rust/src/types.rs

// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

use std::ops::Deref;
use std::iter::ExactSizeIterator;

use syntax::abi;
use syntax::ast::{self, Mutability, FunctionRetTy};
use syntax::codemap::{self, Span, BytePos};
use syntax::print::pprust;
use syntax::symbol::keywords;

use {Shape, Spanned};
use codemap::SpanUtils;
use lists::{format_item_list, itemize_list, format_fn_args};
use rewrite::{Rewrite, RewriteContext};
use utils::{extra_offset, format_mutability, colon_spaces, wrap_str};
use expr::{rewrite_unary_prefix, rewrite_pair, rewrite_tuple_type};
use config::TypeDensity;

#[derive(Copy, Clone, Debug, Eq, PartialEq)]
pub enum PathContext {
    Expr,
    Type,
    Import,
}

// Does not wrap on simple segments.
pub fn rewrite_path(context: &RewriteContext,
                    path_context: PathContext,
                    qself: Option<&ast::QSelf>,
                    path: &ast::Path,
                    shape: Shape)
                    -> Option<String> {
    let skip_count = qself.map_or(0, |x| x.position);

    let mut result = if path.is_global() && qself.is_none() &&
                        path_context != PathContext::Import {
        "::".to_owned()
    } else {
        String::new()
    };

    let mut span_lo = path.span.lo;

    if let Some(qself) = qself {
        result.push('<');
        if context.config.spaces_within_angle_brackets() {
            result.push_str(" ")
        }

        let fmt_ty = try_opt!(qself.ty.rewrite(context, shape));
        result.push_str(&fmt_ty);

        if skip_count > 0 {
            result.push_str(" as ");
            if path.is_global() && path_context != PathContext::Import {
                result.push_str("::");
            }

            let extra_offset = extra_offset(&result, shape);
            // 3 = ">::".len()
            let shape = try_opt!(try_opt!(shape.shrink_left(extra_offset)).sub_width(3));

            result = try_opt!(rewrite_path_segments(PathContext::Type,
                                                    result,
                                                    path.segments.iter().take(skip_count),
                                                    span_lo,
                                                    path.span.hi,
                                                    context,
                                                    shape));
        }

        if context.config.spaces_within_angle_brackets() {
            result.push_str(" ")
        }

        result.push_str(">::");
        span_lo = qself.ty.span.hi + BytePos(1);
    }

    rewrite_path_segments(path_context,
                          result,
                          path.segments.iter().skip(skip_count),
                          span_lo,
                          path.span.hi,
                          context,
                          shape)
}

fn rewrite_path_segments<'a, I>(path_context: PathContext,
                                mut buffer: String,
                                iter: I,
                                mut span_lo: BytePos,
                                span_hi: BytePos,
                                context: &RewriteContext,
                                shape: Shape)
                                -> Option<String>
    where I: Iterator<Item = &'a ast::PathSegment>
{
    let mut first = true;
    let shape = shape.visual_indent(0);

    for segment in iter {
        // Indicates a global path, shouldn't be rendered.
        if segment.identifier.name == keywords::CrateRoot.name() {
            continue;
        }
        if first {
            first = false;
        } else {
            buffer.push_str("::");
        }

        let extra_offset = extra_offset(&buffer, shape);
        let new_shape = try_opt!(shape.shrink_left(extra_offset));
        let segment_string = try_opt!(rewrite_segment(path_context,
                                                      segment,
                                                      &mut span_lo,
                                                      span_hi,
                                                      context,
                                                      new_shape));

        buffer.push_str(&segment_string);
    }

    Some(buffer)
}

#[derive(Debug)]
enum SegmentParam<'a> {
    LifeTime(&'a ast::Lifetime),
    Type(&'a ast::Ty),
    Binding(&'a ast::TypeBinding),
}

impl<'a> SegmentParam<'a> {
    fn get_span(&self) -> Span {
        match *self {
            SegmentParam::LifeTime(lt) => lt.span,
            SegmentParam::Type(ty) => ty.span,
            SegmentParam::Binding(binding) => binding.span,
        }
    }
}

