stmt>,
        else_branch: Option<Box<Stmt>>,
    },
    Print(Expr),
    Return {
        keyword: kw::keyword_return,
        value: Option<Expr>,
    },
    Variable {
        name: Ident,
        initialiser: Option<Expr>,
    },
    While {
        condition: Expr,
        body: Box<Stmt>,
    },
}

fn block(input: ParseStream<'_>) -> Result<Vec<Stmt>> {
    let mut statements = vec![];

    while !input.is_empty() {
        statements.push(Stmt::declaration(input)?);
    }

    Ok(statements)
}

impl Stmt {
    fn declaration(input: ParseStream<'_>) -> Result<Self> {
        if input.peek(kw::keyword_class) {
            Stmt::class_declaration(input)
        } else if input.peek(kw::keyword_fun) {
            let _: kw::keyword_fun = input.parse()?;
            Ok(Stmt::Function(Function::parse(input)?))
        } else if input.peek(kw::keyword_var) {
            Stmt::var_declaration(input)
        } else {
            Stmt::statement(input)
        }
    }

    fn class_declaration(input: ParseStream<'_>) -> Result<Self> {
        let _: kw::keyword_class = input.parse()?;
        let name: Ident = input.parse()?;

        let superclass = if input.peek(Punct!["<"]) {
            let _: Punct!["<"] = input.parse()?;
            Some(input.parse()?)
        } else {
            None
        };

        let mut contents: Group<Braces> = input.parse()?;
        contents.remove_whitespace();
        let methods = parse_repeated.parse(contents.into_token_stream())?;

        Ok(Stmt::Class {
            name,
            superclass,
            superclass_distance: Cell::new(None),
            methods,
        })
    }

    fn var_declaration(input: ParseStream<'_>) -> Result<Self> {
        let _: kw::keyword_var = input.parse()?;

        let name = kw::ident(input)?;

        let initialiser = if input.peek(Punct!["="]) {
            let _: Punct!["="] = input.parse()?;
            Some(input.parse()?)
        } else {
            None
        };

        let _: Punct![";"] = input.parse()?;
        Ok(Stmt::Variable { name, initialiser })
    }

    fn statement(input: ParseStream<'_>) -> Result<Self> {
        if input.peek(kw::keyword_if) {
            Stmt::if_statement(input)
        } else if input.peek(kw::keyword_for) {
            Stmt::for_statement(input)
        } else if input.peek(kw::keyword_print) {
            Stmt::print_statement(input)
        } else if input.peek(kw::keyword_return) {
            Stmt::return_statement(input)
        } else if input.peek(kw::keyword_while) {
            Stmt::while_statement(input)
        } else if input.peek(Punct!["{"]) {
            let mut group: Group<Braces> = input.parse()?;
            group.remove_whitespace();
            Ok(Stmt::Block(block.parse(group.into_token_stream())?))
        } else {
            Stmt::expression_statement(input)
        }
    }

    fn for_statement(input: ParseStream<'_>) -> Result<Self> {
        struct ForInner(Option<Stmt>, Expr, Option<Expr>);

        impl Parse for ForInner {
            fn parse(input: ParseStream<'_>) -> Result<Self> {
                let initialiser = if input.peek(Punct![";"]) {
                    let _: Punct![";"] = input.parse()?;
                    None
                } else if input.peek(kw::keyword_var) {
                    Some(Stmt::var_declaration(input)?)
                } else {
                    Some(Stmt::expression_statement(input)?)
                };

                let condition = if input.peek(Punct![";"]) {
                    Expr::Literal(Literal::True(kw::keyword_true::new(input)))
                } else {
                    Expr::parse(input)?
                };
                let _: Punct![";"] = input.parse()?;

                let increment = if input.is_empty() {
                    None
                } else {
                    Some(Expr::parse(input)?)
                };

                Ok(ForInner(initialiser, condition, increment))
            }
        }

        let _: kw::keyword_for = input.parse()?;

        let mut inner: Group<Parentheses> = input.parse()?;
        inner.remove_whitespace();
        let ForInner(initialiser, condition, increment) = parse(inner.into_token_stream())?;

        let mut body = Stmt::statement(input)?;

        if let Some(increment) = increment {
            body = Stmt::Block(vec![body, Stmt::Expr(increment)]);
        }

        body = Stmt::While {
            condition,
            body: Box::new(body),
        };

        if let Some(initialiser) = initialiser {
            body = Stmt::Block(vec![initialiser, body]);
        }

        Ok(body)
    }

    fn if_statement(input: ParseStream<'_>) -> Result<Self> {
        let _: kw::keyword_if = input.parse()?;
        let condition: Group<Parentheses> = input.parse()?;
        let condition = parse(condition.into_token_stream())?;

        let then_branch = Box::new(Stmt::statement(input)?);
        let else_branch = if input.peek(kw::keyword_else) {
            Some(Box::new(Stmt::statement(input)?))
        } else {
            None
        };

