rust/src/rewrite.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.

// A generic trait to abstract the rewriting of an element (of the AST).

use syntax::codemap::{CodeMap, Span};

use Indent;
use config::Config;

pub trait Rewrite {
    /// Rewrite self into offset and width.
    /// `offset` is the indentation of the first line. The next lines
    /// should begin with a least `offset` spaces (except backwards
    /// indentation). The first line should not begin with indentation.
    /// `width` is the maximum number of characters on the last line
    /// (excluding offset). The width of other lines is not limited by
    /// `width`.
    fn rewrite(&self, context: &RewriteContext, width: usize, offset: Indent) -> Option<String>;
}

pub struct RewriteContext<'a> {
    pub codemap: &'a CodeMap,
    pub config: &'a Config,

    // Indentation due to nesting of blocks.
    pub block_indent: Indent,
    // *Extra* indentation due to overflowing to the next line, e.g.,
    // let foo =
    //     bar();
    // The extra 4 spaces when formatting `bar()` is overflow_indent.
    pub overflow_indent: Indent,
}

impl<'a> RewriteContext<'a> {
    pub fn nested_context(&self) -> RewriteContext<'a> {
        RewriteContext {
            codemap: self.codemap,
            config: self.config,
            block_indent: self.block_indent.block_indent(self.config),
            overflow_indent: self.overflow_indent,
        }
    }

    pub fn overflow_context(&self, overflow: Indent) -> RewriteContext<'a> {
        RewriteContext {
            codemap: self.codemap,
            config: self.config,
            block_indent: self.block_indent,
            overflow_indent: overflow,
        }
    }

    pub fn snippet(&self, span: Span) -> String {
        self.codemap.span_to_snippet(span).unwrap()
    }
}