impl<'a> Rewrite for SegmentParam<'a> {
    fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
        match *self {
            SegmentParam::LifeTime(lt) => lt.rewrite(context, shape),
            SegmentParam::Type(ty) => ty.rewrite(context, shape),
            SegmentParam::Binding(binding) => {
                let mut result = match context.config.type_punctuation_density() {
                    TypeDensity::Wide => format!("{} = ", binding.ident),
                    TypeDensity::Compressed => format!("{}=", binding.ident),
                };
                let budget = try_opt!(shape.width.checked_sub(result.len()));
                let rewrite = try_opt!(binding.ty.rewrite(context,
                                                          Shape::legacy(budget,
                                                                        shape.indent +
                                                                        result.len())));
                result.push_str(&rewrite);
                Some(result)
            }
        }
    }
}

// Formats a path segment. There are some hacks involved to correctly determine
// the segment's associated span since it's not part of the AST.
//
// The span_lo is assumed to be greater than the end of any previous segment's
// parameters and lesser or equal than the start of current segment.
//
// span_hi is assumed equal to the end of the entire path.
//
// When the segment contains a positive number of parameters, we update span_lo
// so that invariants described above will hold for the next segment.
fn rewrite_segment(path_context: PathContext,
                   segment: &ast::PathSegment,
                   span_lo: &mut BytePos,
                   span_hi: BytePos,
                   context: &RewriteContext,
                   shape: Shape)
                   -> Option<String> {
    let ident_len = segment.identifier.to_string().len();
    let shape = try_opt!(shape.shrink_left(ident_len));

    let params = if let Some(ref params) = segment.parameters {
        match **params {
            ast::PathParameters::AngleBracketed(ref data) if !data.lifetimes.is_empty() ||
                                                             !data.types.is_empty() ||
                                                             !data.bindings.is_empty() => {
                let param_list = data.lifetimes
                    .iter()
                    .map(SegmentParam::LifeTime)
                    .chain(data.types.iter().map(|x| SegmentParam::Type(&*x)))
                    .chain(data.bindings.iter().map(|x| SegmentParam::Binding(&*x)))
                    .collect::<Vec<_>>();

                let next_span_lo = param_list.last().unwrap().get_span().hi + BytePos(1);
                let list_lo = context
                    .codemap
                    .span_after(codemap::mk_sp(*span_lo, span_hi), "<");
                let separator = if path_context == PathContext::Expr {
                    "::"
                } else {
                    ""
                };

                // 1 for <
                let extra_offset = 1 + separator.len();
                // 1 for >
                // TODO bad visual indent
                let list_shape = try_opt!(try_opt!(shape.shrink_left(extra_offset)).sub_width(1))
                    .visual_indent(0);

                let items = itemize_list(context.codemap,
                                         param_list.into_iter(),
                                         ">",
                                         |param| param.get_span().lo,
                                         |param| param.get_span().hi,
                                         |seg| seg.rewrite(context, list_shape),
                                         list_lo,
                                         span_hi);
                let list_str = try_opt!(format_item_list(items, list_shape, context.config));

                // Update position of last bracket.
                *span_lo = next_span_lo;

                if context.config.spaces_within_angle_brackets() && list_str.len() > 0 {
                    format!("{}< {} >", separator, list_str)
                } else {
                    format!("{}<{}>", separator, list_str)
                }
            }
            ast::PathParameters::Parenthesized(ref data) => {
                let output = match data.output {
                    Some(ref ty) => FunctionRetTy::Ty(ty.clone()),
                    None => FunctionRetTy::Default(codemap::DUMMY_SP),
                };
                try_opt!(format_function_type(data.inputs.iter().map(|x| &**x),
                                              &output,
                                              false,
                                              data.span,
                                              context,
                                              shape))
            }
            _ => String::new(),
        }
    } else {
        String::new()
    };

