// 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 or the MIT license // , at your // option. This file may not be copied, modified, or distributed // except according to those terms. use std::cmp::Ordering; use std::borrow::Borrow; use std::mem::swap; use std::ops::Deref; use std::iter::ExactSizeIterator; use std::fmt::Write; use {Indent, Spanned}; use codemap::SpanUtils; use rewrite::{Rewrite, RewriteContext}; use lists::{write_list, itemize_list, ListFormatting, SeparatorTactic, ListTactic, DefinitiveListTactic, definitive_tactic, ListItem, format_item_list}; use string::{StringFormat, rewrite_string}; use utils::{extra_offset, last_line_width, wrap_str, binary_search, first_line_width, semicolon_for_stmt, trimmed_last_line_width, left_most_sub_expr}; use visitor::FmtVisitor; use config::{Config, StructLitStyle, MultilineStyle, ElseIfBraceStyle, ControlBraceStyle}; use comment::{FindUncommented, rewrite_comment, contains_comment, recover_comment_removed}; use types::rewrite_path; use items::{span_lo_for_arg, span_hi_for_arg}; use chains::rewrite_chain; use macros::rewrite_macro; use syntax::{ast, ptr}; use syntax::codemap::{CodeMap, Span, BytePos, mk_sp}; use syntax::parse::classify; impl Rewrite for ast::Expr { fn rewrite(&self, context: &RewriteContext, width: usize, offset: Indent) -> Option { format_expr(self, ExprType::SubExpression, context, width, offset) } } #[derive(PartialEq)] enum ExprType { Statement, SubExpression, } fn format_expr(expr: &ast::Expr, expr_type: ExprType, context: &RewriteContext, width: usize, offset: Indent) -> Option { let result = match expr.node { ast::ExprKind::Vec(ref expr_vec) => { rewrite_array(expr_vec.iter().map(|e| &**e), mk_sp(context.codemap.span_after(expr.span, "["), expr.span.hi), context, width, offset) } ast::ExprKind::Lit(ref l) => { match l.node { ast::LitKind::Str(_, ast::StrStyle::Cooked) => { rewrite_string_lit(context, l.span, width, offset) } _ => { wrap_str(context.snippet(expr.span), context.config.max_width, width, offset) } } } ast::ExprKind::Call(ref callee, ref args) => { let inner_span = mk_sp(callee.span.hi, expr.span.hi); rewrite_call(context, &**callee, args, inner_span, width, offset) } ast::ExprKind::Paren(ref subexpr) => rewrite_paren(context, subexpr, width, offset), ast::ExprKind::Binary(ref op, ref lhs, ref rhs) => { rewrite_binary_op(context, op, lhs, rhs, width, offset) } ast::ExprKind::Unary(ref op, ref subexpr) => { rewrite_unary_op(context, op, subexpr, width, offset) } ast::ExprKind::Struct(ref path, ref fields, ref base) => { rewrite_struct_lit(context, path, fields, base.as_ref().map(|e| &**e), expr.span, width, offset) } ast::ExprKind::Tup(ref items) => { rewrite_tuple(context, items.iter().map(|x| &**x), expr.span, width, offset) } ast::ExprKind::While(ref cond, ref block, label) => { Loop::new_while(None, cond, block, label).rewrite(context, width, offset) } ast::ExprKind::WhileLet(ref pat, ref cond, ref block, label) => { Loop::new_while(Some(pat), cond, block, label).rewrite(context, width, offset) } ast::ExprKind::ForLoop(ref pat, ref cond, ref block, label) => { Loop::new_for(pat, cond, block, label).rewrite(context, width, offset) } ast::ExprKind::Loop(ref block, label) => { Loop::new_loop(block, label).rewrite(context, width, offset) } ast::ExprKind::Block(ref block) => block.rewrite(context, width, offset), ast::ExprKind::If(ref cond, ref if_block, ref else_block) => { rewrite_if_else(context, cond, expr_type, if_block, else_block.as_ref().map(|e| &**e), expr.span, None, width, offset, true) } ast::ExprKind::IfLet(ref pat, ref cond, ref if_block, ref else_block) => { rewrite_if_else(context, cond, expr_type, if_block, else_block.as_ref().map(|e| &**e), expr.span, Some(pat), width, offset, true) } ast::ExprKind::Match(ref cond, ref arms) => { rewrite_match(context, cond, arms, width, offset, expr.span) } ast::ExprKind::Path(ref qself, ref path) => { rewrite_path(context, true, qself.as_ref(), path, width, offset) } ast::ExprKind::Assign(ref lhs, ref rhs) => { rewrite_assignment(context, lhs, rhs, None, width, offset) } ast::ExprKind::AssignOp(ref op, ref lhs, ref rhs) => { rewrite_assignment(context, lhs, rhs, Some(op), width, offset) } ast::ExprKind::Again(ref opt_ident) => { let id_str = match *opt_ident { Some(ident) => format!(" {}", ident.node), None => String::new(), }; wrap_str(format!("continue{}", id_str), context.config.max_width, width, offset) } ast::ExprKind::Break(ref opt_ident) => { let id_str = match *opt_ident { Some(ident) => format!(" {}", ident.node), None => String::new(), }; wrap_str(format!("break{}", id_str), context.config.max_width, width, offset) } ast::ExprKind::Closure(capture, ref fn_decl, ref body, _) => { rewrite_closure(capture, fn_decl, body, expr.span, context, width, offset) } ast::ExprKind::Try(..) | ast::ExprKind::Field(..) | ast::ExprKind::TupField(..) | ast::ExprKind::MethodCall(..) => rewrite_chain(expr, context, width, offset), ast::ExprKind::Mac(ref mac) => { // Failure to rewrite a marco should not imply failure to // rewrite the expression. rewrite_macro(mac, None, context, width, offset).or_else(|| { wrap_str(context.snippet(expr.span), context.config.max_width, width, offset) }) } ast::ExprKind::Ret(None) => { wrap_str("return".to_owned(), context.config.max_width, width, offset) } ast::ExprKind::Ret(Some(ref expr)) => { rewrite_unary_prefix(context, "return ", &**expr, width, offset) } ast::ExprKind::Box(ref expr) => { rewrite_unary_prefix(context, "box ", &**expr, width, offset) } ast::ExprKind::AddrOf(mutability, ref expr) => { rewrite_expr_addrof(context, mutability, expr, width, offset) } ast::ExprKind::Cast(ref expr, ref ty) => { rewrite_pair(&**expr, &**ty, "", " as ", "", context, width, offset) } ast::ExprKind::Type(ref expr, ref ty) => { rewrite_pair(&**expr, &**ty, "", ": ", "", context, width, offset) } ast::ExprKind::Index(ref expr, ref index) => { rewrite_pair(&**expr, &**index, "", "[", "]", context, width, offset) } ast::ExprKind::Repeat(ref expr, ref repeats) => { rewrite_pair(&**expr, &**repeats, "[", "; ", "]", context, width, offset) } ast::ExprKind::Range(ref lhs, ref rhs, limits) => { let delim = match limits { ast::RangeLimits::HalfOpen => "..", ast::RangeLimits::Closed => "...", }; match (lhs.as_ref().map(|x| &**x), rhs.as_ref().map(|x| &**x)) { (Some(ref lhs), Some(ref rhs)) => { rewrite_pair(&**lhs, &**rhs, "", delim, "", context, width, offset) } (None, Some(ref rhs)) => { rewrite_unary_prefix(context, delim, &**rhs, width, offset) } (Some(ref lhs), None) => { rewrite_unary_suffix(context, delim, &**lhs, width, offset) } (None, None) => wrap_str(delim.into(), context.config.max_width, width, offset), } } // We do not format these expressions yet, but they should still // satisfy our width restrictions. ast::ExprKind::InPlace(..) | ast::ExprKind::InlineAsm(..) => { wrap_str(context.snippet(expr.span), context.config.max_width, width, offset) } }; result.and_then(|res| recover_comment_removed(res, expr.span, context, width, offset)) } pub fn rewrite_pair(lhs: &LHS, rhs: &RHS, prefix: &str, infix: &str, suffix: &str, context: &RewriteContext, width: usize, offset: Indent) -> Option where LHS: Rewrite, RHS: Rewrite { let max_width = try_opt!(width.checked_sub(prefix.len() + infix.len() + suffix.len())); binary_search(1, max_width, |lhs_budget| { let lhs_offset = offset + prefix.len(); let lhs_str = match lhs.rewrite(context, lhs_budget, lhs_offset) { Some(result) => result, None => return Err(Ordering::Greater), }; let last_line_width = last_line_width(&lhs_str); let rhs_budget = match max_width.checked_sub(last_line_width) { Some(b) => b, None => return Err(Ordering::Less), }; let rhs_indent = offset + last_line_width + prefix.len() + infix.len(); let rhs_str = match rhs.rewrite(context, rhs_budget, rhs_indent) { Some(result) => result, None => return Err(Ordering::Less), }; Ok(format!("{}{}{}{}{}", prefix, lhs_str, infix, rhs_str, suffix)) }) } pub fn rewrite_array<'a, I>(expr_iter: I, span: Span, context: &RewriteContext, width: usize, offset: Indent) -> Option where I: Iterator { // 2 for brackets; let offset = offset + 1; let inner_context = &RewriteContext { block_indent: offset, ..*context }; let max_item_width = try_opt!(width.checked_sub(2)); let items = itemize_list(context.codemap, expr_iter, "]", |item| item.span.lo, |item| item.span.hi, // 1 = [ |item| item.rewrite(&inner_context, max_item_width, offset), span.lo, span.hi) .collect::>(); let has_long_item = try_opt!(items.iter() .map(|li| li.item.as_ref().map(|s| s.len() > 10)) .fold(Some(false), |acc, x| acc.and_then(|y| x.map(|x| x || y)))); let tactic = if has_long_item || items.iter().any(ListItem::is_multiline) { definitive_tactic(&items, ListTactic::HorizontalVertical, max_item_width) } else { DefinitiveListTactic::Mixed }; let fmt = ListFormatting { tactic: tactic, separator: ",", trailing_separator: SeparatorTactic::Never, indent: offset, width: max_item_width, ends_with_newline: false, config: context.config, }; let list_str = try_opt!(write_list(&items, &fmt)); Some(format!("[{}]", list_str)) } // This functions is pretty messy because of the rules around closures and blocks: // * the body of a closure is represented by an ast::Block, but that does not // imply there are `{}` (unless the block is empty) (see rust issue #27872), // * if there is a return type, then there must be braces, // * given a closure with braces, whether that is parsed to give an inner block // or not depends on if there is a return type and if there are statements // in that block, // * if the first expression in the body ends with a block (i.e., is a // statement without needing a semi-colon), then adding or removing braces // can change whether it is treated as an expression or statement. fn rewrite_closure(capture: ast::CaptureBy, fn_decl: &ast::FnDecl, body: &ast::Block, span: Span, context: &RewriteContext, width: usize, offset: Indent) -> Option { let mover = if capture == ast::CaptureBy::Value { "move " } else { "" }; let offset = offset + mover.len(); // 4 = "|| {".len(), which is overconservative when the closure consists of // a single expression. let budget = try_opt!(width.checked_sub(4 + mover.len())); // 1 = | let argument_offset = offset + 1; let ret_str = try_opt!(fn_decl.output.rewrite(context, budget, argument_offset)); let force_block = !ret_str.is_empty(); // 1 = space between arguments and return type. let horizontal_budget = budget.checked_sub(ret_str.len() + 1).unwrap_or(0); let arg_items = itemize_list(context.codemap, fn_decl.inputs.iter(), "|", |arg| span_lo_for_arg(arg), |arg| span_hi_for_arg(arg), |arg| arg.rewrite(context, budget, argument_offset), context.codemap.span_after(span, "|"), body.span.lo); let item_vec = arg_items.collect::>(); let tactic = definitive_tactic(&item_vec, ListTactic::HorizontalVertical, horizontal_budget); let budget = match tactic { DefinitiveListTactic::Horizontal => horizontal_budget, _ => budget, }; let fmt = ListFormatting { tactic: tactic, separator: ",", trailing_separator: SeparatorTactic::Never, indent: argument_offset, width: budget, ends_with_newline: false, config: context.config, }; let list_str = try_opt!(write_list(&item_vec, &fmt)); let mut prefix = format!("{}|{}|", mover, list_str); if !ret_str.is_empty() { if prefix.contains('\n') { prefix.push('\n'); prefix.push_str(&argument_offset.to_string(context.config)); } else { prefix.push(' '); } prefix.push_str(&ret_str); } if body.expr.is_none() && body.stmts.is_empty() { return Some(format!("{} {{}}", prefix)); } // 1 = space between `|...|` and body. let extra_offset = extra_offset(&prefix, offset) + 1; let budget = try_opt!(width.checked_sub(extra_offset)); // This is where we figure out whether to use braces or not. let mut had_braces = true; let mut inner_block = body; // If there is an inner block and we can ignore it, do so. if body.stmts.is_empty() { if let ast::ExprKind::Block(ref inner) = inner_block.expr.as_ref().unwrap().node { inner_block = inner; } else if !force_block { had_braces = false; } } let try_single_line = is_simple_block(inner_block, context.codemap) && inner_block.rules == ast::BlockCheckMode::Default; if try_single_line && !force_block { let must_preserve_braces = !classify::expr_requires_semi_to_be_stmt(left_most_sub_expr(inner_block.expr .as_ref() .unwrap())); if !