        Ok(Stmt::If {
            condition,
            then_branch,
            else_branch,
        })
    }

    fn print_statement(input: ParseStream<'_>) -> Result<Self> {
        let _: kw::keyword_print = input.parse()?;
        let value = input.parse()?;
        let _: Punct![";"] = input.parse()?;
        Ok(Self::Print(value))
    }

    fn return_statement(input: ParseStream<'_>) -> Result<Self> {
        let keyword: kw::keyword_return = input.parse()?;
        let value = if input.peek(Punct![";"]) {
            None
        } else {
            Some(input.parse()?)
        };
        let _: Punct![";"] = input.parse()?;
        Ok(Stmt::Return { keyword, value })
    }

    fn while_statement(input: ParseStream<'_>) -> Result<Self> {
        let _: kw::keyword_while = input.parse()?;
        let condition: Group<Parentheses> = input.parse()?;
        let condition = parse(condition.into_token_stream())?;
        let body = Box::new(Stmt::statement(input)?);

        Ok(Stmt::While { condition, body })
    }
source

pub fn delimiters(&self) -> D

Returns a token representing the delimiters of this group.

Examples found in repository?
examples/lox/main.rs (line 358)
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    fn finish_call(input: ParseStream<'_>, callee: Expr) -> Result<Self> {
        let mut contents: Group<Parentheses> = input.parse()?;
        contents.remove_whitespace();
        let paren = contents.delimiters();
        let arguments: Punctuated<Expr, Punct![","]> =
            Punctuated::parse_separated_trailing.parse(contents.into_token_stream())?;
        let arguments: Vec<_> = arguments.into_iter().collect();
        if arguments.len() >= 255 {
            input.add_error(input.new_error(
                "Can't have more than 254 arguments".to_string(),
                paren.0.clone(),
                error_codes::TOO_MANY_ARGS,
            ));
        }
        Ok(Expr::Call {
            callee: Box::new(callee),
            paren,
            arguments,
        })
    }

    fn primary(input: ParseStream<'_>) -> Result<Self> {
        let lookahead = input.lookahead();
        if lookahead.peek(kw::keyword_false) {
            Ok(Expr::Literal(Literal::False(input.parse()?)))
        } else if lookahead.peek(kw::keyword_true) {
            Ok(Expr::Literal(Literal::True(input.parse()?)))
        } else if lookahead.peek(kw::keyword_nil) {
            Ok(Expr::Literal(Literal::Nil(input.parse()?)))
        } else if lookahead.peek(LitFloat) {
            Ok(Expr::Literal(Literal::Float(input.parse()?)))
        } else if lookahead.peek(LitInt) {
            Ok(Expr::Literal(Literal::Int(input.parse()?)))
        } else if lookahead.peek(LitStr) {
            Ok(Expr::Literal(Literal::String(input.parse()?)))
        } else if input.peek(kw::keyword_super) {
            Ok(Expr::Super {
                keyword: input.parse()?,
                distance: Cell::new(None),
                dot: input.parse()?,
                method: input.parse()?,
            })
        } else if input.peek(kw::keyword_this) {
            Ok(Expr::This {
                keyword: input.parse()?,
                distance: Cell::new(None),
            })
        } else if lookahead.peek(Ident) {
            Ok(Expr::Variable {
                name: kw::ident(input)?,
                distance: Cell::new(None),
            })
        } else if lookahead.peek(Punct!["("]) {
            let group: Group<Parentheses> = input.parse()?;
            Ok(Expr::Group(Box::new(parse(group.into_token_stream())?)))
        } else {
            Err(lookahead.error())
        }
    }
}

impl Parse for Expr {
    fn parse(input: ParseStream<'_>) -> Result<Self> {
        Expr::assignment(input)
    }
}

#[derive(Debug, Clone, PartialEq)]
struct Function {
    name: Ident,
    params: Vec<Ident>,
    body: Vec<Stmt>,
}

impl Parse for Function {
    fn parse(input: ParseStream<'_>) -> Result<Self> {
        let name: Ident = input.parse()?;
        let mut contents: Group<Parentheses> = input.parse()?;
        contents.remove_whitespace();
        let Parentheses(span) = contents.delimiters();
        let tokens = contents.into_token_stream();
        let params: Vec<Ident> = if tokens.is_empty() {
            vec![]
        } else {
            let params: Punctuated<Ident, Punct![","]> =
                Punctuated::parse_separated.parse(tokens)?;
            params.into_iter().collect()
        };
        if params.len() >= 255 {
            input.add_error(input.new_error(
                "Can't have more than 254 parameters".to_string(),
                span,
                error_codes::TOO_MANY_ARGS,
            ));
        }
        let mut contents: Group<Braces> = input.parse()?;
        contents.remove_whitespace();
        let body = block.parse(contents.into_token_stream())?;
        Ok(Function { name, params, body })
    }
source

pub fn remove_whitespace(&mut self)

Removes whitespace from the tokenstream in self.