    Some(format!("{}{}", segment.identifier, params))
}

fn format_function_type<'a, I>(inputs: I,
                               output: &FunctionRetTy,
                               variadic: bool,
                               span: Span,
                               context: &RewriteContext,
                               shape: Shape)
                               -> Option<String>
    where I: ExactSizeIterator,
          <I as Iterator>::Item: Deref,
          <I::Item as Deref>::Target: Rewrite + Spanned + 'a
{
    // Code for handling variadics is somewhat duplicated for items, but they
    // are different enough to need some serious refactoring to share code.
    enum ArgumentKind<T>
        where T: Deref,
              <T as Deref>::Target: Rewrite + Spanned
    {
        Regular(Box<T>),
        Variadic(BytePos),
    }

    let variadic_arg = if variadic {
        let variadic_start = context.codemap.span_before(span, "...");
        Some(ArgumentKind::Variadic(variadic_start))
    } else {
        None
    };

    // 2 for ()
    let budget = try_opt!(shape.width.checked_sub(2));
    // 1 for (
    let offset = shape.indent + 1;
    let list_lo = context.codemap.span_after(span, "(");
    let items = itemize_list(context.codemap,
                             // FIXME Would be nice to avoid this allocation,
                             // but I couldn't get the types to work out.
                             inputs
                                 .map(|i| ArgumentKind::Regular(Box::new(i)))
                                 .chain(variadic_arg),
                             ")",
                             |arg| match *arg {
                                 ArgumentKind::Regular(ref ty) => ty.span().lo,
                                 ArgumentKind::Variadic(start) => start,
                             },
                             |arg| match *arg {
                                 ArgumentKind::Regular(ref ty) => ty.span().hi,
                                 ArgumentKind::Variadic(start) => start + BytePos(3),
                             },
                             |arg| match *arg {
                                 ArgumentKind::Regular(ref ty) => {
                                     ty.rewrite(context, Shape::legacy(budget, offset))
                                 }
                                 ArgumentKind::Variadic(_) => Some("...".to_owned()),
                             },
                             list_lo,
                             span.hi);

    let list_str = try_opt!(format_fn_args(items, Shape::legacy(budget, offset), context.config));

    let output = match *output {
        FunctionRetTy::Ty(ref ty) => {
            let budget = try_opt!(shape.width.checked_sub(4));
            let type_str = try_opt!(ty.rewrite(context, Shape::legacy(budget, offset + 4)));
            format!(" -> {}", type_str)
        }
        FunctionRetTy::Default(..) => String::new(),
    };

    let infix = if !output.is_empty() && output.len() + list_str.len() > shape.width {
        format!("\n{}", (offset - 1).to_string(context.config))
    } else {
        String::new()
    };

    Some(if context.config.spaces_within_parens() {
             format!("( {} ){}{}", list_str, infix, output)
         } else {
             format!("({}){}{}", list_str, infix, output)
         })
}

fn type_bound_colon(context: &RewriteContext) -> &'static str {
    colon_spaces(context.config.space_before_bound(),
                 context.config.space_after_bound_colon())
}

impl Rewrite for ast::WherePredicate {
    fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
        // TODO: dead spans?
        let result = match *self {
            ast::WherePredicate::BoundPredicate(ast::WhereBoundPredicate {
                                                    ref bound_lifetimes,
                                                    ref bounded_ty,
                                                    ref bounds,
                                                    ..
                                                }) => {
                let type_str = try_opt!(bounded_ty.rewrite(context, shape));

                let colon = type_bound_colon(context);

                if !bound_lifetimes.is_empty() {
                    let lifetime_str: String = try_opt!(bound_lifetimes
                                                            .iter()
                                                            .map(|lt| lt.rewrite(context, shape))
                                                            .collect::<Option<Vec<_>>>())
                        .join(", ");

                    let joiner = match context.config.type_punctuation_density() {
                        TypeDensity::Compressed => "+",
                        TypeDensity::Wide => " + ",
                    };
                    // 6 = "for<> ".len()
                    let used_width = lifetime_str.len() + type_str.len() + colon.len() + 6;
                    let budget = try_opt!(shape.width.checked_sub(used_width));
                    let bounds_str: String = try_opt!(
                        bounds
                            .iter()
                            .map(|ty_bound| {
                                ty_bound.rewrite(context,
                                                 Shape::legacy(budget, shape.indent + used_width))
                            })
                            .collect::<Option<Vec<_>>>()
                    ).join(joiner);