(must_preserve_braces && had_braces) && (must_preserve_braces || !prefix.contains('\n')) { // If we got here, then we can try to format without braces. let inner_expr = inner_block.expr.as_ref().unwrap(); let mut rewrite = inner_expr.rewrite(context, budget, offset + extra_offset); if must_preserve_braces { // If we are here, then failure to rewrite is unacceptable. if rewrite.is_none() { return None; } } else { // Checks if rewrite succeeded and fits on a single line. rewrite = and_one_line(rewrite); } if let Some(rewrite) = rewrite { return Some(format!("{} {}", prefix, rewrite)); } } } // If we fell through the above block, then we need braces, but we might // still prefer a one-liner (we might also have fallen through because of // lack of space). if try_single_line && !prefix.contains('\n') { let inner_expr = inner_block.expr.as_ref().unwrap(); // 4 = braces and spaces. let mut rewrite = inner_expr.rewrite(context, try_opt!(budget.checked_sub(4)), offset + extra_offset); // Checks if rewrite succeeded and fits on a single line. rewrite = and_one_line(rewrite); if let Some(rewrite) = rewrite { return Some(format!("{} {{ {} }}", prefix, rewrite)); } } // We couldn't format the closure body as a single line expression; fall // back to block formatting. let body_rewrite = try_opt!(inner_block.rewrite(&context, budget, Indent::empty())); let block_threshold = context.config.closure_block_indent_threshold; if block_threshold < 0 || body_rewrite.matches('\n').count() <= block_threshold as usize { return Some(format!("{} {}", prefix, body_rewrite)); } // The body of the closure is big enough to be block indented, that means we // must re-format. let mut context = context.clone(); context.block_indent.alignment = 0; let body_rewrite = try_opt!(inner_block.rewrite(&context, budget, Indent::empty())); Some(format!("{} {}", prefix, body_rewrite)) } fn and_one_line(x: Option) -> Option { x.and_then(|x| if x.contains('\n') { None } else { Some(x) }) } fn nop_block_collapse(block_str: Option, budget: usize) -> Option { block_str.map(|block_str| { if block_str.starts_with("{") && budget >= 2 && (block_str[1..].find(|c: char| !c.is_whitespace()).unwrap() == block_str.len() - 2) { "{}".to_owned() } else { block_str.to_owned() } }) } impl Rewrite for ast::Block { fn rewrite(&self, context: &RewriteContext, width: usize, offset: Indent) -> Option { // width is used only for the single line case: either the empty block `{}`, // or an unsafe expression `unsafe { e }`. let user_str = context.snippet(self.span); if user_str == "{}" && width >= 2 { return Some(user_str); } let mut visitor = FmtVisitor::from_codemap(context.parse_session, context.config); visitor.block_indent = context.block_indent; let prefix = match self.rules { ast::BlockCheckMode::Unsafe(..) => { let snippet = context.snippet(self.span); let open_pos = try_opt!(snippet.find_uncommented("{")); visitor.last_pos = self.span.lo + BytePos(open_pos as u32); // Extract comment between unsafe and block start. let trimmed = &snippet[6..open_pos].trim(); let prefix = if !trimmed.is_empty() { // 9 = "unsafe {".len(), 7 = "unsafe ".len() let budget = try_opt!(width.checked_sub(9)); format!("unsafe {} ", try_opt!(rewrite_comment(trimmed, true, budget, offset + 7, context.config))) } else { "unsafe ".to_owned() }; if is_simple_block(self, context.codemap) && prefix.len() < width { let body = self.expr .as_ref() .unwrap() .rewrite(context, width - prefix.len(), offset); if let Some(ref expr_str) = body { let result = format!("{}{{ {} }}", prefix, expr_str); if result.len() <= width && !result.contains('\n') { return Some(result); } } } prefix } ast::BlockCheckMode::Default => { visitor.last_pos = self.span.lo; String::new() } }; visitor.visit_block(self); Some(format!("{}{}", prefix, visitor.buffer)) } } impl Rewrite for ast::Stmt { fn rewrite(&self, context: &RewriteContext, _width: usize, offset: Indent) -> Option { let result = match self.node { ast::StmtKind::Decl(ref decl, _) => { if let ast::DeclKind::Local(ref local) = decl.node { local.rewrite(context, context.config.max_width, offset) } else { None } } ast::StmtKind::Expr(ref ex, _) | ast::StmtKind::Semi(ref ex, _) => { let suffix = if semicolon_for_stmt(self) { ";" } else { "" }; format_expr(ex, ExprType::Statement, context, context.config.max_width - offset.width() - suffix.len(), offset) .map(|s| s + suffix) } ast::StmtKind::Mac(..) => None, }; result.and_then(|res| recover_comment_removed(res, self.span, context, _width, offset)) } } // Abstraction over for, while and loop expressions struct Loop<'a> { cond: Option<&'a ast::Expr>, block: &'a ast::Block, label: Option, pat: Option<&'a ast::Pat>, keyword: &'a str, matcher: &'a str, connector: &'a str, } impl<'a> Loop<'a> { fn new_loop(block: &'a ast::Block, label: Option) -> Loop<'a> { Loop { cond: None, block: block, label: label, pat: None, keyword: "loop", matcher: "", connector: "", } } fn new_while(pat: Option<&'a ast::Pat>, cond: &'a ast::Expr, block: &'a ast::Block, label: Option) -> Loop<'a> { Loop { cond: Some(cond), block: block, label: label, pat: pat, keyword: "while ", matcher: match pat { Some(..) => "let ", None => "", }, connector: " =", } } fn new_for(pat: &'a ast::Pat, cond: &'a ast::Expr, block: &'a ast::Block, label: Option) -> Loop<'a> { Loop { cond: Some(cond), block: block, label: label, pat: Some(pat), keyword: "for ", matcher: "", connector: " in", } } } impl<'a> Rewrite for Loop<'a> { fn rewrite(&self, context: &RewriteContext, width: usize, offset: Indent) -> Option { let label_string = rewrite_label(self.label); // 2 = " {".len() let inner_width = try_opt!(width.checked_sub(self.keyword.len() + 2 + label_string.len())); let inner_offset = offset + self.keyword.len() + label_string.len(); let pat_expr_string = match self.cond { Some(cond) => { try_opt!(rewrite_pat_expr(context, self.pat, cond, self.matcher, self.connector, inner_width, inner_offset)) } None => String::new(), }; let alt_block_sep = String::from("\n") + &context.block_indent.to_string(context.config); let block_sep = match context.config.control_brace_style { ControlBraceStyle::AlwaysNextLine => alt_block_sep.as_str(), ControlBraceStyle::AlwaysSameLine => " ", }; // This is used only for the empty block case: `{}` let block_width = try_opt!(width.checked_sub(label_string.len() + self.keyword.len() + extra_offset(&pat_expr_string, inner_offset) + 1)); // FIXME: this drops any comment between "loop" and the block. self.block .rewrite(context, block_width, offset) .map(|result| { format!