Examples found in repository?
examples/lox/main.rs (line 357)
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    fn finish_call(input: ParseStream<'_>, callee: Expr) -> Result<Self> {
        let mut contents: Group<Parentheses> = input.parse()?;
        contents.remove_whitespace();
        let paren = contents.delimiters();
        let arguments: Punctuated<Expr, Punct![","]> =
            Punctuated::parse_separated_trailing.parse(contents.into_token_stream())?;
        let arguments: Vec<_> = arguments.into_iter().collect();
        if arguments.len() >= 255 {
            input.add_error(input.new_error(
                "Can't have more than 254 arguments".to_string(),
                paren.0.clone(),
                error_codes::TOO_MANY_ARGS,
            ));
        }
        Ok(Expr::Call {
            callee: Box::new(callee),
            paren,
            arguments,
        })
    }

    fn primary(input: ParseStream<'_>) -> Result<Self> {
        let lookahead = input.lookahead();
        if lookahead.peek(kw::keyword_false) {
            Ok(Expr::Literal(Literal::False(input.parse()?)))
        } else if lookahead.peek(kw::keyword_true) {
            Ok(Expr::Literal(Literal::True(input.parse()?)))
        } else if lookahead.peek(kw::keyword_nil) {
            Ok(Expr::Literal(Literal::Nil(input.parse()?)))
        } else if lookahead.peek(LitFloat) {
            Ok(Expr::Literal(Literal::Float(input.parse()?)))
        } else if lookahead.peek(LitInt) {
            Ok(Expr::Literal(Literal::Int(input.parse()?)))
        } else if lookahead.peek(LitStr) {
            Ok(Expr::Literal(Literal::String(input.parse()?)))
        } else if input.peek(kw::keyword_super) {
            Ok(Expr::Super {
                keyword: input.parse()?,
                distance: Cell::new(None),
                dot: input.parse()?,
                method: input.parse()?,
            })
        } else if input.peek(kw::keyword_this) {
            Ok(Expr::This {
                keyword: input.parse()?,
                distance: Cell::new(None),
            })
        } else if lookahead.peek(Ident) {
            Ok(Expr::Variable {
                name: kw::ident(input)?,
                distance: Cell::new(None),
            })
        } else if lookahead.peek(Punct!["("]) {
            let group: Group<Parentheses> = input.parse()?;
            Ok(Expr::Group(Box::new(parse(group.into_token_stream())?)))
        } else {
            Err(lookahead.error())
        }
    }
}

impl Parse for Expr {
    fn parse(input: ParseStream<'_>) -> Result<Self> {
        Expr::assignment(input)
    }
}

#[derive(Debug, Clone, PartialEq)]
struct Function {
    name: Ident,
    params: Vec<Ident>,
    body: Vec<Stmt>,
}

impl Parse for Function {
    fn parse(input: ParseStream<'_>) -> Result<Self> {
        let name: Ident = input.parse()?;
        let mut contents: Group<Parentheses> = input.parse()?;
        contents.remove_whitespace();
        let Parentheses(span) = contents.delimiters();
        let tokens = contents.into_token_stream();
        let params: Vec<Ident> = if tokens.is_empty() {
            vec![]
        } else {
            let params: Punctuated<Ident, Punct![","]> =
                Punctuated::parse_separated.parse(tokens)?;
            params.into_iter().collect()
        };
        if params.len() >= 255 {
            input.add_error(input.new_error(
                "Can't have more than 254 parameters".to_string(),
                span,
                error_codes::TOO_MANY_ARGS,
            ));
        }
        let mut contents: Group<Braces> = input.parse()?;
        contents.remove_whitespace();
        let body = block.parse(contents.into_token_stream())?;
        Ok(Function { name, params, body })
    }
}

#[derive(Debug, Clone, PartialEq)]
enum Stmt {
    Block(Vec<Stmt>),
    Class {
        name: Ident,
        superclass: Option<Ident>,
        superclass_distance: Cell<Option<usize>>,
        methods: Vec<Function>,
    },
    Expr(Expr),
    Function(Function),
    If {
        condition: Expr,
        then_branch: Box<Stmt>,
        else_branch: Option<Box<Stmt>>,
    },
    Print(Expr),
    Return {
        keyword: kw::keyword_return,
        value: Option<Expr>,
    },
    Variable {
        name: Ident,
        initialiser: Option<Expr>,
    },
    While {
        condition: Expr,
        body: Box<Stmt>,
    },
}

fn block(input: ParseStream<'_>) -> Result<Vec<Stmt>> {
    let mut statements = vec![];

    while !input.is_empty() {
        statements.push(Stmt::declaration(input)?);
    }