                    if context.config.spaces_within_angle_brackets() && lifetime_str.len() > 0 {
                        format!("for< {} > {}{}{}",
                                lifetime_str,
                                type_str,
                                colon,
                                bounds_str)
                    } else {
                        format!("for<{}> {}{}{}", lifetime_str, type_str, colon, bounds_str)
                    }
                } else {
                    let joiner = match context.config.type_punctuation_density() {
                        TypeDensity::Compressed => "+",
                        TypeDensity::Wide => " + ",
                    };
                    let used_width = type_str.len() + colon.len();
                    let budget = try_opt!(shape.width.checked_sub(used_width));
                    let bounds_str: String = try_opt!(
                        bounds
                            .iter()
                            .map(|ty_bound| {
                                ty_bound.rewrite(context,
                                                 Shape::legacy(budget, shape.indent + used_width))
                            })
                            .collect::<Option<Vec<_>>>()
                    ).join(joiner);

                    format!("{}{}{}", type_str, colon, bounds_str)
                }
            }
            ast::WherePredicate::RegionPredicate(ast::WhereRegionPredicate {
                                                     ref lifetime,
                                                     ref bounds,
                                                     ..
                                                 }) => {
                try_opt!(rewrite_bounded_lifetime(lifetime, bounds.iter(), context, shape))
            }
            ast::WherePredicate::EqPredicate(ast::WhereEqPredicate {
                                                 ref lhs_ty,
                                                 ref rhs_ty,
                                                 ..
                                             }) => {
                let lhs_ty_str = try_opt!(lhs_ty.rewrite(context, shape));
                // 3 = " = ".len()
                let used_width = 3 + lhs_ty_str.len();
                let budget = try_opt!(shape.width.checked_sub(used_width));
                let rhs_ty_str = try_opt!(rhs_ty.rewrite(context,
                                                         Shape::legacy(budget,
                                                                       shape.indent + used_width)));
                format!("{} = {}", lhs_ty_str, rhs_ty_str)
            }
        };

        wrap_str(result, context.config.max_width(), shape)
    }
}

impl Rewrite for ast::LifetimeDef {
    fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
        rewrite_bounded_lifetime(&self.lifetime, self.bounds.iter(), context, shape)
    }
}

fn rewrite_bounded_lifetime<'b, I>(lt: &ast::Lifetime,
                                   bounds: I,
                                   context: &RewriteContext,
                                   shape: Shape)
                                   -> Option<String>
    where I: ExactSizeIterator<Item = &'b ast::Lifetime>
{
    let result = try_opt!(lt.rewrite(context, shape));

    if bounds.len() == 0 {
        Some(result)
    } else {
        let appendix: Vec<_> = try_opt!(bounds
                                            .into_iter()
                                            .map(|b| b.rewrite(context, shape))
                                            .collect());
        let colon = type_bound_colon(context);
        let joiner = match context.config.type_punctuation_density() {
            TypeDensity::Compressed => "+",
            TypeDensity::Wide => " + ",
        };
        let result = format!("{}{}{}", result, colon, appendix.join(joiner));
        wrap_str(result, context.config.max_width(), shape)
    }
}

impl Rewrite for ast::TyParamBound {
    fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
        match *self {
            ast::TyParamBound::TraitTyParamBound(ref tref, ast::TraitBoundModifier::None) => {
                tref.rewrite(context, shape)
            }
            ast::TyParamBound::TraitTyParamBound(ref tref, ast::TraitBoundModifier::Maybe) => {
                let budget = try_opt!(shape.width.checked_sub(1));
                Some(format!("?{}",
                             try_opt!(tref.rewrite(context,
                                                   Shape::legacy(budget, shape.indent + 1)))))
            }
            ast::TyParamBound::RegionTyParamBound(ref l) => l.rewrite(context, shape),
        }
    }
}

impl Rewrite for ast::Lifetime {
    fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
        wrap_str(pprust::lifetime_to_string(self),
                 context.config.max_width(),
                 shape)
    }
}

impl Rewrite for ast::TyParamBounds {
    fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
        let joiner = match context.config.type_punctuation_density() {
            TypeDensity::Compressed => "+",
            TypeDensity::Wide => " + ",
        };
        let strs: Vec<_> = try_opt!(self.iter().map(|b| b.rewrite(context, shape)).collect());
        wrap_str(strs.join(joiner), context.config.max_width(), shape)
    }
}