("{}{}{}{}{}", label_string, self.keyword, pat_expr_string, block_sep, result) }) } } fn rewrite_label(label: Option) -> String { match label { Some(ident) => format!("{}: ", ident.node), None => "".to_owned(), } } fn extract_comment(span: Span, context: &RewriteContext, offset: Indent, width: usize) -> Option { let comment_str = context.snippet(span); if contains_comment(&comment_str) { let comment = try_opt!(rewrite_comment(comment_str.trim(), false, width, offset, context.config)); Some(format!("\n{indent}{}\n{indent}", comment, indent = offset.to_string(context.config))) } else { None } } // Rewrites if-else blocks. If let Some(_) = pat, the expression is // treated as an if-let-else expression. fn rewrite_if_else(context: &RewriteContext, cond: &ast::Expr, expr_type: ExprType, if_block: &ast::Block, else_block_opt: Option<&ast::Expr>, span: Span, pat: Option<&ast::Pat>, width: usize, offset: Indent, allow_single_line: bool) -> Option { let (budget, indent) = if !allow_single_line { // We are part of an if-elseif-else chain. Our constraints are tightened. // 7 = "} else" .len() (try_opt!(width.checked_sub(7)), offset + 7) } else { (width, offset) }; // 3 = "if ", 2 = " {" let pat_penalty = match context.config.else_if_brace_style { ElseIfBraceStyle::AlwaysNextLine => 3, _ => 3 + 2, }; let pat_expr_string = try_opt!(rewrite_pat_expr(context, pat, cond, "let ", " =", try_opt!(budget.checked_sub(pat_penalty)), indent + 3)); // Try to format if-else on single line. if expr_type == ExprType::SubExpression && allow_single_line && context.config.single_line_if_else_max_width > 0 { let trial = single_line_if_else(context, &pat_expr_string, if_block, else_block_opt, width); if trial.is_some() && trial.as_ref().unwrap().len() <= context.config.single_line_if_else_max_width { return trial; } } let if_block_string = try_opt!(if_block.rewrite(context, width, offset)); let between_if_cond = mk_sp(context.codemap.span_after(span, "if"), pat.map_or(cond.span.lo, |_| context.codemap.span_before(span, "let"))); let between_if_cond_comment = extract_comment(between_if_cond, &context, offset, width); let after_cond_comment = extract_comment(mk_sp(cond.span.hi, if_block.span.lo), context, offset, width); let alt_block_sep = String::from("\n") + &context.block_indent.to_string(context.config); let after_sep = match context.config.else_if_brace_style { ElseIfBraceStyle::AlwaysNextLine => alt_block_sep.as_str(), _ => " ", }; let mut result = format!("if{}{}{}{}", between_if_cond_comment.as_ref().map_or(" ", |str| &**str), pat_expr_string, after_cond_comment.as_ref().map_or(after_sep, |str| &**str), if_block_string); if let Some(else_block) = else_block_opt { let mut last_in_chain = false; let rewrite = match else_block.node { // If the else expression is another if-else expression, prevent it // from being formatted on a single line. // Note how we're passing the original width and offset, as the // cost of "else" should not cascade. ast::ExprKind::IfLet(ref pat, ref cond, ref if_block, ref next_else_block) => { rewrite_if_else(context, cond, expr_type, if_block, next_else_block.as_ref().map(|e| &**e), mk_sp(else_block.span.lo, span.hi), Some(pat), width, offset, false) } ast::ExprKind::If(ref cond, ref if_block, ref next_else_block) => { rewrite_if_else(context, cond, expr_type, if_block, next_else_block.as_ref().map(|e| &**e), mk_sp(else_block.span.lo, span.hi), None, width, offset, false) } _ => { last_in_chain = true; else_block.rewrite(context, width, offset) } }; let between_if_else_block = mk_sp(if_block.span.hi, context.codemap.span_before(mk_sp(if_block.span.hi, else_block.span.lo), "else")); let between_if_else_block_comment = extract_comment(between_if_else_block, &context, offset, width); let after_else = mk_sp(context.codemap .span_after(mk_sp(if_block.span.hi, else_block.span.lo), "else"), else_block.span.lo); let after_else_comment = extract_comment(after_else, &context, offset, width); let between_sep = match context.config.else_if_brace_style { ElseIfBraceStyle::AlwaysNextLine | ElseIfBraceStyle::ClosingNextLine => alt_block_sep.as_str(), ElseIfBraceStyle::AlwaysSameLine => " ", }; let after_sep = match context.config.else_if_brace_style { ElseIfBraceStyle::AlwaysNextLine if last_in_chain => alt_block_sep.as_str(), _ => " ", }; try_opt!(write!(&mut result, "{}else{}", between_if_else_block_comment.as_ref() .map_or(between_sep, |str| &**str), after_else_comment.as_ref().map_or(after_sep, |str| &**str)) .ok()); result.push_str(&&try_opt!(rewrite)); } Some(result) } fn single_line_if_else(context: &RewriteContext, pat_expr_str: &str, if_node: &ast::Block, else_block_opt: Option<&ast::Expr>, width: usize) -> Option { let else_block = try_opt!(else_block_opt); let fixed_cost = "if { } else { }".len(); if let ast::ExprKind::Block(ref else_node) = else_block.node { if !is_simple_block(if_node, context.codemap) || !is_simple_block(else_node, context.codemap) || pat_expr_str.contains('\n') { return None; } let new_width = try_opt!(width.checked_sub(pat_expr_str.len() + fixed_cost)); let if_expr = if_node.expr.as_ref().unwrap(); let if_str = try_opt!(if_expr.rewrite(context, new_width, Indent::empty())); let new_width = try_opt!(new_width.checked_sub(if_str.len())); let else_expr = else_node.expr.as_ref().unwrap(); let else_str = try_opt!(else_expr.rewrite(context, new_width, Indent::empty())); // FIXME: this check shouldn't be necessary. Rewrites should either fail // or wrap to a newline when the object does not fit the width. let fits_line = fixed_cost + pat_expr_str.len() + if_str.len() + else_str.len() <= width; if fits_line && !if_str.contains('\n') && !else_str.contains('\n') { return Some(format!