    Ok(statements)
}

impl Stmt {
    fn declaration(input: ParseStream<'_>) -> Result<Self> {
        if input.peek(kw::keyword_class) {
            Stmt::class_declaration(input)
        } else if input.peek(kw::keyword_fun) {
            let _: kw::keyword_fun = input.parse()?;
            Ok(Stmt::Function(Function::parse(input)?))
        } else if input.peek(kw::keyword_var) {
            Stmt::var_declaration(input)
        } else {
            Stmt::statement(input)
        }
    }

    fn class_declaration(input: ParseStream<'_>) -> Result<Self> {
        let _: kw::keyword_class = input.parse()?;
        let name: Ident = input.parse()?;

        let superclass = if input.peek(Punct!["<"]) {
            let _: Punct!["<"] = input.parse()?;
            Some(input.parse()?)
        } else {
            None
        };

        let mut contents: Group<Braces> = input.parse()?;
        contents.remove_whitespace();
        let methods = parse_repeated.parse(contents.into_token_stream())?;

        Ok(Stmt::Class {
            name,
            superclass,
            superclass_distance: Cell::new(None),
            methods,
        })
    }

    fn var_declaration(input: ParseStream<'_>) -> Result<Self> {
        let _: kw::keyword_var = input.parse()?;

        let name = kw::ident(input)?;

        let initialiser = if input.peek(Punct!["="]) {
            let _: Punct!["="] = input.parse()?;
            Some(input.parse()?)
        } else {
            None
        };

        let _: Punct![";"] = input.parse()?;
        Ok(Stmt::Variable { name, initialiser })
    }

    fn statement(input: ParseStream<'_>) -> Result<Self> {
        if input.peek(kw::keyword_if) {
            Stmt::if_statement(input)
        } else if input.peek(kw::keyword_for) {
            Stmt::for_statement(input)
        } else if input.peek(kw::keyword_print) {
            Stmt::print_statement(input)
        } else if input.peek(kw::keyword_return) {
            Stmt::return_statement(input)
        } else if input.peek(kw::keyword_while) {
            Stmt::while_statement(input)
        } else if input.peek(Punct!["{"]) {
            let mut group: Group<Braces> = input.parse()?;
            group.remove_whitespace();
            Ok(Stmt::Block(block.parse(group.into_token_stream())?))
        } else {
            Stmt::expression_statement(input)
        }
    }

    fn for_statement(input: ParseStream<'_>) -> Result<Self> {
        struct ForInner(Option<Stmt>, Expr, Option<Expr>);

        impl Parse for ForInner {
            fn parse(input: ParseStream<'_>) -> Result<Self> {
                let initialiser = if input.peek(Punct![";"]) {
                    let _: Punct![";"] = input.parse()?;
                    None
                } else if input.peek(kw::keyword_var) {
                    Some(Stmt::var_declaration(input)?)
                } else {
                    Some(Stmt::expression_statement(input)?)
                };

                let condition = if input.peek(Punct![";"]) {
                    Expr::Literal(Literal::True(kw::keyword_true::new(input)))
                } else {
                    Expr::parse(input)?
                };
                let _: Punct![";"] = input.parse()?;

                let increment = if input.is_empty() {
                    None
                } else {
                    Some(Expr::parse(input)?)
                };

                Ok(ForInner(initialiser, condition, increment))
            }
        }

        let _: kw::keyword_for = input.parse()?;

        let mut inner: Group<Parentheses> = input.parse()?;
        inner.remove_whitespace();
        let ForInner(initialiser, condition, increment) = parse(inner.into_token_stream())?;

        let mut body = Stmt::statement(input)?;

        if let Some(increment) = increment {
            body = Stmt::Block(vec![body, Stmt::Expr(increment)]);
        }

        body = Stmt::While {
            condition,
            body: Box::new(body),
        };

        if let Some(initialiser) = initialiser {
            body = Stmt::Block(vec![initialiser, body]);
        }

        Ok(body)
    }

Trait Implementations§

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impl<D: Clone + Delimiters> Clone for Group<D>

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fn clone(&self) -> Group<D>

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<D: Debug + Delimiters> Debug for Group<D>

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fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more
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impl<D: Delimiters> Parse for Group<D>

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fn parse(input: ParseStream<'_>) -> Result<Self>

Parses the input into this type.

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impl<D> RefUnwindSafe for Group<D>where D: RefUnwindSafe,

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impl<D> !Send for Group<D>

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impl<D> !Sync for Group<D>

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impl<D> Unpin for Group<D>where D: Unpin,

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impl<D> UnwindSafe for Group<D>where D: UnwindSafe,

Blanket Implementations§

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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.