impl Rewrite for ast::TyParam {
    fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
        let mut result = String::with_capacity(128);
        // FIXME: If there are more than one attributes, this will force multiline.
        let attr_str = match (&*self.attrs).rewrite(context, shape) {
            Some(ref rw) if !rw.is_empty() => format!("{} ", rw),
            _ => String::new(),
        };
        result.push_str(&attr_str);
        result.push_str(&self.ident.to_string());
        if !self.bounds.is_empty() {
            if context.config.space_before_bound() {
                result.push_str(" ");
            }
            result.push_str(":");
            if context.config.space_after_bound_colon() {
                result.push_str(" ");
            }
            let joiner = match context.config.type_punctuation_density() {
                TypeDensity::Compressed => "+",
                TypeDensity::Wide => " + ",
            };
            let bounds: String = try_opt!(self.bounds
                                              .iter()
                                              .map(|ty_bound| ty_bound.rewrite(context, shape))
                                              .collect::<Option<Vec<_>>>())
                .join(joiner);

            result.push_str(&bounds);
        }
        if let Some(ref def) = self.default {

            let eq_str = match context.config.type_punctuation_density() {
                TypeDensity::Compressed => "=",
                TypeDensity::Wide => " = ",
            };
            result.push_str(eq_str);
            let budget = try_opt!(shape.width.checked_sub(result.len()));
            let rewrite = try_opt!(def.rewrite(context,
                                               Shape::legacy(budget, shape.indent + result.len())));
            result.push_str(&rewrite);
        }

        wrap_str(result, context.config.max_width(), shape)
    }
}

impl Rewrite for ast::PolyTraitRef {
    fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
        if !self.bound_lifetimes.is_empty() {
            let lifetime_str: String = try_opt!(self.bound_lifetimes
                                                    .iter()
                                                    .map(|lt| lt.rewrite(context, shape))
                                                    .collect::<Option<Vec<_>>>())
                .join(", ");

            // 6 is "for<> ".len()
            let extra_offset = lifetime_str.len() + 6;
            let max_path_width = try_opt!(shape.width.checked_sub(extra_offset));
            let path_str = try_opt!(self.trait_ref.rewrite(context,
                                                           Shape::legacy(max_path_width,
                                                                         shape.indent +
                                                                         extra_offset)));

            Some(if context.config.spaces_within_angle_brackets() && lifetime_str.len() > 0 {
                     format!("for< {} > {}", lifetime_str, path_str)
                 } else {
                     format!("for<{}> {}", lifetime_str, path_str)
                 })
        } else {
            self.trait_ref.rewrite(context, shape)
        }
    }
}

impl Rewrite for ast::TraitRef {
    fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
        rewrite_path(context, PathContext::Type, None, &self.path, shape)
    }
}

impl Rewrite for ast::Ty {
    fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
        match self.node {
            ast::TyKind::TraitObject(ref bounds) => bounds.rewrite(context, shape),
            ast::TyKind::Ptr(ref mt) => {
                let prefix = match mt.mutbl {
                    Mutability::Mutable => "*mut ",
                    Mutability::Immutable => "*const ",
                };