("if {} {{ {} }} else {{ {} }}", pat_expr_str, if_str, else_str)); } } None } fn block_contains_comment(block: &ast::Block, codemap: &CodeMap) -> bool { let snippet = codemap.span_to_snippet(block.span).unwrap(); contains_comment(&snippet) } // Checks that a block contains no statements, an expression and no comments. // FIXME: incorrectly returns false when comment is contained completely within // the expression. pub fn is_simple_block(block: &ast::Block, codemap: &CodeMap) -> bool { block.stmts.is_empty() && block.expr.is_some() && !block_contains_comment(block, codemap) } /// Checks whether a block contains at most one statement or expression, and no comments. pub fn is_simple_block_stmt(block: &ast::Block, codemap: &CodeMap) -> bool { (block.stmts.is_empty() || (block.stmts.len() == 1 && block.expr.is_none())) && !block_contains_comment(block, codemap) } /// Checks whether a block contains no statements, expressions, or comments. pub fn is_empty_block(block: &ast::Block, codemap: &CodeMap) -> bool { block.stmts.is_empty() && block.expr.is_none() && !block_contains_comment(block, codemap) } fn is_unsafe_block(block: &ast::Block) -> bool { if let ast::BlockCheckMode::Unsafe(..) = block.rules { true } else { false } } // inter-match-arm-comment-rules: // - all comments following a match arm before the start of the next arm // are about the second arm fn rewrite_match_arm_comment(context: &RewriteContext, missed_str: &str, width: usize, arm_indent: Indent, arm_indent_str: &str) -> Option { // The leading "," is not part of the arm-comment let missed_str = match missed_str.find_uncommented(",") { Some(n) => &missed_str[n + 1..], None => &missed_str[..], }; let mut result = String::new(); // any text not preceeded by a newline is pushed unmodified to the block let first_brk = missed_str.find(|c: char| c == '\n').unwrap_or(0); result.push_str(&missed_str[..first_brk]); let missed_str = &missed_str[first_brk..]; // If missed_str had one newline, it starts with it let first = missed_str.find(|c: char| !c.is_whitespace()).unwrap_or(missed_str.len()); if missed_str[..first].chars().filter(|c| c == &'\n').count() >= 2 { // Excessive vertical whitespace before comment should be preserved // TODO handle vertical whitespace better result.push('\n'); } let missed_str = missed_str[first..].trim(); if !missed_str.is_empty() { let comment = try_opt!(rewrite_comment(&missed_str, false, width, arm_indent, context.config)); result.push('\n'); result.push_str(arm_indent_str); result.push_str(&comment); } Some(result) } fn rewrite_match(context: &RewriteContext, cond: &ast::Expr, arms: &[ast::Arm], width: usize, offset: Indent, span: Span) -> Option { if arms.is_empty() { return None; } // `match `cond` {` let cond_budget = try_opt!(width.checked_sub(8)); let cond_str = try_opt!(cond.rewrite(context, cond_budget, offset + 6)); let alt_block_sep = String::from("\n") + &context.block_indent.to_string(context.config); let block_sep = match context.config.control_brace_style { ControlBraceStyle::AlwaysSameLine => " ", ControlBraceStyle::AlwaysNextLine => alt_block_sep.as_str(), }; let mut result = format!("match {}{}{{", cond_str, block_sep); let nested_context = context.nested_context(); let arm_indent = nested_context.block_indent; let arm_indent_str = arm_indent.to_string(context.config); let open_brace_pos = context.codemap .span_after(mk_sp(cond.span.hi, arm_start_pos(&arms[0])), "{"); for (i, arm) in arms.iter().enumerate() { // Make sure we get the stuff between arms. let missed_str = if i == 0 { context.snippet(mk_sp(open_brace_pos, arm_start_pos(arm))) } else { context.snippet(mk_sp(arm_end_pos(&arms[i - 1]), arm_start_pos(arm))) }; let comment = try_opt!(rewrite_match_arm_comment(context, &missed_str, width, arm_indent, &arm_indent_str)); result.push_str(&comment); result.push('\n'); result.push_str(&arm_indent_str); let arm_str = arm.rewrite(&nested_context, context.config.max_width - arm_indent.width(), arm_indent); if let Some(ref arm_str) = arm_str { result.push_str(arm_str); } else { // We couldn't format the arm, just reproduce the source. let snippet = context.snippet(mk_sp(arm_start_pos(arm), arm_end_pos(arm))); result.push_str(&snippet); result.push_str(arm_comma(&context.config, &arm, &arm.body)); } } // BytePos(1) = closing match brace. let last_span = mk_sp(arm_end_pos(&arms[arms.len() - 1]), span.hi - BytePos(1)); let last_comment = context.snippet(last_span); let comment = try_opt!(rewrite_match_arm_comment(context, &last_comment, width, arm_indent, &arm_indent_str)); result.push_str(&comment); result.push('\n'); result.push_str(&context.block_indent.to_string(context.config)); result.push('}'); Some(result) } fn arm_start_pos(arm: &ast::Arm) -> BytePos { let &ast::Arm { ref attrs, ref pats, .. } = arm; if !attrs.is_empty() { return attrs[0].span.lo; } pats[0].span.lo } fn arm_end_pos(arm: &ast::Arm) -> BytePos { arm.body.span.hi } fn arm_comma(config: &Config, arm: &ast::Arm, body: &ast::Expr) -> &'static str { if !config.match_wildcard_trailing_comma { if arm.pats.len() == 1 && arm.pats[0].node == ast::PatKind::Wild && arm.guard.is_none() { return ""; } } if config.match_block_trailing_comma { "," } else if let ast::ExprKind::Block(ref block) = body.node { if let ast::BlockCheckMode::Default = block.rules { "" } else { "," } } else { "," } } // Match arms. impl Rewrite for ast::Arm { fn rewrite(&self, context: &RewriteContext, width: usize, offset: Indent) -> Option { let &ast::Arm { ref attrs, ref pats, ref guard, ref body } = self; // FIXME this is all a bit grotty, would be nice to abstract out the // treatment of attributes. let attr_str = if !attrs.is_empty() { // We only use this visitor for the attributes, should we use it for // more? let mut attr_visitor = FmtVisitor::from_codemap(context.parse_session, context.config); attr_visitor.block_indent = context.block_indent; attr_visitor.last_pos = attrs[0].span.lo; if attr_visitor.visit_attrs(attrs) { // Attributes included a skip instruction. return None; } attr_visitor.format_missing(pats[0].span.lo); attr_visitor.buffer.to_string() } else { String::new() }; // Patterns // 5 = ` => {` let pat_budget = try_opt!(width.checked_sub(5)); let pat_strs = try_opt!(pats.iter() .map(|p| p.rewrite(context, pat_budget, offset)) .collect::>>()); let all_simple = pat_strs.iter().all(|p| pat_is_simple(&p)); let items: Vec<_> = pat_strs.into_iter().map(ListItem::from_str).collect(); let fmt = ListFormatting { tactic: if all_simple { DefinitiveListTactic::Mixed } else { DefinitiveListTactic::Vertical }, separator: " |", trailing_separator: SeparatorTactic::Never, indent: offset, width: pat_budget, ends_with_newline: false, config: context.config, }; let pats_str = try_opt!