                rewrite_unary_prefix(context, prefix, &*mt.ty, shape)
            }
            ast::TyKind::Rptr(ref lifetime, ref mt) => {
                let mut_str = format_mutability(mt.mutbl);
                let mut_len = mut_str.len();
                Some(match *lifetime {
                         Some(ref lifetime) => {
                             let lt_budget = try_opt!(shape.width.checked_sub(2 + mut_len));
                             let lt_str = try_opt!(lifetime.rewrite(context,
                                                                    Shape::legacy(lt_budget,
                                                                                  shape.indent + 2 +
                                                                                  mut_len)));
                             let lt_len = lt_str.len();
                             let budget = try_opt!(shape.width.checked_sub(2 + mut_len + lt_len));
                             format!("&{} {}{}",
                                     lt_str,
                                     mut_str,
                                     try_opt!(mt.ty.rewrite(context,
                                                            Shape::legacy(budget,
                                                                          shape.indent + 2 +
                                                                          mut_len +
                                                                          lt_len))))
                         }
                         None => {
                             let budget = try_opt!(shape.width.checked_sub(1 + mut_len));
                             format!("&{}{}",
                                     mut_str,
                                     try_opt!(mt.ty.rewrite(context,
                                                            Shape::legacy(budget,
                                                                          shape.indent + 1 +
                                                                          mut_len))))
                         }
                     })
            }
            // FIXME: we drop any comments here, even though it's a silly place to put
            // comments.
            ast::TyKind::Paren(ref ty) => {
                let budget = try_opt!(shape.width.checked_sub(2));
                ty.rewrite(context, Shape::legacy(budget, shape.indent + 1))
                    .map(|ty_str| if context.config.spaces_within_parens() {
                             format!("( {} )", ty_str)
                         } else {
                             format!("({})", ty_str)
                         })
            }
            ast::TyKind::Slice(ref ty) => {
                let budget = if context.config.spaces_within_square_brackets() {
                    try_opt!(shape.width.checked_sub(4))
                } else {
                    try_opt!(shape.width.checked_sub(2))
                };
                ty.rewrite(context, Shape::legacy(budget, shape.indent + 1))
                    .map(|ty_str| if context.config.spaces_within_square_brackets() {
                             format!("[ {} ]", ty_str)
                         } else {
                             format!("[{}]", ty_str)
                         })
            }
            ast::TyKind::Tup(ref items) => {
                rewrite_tuple_type(context, items.iter().map(|x| &**x), self.span, shape)
            }
            ast::TyKind::Path(ref q_self, ref path) => {
                rewrite_path(context, PathContext::Type, q_self.as_ref(), path, shape)
            }
            ast::TyKind::Array(ref ty, ref repeats) => {
                let use_spaces = context.config.spaces_within_square_brackets();
                let lbr = if use_spaces { "[ " } else { "[" };
                let rbr = if use_spaces { " ]" } else { "]" };
                rewrite_pair(&**ty, &**repeats, lbr, "; ", rbr, context, shape)
            }
            ast::TyKind::Infer => {
                if shape.width >= 1 {
                    Some("_".to_owned())
                } else {
                    None
                }
            }
            ast::TyKind::BareFn(ref bare_fn) => rewrite_bare_fn(bare_fn, self.span, context, shape),
            ast::TyKind::Never => Some(String::from("!")),
            ast::TyKind::Mac(..) => None,
            ast::TyKind::ImplicitSelf => Some(String::from("")),
            ast::TyKind::ImplTrait(ref it) => {
                it.rewrite(context, shape)
                    .map(|it_str| format!("impl {}", it_str))
            }
            ast::TyKind::Typeof(..) => unreachable!(),
        }
    }
}

fn rewrite_bare_fn(bare_fn: &ast::BareFnTy,
                   span: Span,
                   context: &RewriteContext,
                   shape: Shape)
                   -> Option<String> {
    let mut result = String::with_capacity(128);

    if !bare_fn.lifetimes.is_empty() {
        result.push_str("for<");
        // 6 = "for<> ".len(), 4 = "for<".
        // This doesn't work out so nicely for mutliline situation with lots of
        // rightward drift. If that is a problem, we could use the list stuff.
        result.push_str(&try_opt!(
            bare_fn
                .lifetimes
                .iter()
                .map(|l| {
                    l.rewrite(context,
                              Shape::legacy(try_opt!(shape.width.checked_sub(6)), shape.indent + 4))
                })
                .collect::<Option<Vec<_>>>()
        ).join(", "));
        result.push_str("> ");
    }

    result.push_str(::utils::format_unsafety(bare_fn.unsafety));

    if bare_fn.abi != abi::Abi::Rust {
        result.push_str(&::utils::format_abi(bare_fn.abi, context.config.force_explicit_abi()));
    }

    result.push_str("fn");

    let budget = try_opt!(shape.width.checked_sub(result.len()));
    let indent = shape.indent + result.len();

    let rewrite = try_opt!(format_function_type(bare_fn.decl.inputs.iter(),
                                                &bare_fn.decl.output,
                                                bare_fn.decl.variadic,
                                                span,
                                                context,
                                                Shape::legacy(budget, indent)));

    result.push_str(&rewrite);

    Some(result)
}