(write_list(items, &fmt)); let budget = if pats_str.contains('\n') { context.config.max_width - offset.width() } else { width }; let guard_str = try_opt!(rewrite_guard(context, guard, budget, offset, trimmed_last_line_width(&pats_str))); let pats_str = format!("{}{}", pats_str, guard_str); // Where the next text can start. let mut line_start = last_line_width(&pats_str); if !pats_str.contains('\n') { line_start += offset.width(); } let body = match **body { ast::Expr { node: ast::ExprKind::Block(ref block), .. } if !is_unsafe_block(block) && is_simple_block(block, context.codemap) && context.config.wrap_match_arms => block.expr.as_ref().map(|e| &**e).unwrap(), ref x => x, }; let comma = arm_comma(&context.config, self, body); let alt_block_sep = String::from("\n") + &context.block_indent.to_string(context.config); // Let's try and get the arm body on the same line as the condition. // 4 = ` => `.len() if context.config.max_width > line_start + comma.len() + 4 { let budget = context.config.max_width - line_start - comma.len() - 4; let offset = Indent::new(offset.block_indent, line_start + 4 - offset.block_indent); let rewrite = nop_block_collapse(body.rewrite(context, budget, offset), budget); let is_block = if let ast::ExprKind::Block(..) = body.node { true } else { false }; let block_sep = match context.config.control_brace_style { ControlBraceStyle::AlwaysNextLine if is_block => alt_block_sep.as_str(), _ => " ", }; match rewrite { Some(ref body_str) if !body_str.contains('\n') || !context.config.wrap_match_arms || is_block => { return Some(format!("{}{} =>{}{}{}", attr_str.trim_left(), pats_str, block_sep, body_str, comma)); } _ => {} } } // FIXME: we're doing a second rewrite of the expr; This may not be // necessary. let body_budget = try_opt!(width.checked_sub(context.config.tab_spaces)); let indent = context.block_indent.block_indent(context.config); let inner_context = &RewriteContext { block_indent: indent, ..*context }; let next_line_body = try_opt!(nop_block_collapse(body.rewrite(inner_context, body_budget, indent), body_budget)); let indent_str = offset.block_indent(context.config).to_string(context.config); let (body_prefix, body_suffix) = if context.config.wrap_match_arms { if context.config.match_block_trailing_comma { (" {", "},") } else { (" {", "}") } } else { ("", "") }; let block_sep = match context.config.control_brace_style { ControlBraceStyle::AlwaysNextLine => alt_block_sep, ControlBraceStyle::AlwaysSameLine => String::from(body_prefix) + "\n", }; Some(format!("{}{} =>{}{}{}\n{}{}", attr_str.trim_left(), pats_str, block_sep, indent_str, next_line_body, offset.to_string(context.config), body_suffix)) } } // A pattern is simple if it is very short or it is short-ish and just a path. // E.g. `Foo::Bar` is simple, but `Foo(..)` is not. fn pat_is_simple(pat_str: &str) -> bool { pat_str.len() <= 16 || (pat_str.len() <= 24 && pat_str.chars().all(|c| c.is_alphabetic() || c == ':')) } // The `if ...` guard on a match arm. fn rewrite_guard(context: &RewriteContext, guard: &Option>, width: usize, offset: Indent, // The amount of space used up on this line for the pattern in // the arm (excludes offset). pattern_width: usize) -> Option { if let Some(ref guard) = *guard { // First try to fit the guard string on the same line as the pattern. // 4 = ` if `, 5 = ` => {` let overhead = pattern_width + 4 + 5; if overhead < width { let cond_str = guard.rewrite(context, width - overhead, offset + pattern_width + 4); if let Some(cond_str) = cond_str { return Some(format!(" if {}", cond_str)); } } // Not enough space to put the guard after the pattern, try a newline. let overhead = offset.block_indent(context.config).width() + 4 + 5; if overhead < width { let cond_str = guard.rewrite(context, width - overhead, // 3 == `if ` offset.block_indent(context.config) + 3); if let Some(cond_str) = cond_str { return Some(format!("\n{}if {}", offset.block_indent(context.config).to_string(context.config), cond_str)); } } None } else { Some(String::new()) } } fn rewrite_pat_expr(context: &RewriteContext, pat: Option<&ast::Pat>, expr: &ast::Expr, matcher: &str, // Connecting piece between pattern and expression, // *without* trailing space. connector: &str, width: usize, offset: Indent) -> Option { let pat_offset = offset + matcher.len(); let mut result = match pat { Some(pat) => { let pat_budget = try_opt!(width.checked_sub(connector.len() + matcher.len())); let pat_string = try_opt!(pat.rewrite(context, pat_budget, pat_offset)); format!("{}{}{}", matcher, pat_string, connector) } None => String::new(), }; // Consider only the last line of the pat string. let extra_offset = extra_offset(&result, offset); // The expression may (partionally) fit on the current line. if width > extra_offset + 1 { let spacer = if pat.is_some() { " " } else { "" }; let expr_rewrite = expr.rewrite(context, try_opt!(width.checked_sub(extra_offset + spacer.len())), offset + extra_offset + spacer.len()); if let Some(expr_string) = expr_rewrite { result.push_str(spacer); result.push_str(&expr_string); return Some(result); } } // The expression won't fit on the current line, jump to next. result.push('\n'); result.push_str(&pat_offset.to_string(context.config)); let expr_rewrite = expr.rewrite(context, try_opt!(context.config.max_width.checked_sub(pat_offset.width())), pat_offset); result.push_str(&&try_opt!(expr_rewrite)); Some(result) } fn rewrite_string_lit(context: &RewriteContext, span: Span, width: usize, offset: Indent) -> Option { let string_lit = context.snippet(span); if !context.config.format_strings && !context.config.force_format_strings { return Some(string_lit); } if !context.config.force_format_strings && !string_requires_rewrite(context, span, &string_lit, width, offset) { return Some(string_lit); } let fmt = StringFormat { opener: "\"", closer: "\"", line_start: " ", line_end: "\\", width: width, offset: offset, trim_end: false, config: context.config, }; // Remove the quote characters. let str_lit = &string_lit[1..string_lit.len() - 1]; rewrite_string(str_lit, &fmt) } fn string_requires_rewrite(context: &RewriteContext, span: Span, string: &str, width: usize, offset: Indent) -> bool { if context.codemap.lookup_char_pos(span.lo).col.0 != offset.width() { return true; } for (i, line) in string.lines().enumerate() { if i == 0 { if line.len() > width { return true; } } else { if line.len() > width + offset.width() { return true; } } } false } pub fn rewrite_call(context: &RewriteContext, callee: &R, args: &[ptr::P], span: Span, width: usize, offset: Indent) -> Option where R: Rewrite { let closure = |callee_max_width| { rewrite_call_inner(context, callee, callee_max_width, args, span, width, offset) }; // 2 is for parens let max_width = try_opt!(width.checked_sub(2)); binary_search(1, max_width, closure) } fn rewrite_call_inner(context: &RewriteContext, callee: &R, max_callee_width: usize, args: &[ptr::P], span: Span, width: usize, offset: Indent) -> Result where R: Rewrite { let callee = callee.borrow(); // FIXME using byte lens instead of char lens (and probably all over the // place too) let callee_str = match callee.rewrite(context, max_callee_width, offset) { Some(string) => { if !string.contains('\n') && string.len() > max_callee_width { panic!("{:?} {}", string, max_callee_width); } else { string } } None => return Err(Ordering::Greater), }; let span_lo = context.codemap.span_after(span, "("); let span = mk_sp(span_lo, span.hi); let extra_offset = extra_offset(&callee_str, offset); // 2 is for parens. let remaining_width = match width.checked_sub(extra_offset + 2) { Some(str) => str, None => return Err(Ordering::Greater), }; let offset = offset + extra_offset + 1; let arg_count = args.len(); let block_indent = if arg_count == 1 { context.block_indent } else { offset }; let inner_context = &RewriteContext { block_indent: block_indent, ..*context }; let items = itemize_list(context.codemap, args.iter(), ")", |item| item.span.lo, |item| item.span.hi, |item| item.rewrite(&inner_context, remaining_width, offset), span.lo, span.hi); let mut item_vec: Vec<_> = items.collect(); // Try letting the last argument overflow to the next line with block // indentation. If its first line fits on one line with the other arguments, // we format the function arguments horizontally. let overflow_last = match args.last().map(|x| &x.node) { Some(&ast::ExprKind::Closure(..)) | Some(&ast::ExprKind::Block(..)) if arg_count > 1 => true, _ => false, } && context.config.chains_overflow_last; let mut orig_last = None; let mut placeholder = None; // Replace the last item with its first line to see if it fits with // first arguments. if overflow_last { let inner_context = &RewriteContext { block_indent: context.block_indent, ..*context }; let rewrite = args.last().unwrap().rewrite(&inner_context, remaining_width, offset); if let Some(rewrite) = rewrite { let rewrite_first_line = Some(rewrite[..first_line_width(&rewrite)].to_owned()); placeholder = Some(rewrite); swap(&mut item_vec[arg_count - 1].item, &mut orig_last); item_vec[arg_count - 1].item = rewrite_first_line; } } let tactic = definitive_tactic(&item_vec, ListTactic::LimitedHorizontalVertical(context.config .fn_call_width), remaining_width); // Replace the stub with the full overflowing last argument if the rewrite // succeeded and its first line fits with the other arguments. match (overflow_last, tactic, placeholder) { (true, DefinitiveListTactic::Horizontal, placeholder @ Some(..)) => { item_vec[arg_count - 1].item = placeholder; } (true, _, _) => { item_vec[arg_count - 1].item = orig_last; } (false, _, _) => {} } let fmt = ListFormatting { tactic: tactic, separator: ",", trailing_separator: SeparatorTactic::Never, indent: offset, width: width, ends_with_newline: false, config: context.config, }; let list_str = match write_list(&item_vec, &fmt) { Some(str) => str, None => return Err(Ordering::Less), }; Ok(format!("{}({})", callee_str, list_str)) } fn rewrite_paren(context: &RewriteContext, subexpr: &ast::Expr, width: usize, offset: Indent) -> Option { debug!("rewrite_paren, width: {}, offset: {:?}", width, offset); // 1 is for opening paren, 2 is for opening+closing, we want to keep the closing // paren on the same line as the subexpr. let subexpr_str = subexpr.rewrite(context, try_opt!(width.checked_sub(2)), offset + 1); debug!("rewrite_paren, subexpr_str: `{:?}`", subexpr_str); subexpr_str.map(|s| format!("({})", s)) } fn rewrite_struct_lit<'a>(context: &RewriteContext, path: &ast::Path, fields: &'a [ast::Field], base: Option<&'a ast::Expr>, span: Span, width: usize, offset: Indent) -> Option { debug!("rewrite_struct_lit: width {}, offset {:?}", width, offset); enum StructLitField<'a> { Regular(&'a ast::Field), Base(&'a ast::Expr), } // 2 = " {".len() let path_budget = try_opt!(width.checked_sub(2)); let path_str = try_opt!(rewrite_path(context, true, None, path, path_budget, offset)); // Foo { a: Foo } - indent is +3, width is -5. let h_budget = width.checked_sub(path_str.len() + 5).unwrap_or(0); // The 1 taken from the v_budget is for the comma. let (indent, v_budget) = match context.config.struct_lit_style { StructLitStyle::Visual => (offset + path_str.len() + 3, h_budget), StructLitStyle::Block => { // If we are all on one line, then we'll ignore the indent, and we // have a smaller budget. let indent = context.block_indent.block_indent(context.config); let v_budget = context.config.max_width.checked_sub(indent.width()).unwrap_or(0); (indent, v_budget) } }; let field_iter = fields.into_iter() .map(StructLitField::Regular) .chain(base.into_iter().map(StructLitField::Base)); let inner_context = &RewriteContext { block_indent: indent, ..*context }; let items = itemize_list(context.codemap, field_iter, "}", |item| { match *item { StructLitField::Regular(ref field) => field.span.lo, StructLitField::Base(ref expr) => { let last_field_hi = fields.last().map_or(span.lo, |field| field.span.hi); let snippet = context.snippet(mk_sp(last_field_hi, expr.span.lo)); let pos = snippet.find_uncommented("..").unwrap(); last_field_hi + BytePos(pos as u32) } } }, |item| { match *item { StructLitField::Regular(ref field) => field.span.hi, StructLitField::Base(ref expr) => expr.span.hi, } }, |item| { match *item { StructLitField::Regular(ref field) => { rewrite_field(inner_context, &field, v_budget.checked_sub(1).unwrap_or(0), indent) } StructLitField::Base(ref expr) => { // 2 = .. expr.rewrite(inner_context, try_opt!(v_budget.checked_sub(2)), indent + 2) .map(|s| format!("..{}", s)) } } }, context.codemap.span_after(span, "{"), span.hi); let item_vec = items.collect::>(); let tactic = { let mut prelim_tactic = match (context.config.struct_lit_style, fields.len()) { (StructLitStyle::Visual, 1) => ListTactic::HorizontalVertical, _ => context.config.struct_lit_multiline_style.to_list_tactic(), }; if prelim_tactic == ListTactic::HorizontalVertical && fields.len() > 1 { prelim_tactic = ListTactic::LimitedHorizontalVertical(context.config.struct_lit_width); } definitive_tactic(&item_vec, prelim_tactic, h_budget) }; let budget = match tactic { DefinitiveListTactic::Horizontal => h_budget, _ => v_budget, }; let ends_with_newline = context.config.struct_lit_style != StructLitStyle::Visual && tactic == DefinitiveListTactic::Vertical; let fmt = ListFormatting { tactic: tactic, separator: ",", trailing_separator: if base.is_some() { SeparatorTactic::Never } else { context.config.struct_lit_trailing_comma }, indent: indent, width: budget, ends_with_newline: ends_with_newline, config: context.config, }; let fields_str = try_opt!(write_list(&item_vec, &fmt)); if fields_str.is_empty() { return Some(format!("{} {{}}", path_str)); } let format_on_newline = || { let inner_indent = context.block_indent .block_indent(context.config) .to_string(context.config); let outer_indent = context.block_indent.to_string(context.config); Some(format!("{} {{\n{}{}\n{}}}", path_str, inner_indent, fields_str, outer_indent)) }; match (context.config.struct_lit_style, context.config.struct_lit_multiline_style) { (StructLitStyle::Block, _) if fields_str.contains('\n') || fields_str.len() > h_budget => { format_on_newline() } (StructLitStyle::Block, MultilineStyle::ForceMulti) => format_on_newline(), _ => Some(format!("{} {{ {} }}", path_str, fields_str)), } // FIXME if context.config.struct_lit_style == Visual, but we run out // of space, we should fall back to BlockIndent. } fn rewrite_field(context: &RewriteContext, field: &ast::Field, width: usize, offset: Indent) -> Option { let name = &field.ident.node.to_string(); let overhead = name.len() + 2; let expr = field.expr.rewrite(context, try_opt!(width.checked_sub(overhead)), offset + overhead); match expr { Some(e) => Some(format!("{}: {}", name, e)), None => { let expr_offset = offset.block_indent(&context.config); let expr = field.expr.rewrite(context, try_opt!(context.config .max_width .checked_sub(expr_offset.width())), expr_offset); expr.map(|s| format!("{}:\n{}{}", name, expr_offset.to_string(&context.config), s)) } } } pub fn rewrite_tuple<'a, I>(context: &RewriteContext, mut items: I, span: Span, width: usize, offset: Indent) -> Option where I: ExactSizeIterator, ::Item: Deref, ::Target: Rewrite + Spanned + 'a { let indent = offset + 1; // In case of length 1, need a trailing comma if items.len() == 1 { // 3 = "(" + ",)" let budget = try_opt!(width.checked_sub(3)); return items.next().unwrap().rewrite(context, budget, indent).map(|s| format!("({},)", s)); } let list_lo = context.codemap.span_after(span, "("); let items = itemize_list(context.codemap, items, ")", |item| item.span().lo, |item| item.span().hi, |item| { let inner_width = try_opt!(context.config .max_width .checked_sub(indent.width() + 1)); item.rewrite(context, inner_width, indent) }, list_lo, span.hi - BytePos(1)); let budget = try_opt!(width.checked_sub(2)); let list_str = try_opt!(format_item_list(items, budget, indent, context.config)); Some(format!("({})", list_str)) } fn rewrite_binary_op(context: &RewriteContext, op: &ast::BinOp, lhs: &ast::Expr, rhs: &ast::Expr, width: usize, offset: Indent) -> Option { // FIXME: format comments between operands and operator let operator_str = context.snippet(op.span); // Get "full width" rhs and see if it fits on the current line. This // usually works fairly well since it tends to place operands of // operations with high precendence close together. let rhs_result = try_opt!(rhs.rewrite(context, width, offset)); // Second condition is needed in case of line break not caused by a // shortage of space, but by end-of-line comments, for example. // Note that this is non-conservative, but its just to see if it's even // worth trying to put everything on one line. if rhs_result.len() + 2 + operator_str.len() < width && !rhs_result.contains('\n') { // 1 = space between lhs expr and operator if let Some(mut result) = lhs.rewrite(context, width - 1 - operator_str.len(), offset) { result.push(' '); result.push_str(&operator_str); result.push(' '); let remaining_width = width.checked_sub(last_line_width(&result)).unwrap_or(0); if rhs_result.len() <= remaining_width { result.push_str(&rhs_result); return Some(result); } if let Some(rhs_result) = rhs.rewrite(context, remaining_width, offset + result.len()) { if rhs_result.len() <= remaining_width { result.push_str(&rhs_result); return Some(result); } } } } // We have to use multiple lines. // Re-evaluate the lhs because we have more space now: let budget = try_opt!(context.config .max_width .checked_sub(offset.width() + 1 + operator_str.len())); Some(format!("{} {}\n{}{}", try_opt!(lhs.rewrite(context, budget, offset)), operator_str, offset.to_string(context.config), rhs_result)) } pub fn rewrite_unary_prefix(context: &RewriteContext, prefix: &str, rewrite: &R, width: usize, offset: Indent) -> Option { rewrite.rewrite(context, try_opt!(width.checked_sub(prefix.len())), offset + prefix.len()) .map(|r| format!("{}{}", prefix, r)) } // FIXME: this is probably not correct for multi-line Rewrites. we should // subtract suffix.len() from the last line budget, not the first! pub fn rewrite_unary_suffix(context: &RewriteContext, suffix: &str, rewrite: &R, width: usize, offset: Indent) -> Option { rewrite.rewrite(context, try_opt!(width.checked_sub(suffix.len())), offset) .map(|mut r| { r.push_str(suffix); r }) } fn rewrite_unary_op(context: &RewriteContext, op: &ast::UnOp, expr: &ast::Expr, width: usize, offset: Indent) -> Option { // For some reason, an UnOp is not spanned like BinOp! let operator_str = match *op { ast::UnOp::Deref => "*", ast::UnOp::Not => "!", ast::UnOp::Neg => "-", }; rewrite_unary_prefix(context, operator_str, expr, width, offset) } fn rewrite_assignment(context: &RewriteContext, lhs: &ast::Expr, rhs: &ast::Expr, op: Option<&ast::BinOp>, width: usize, offset: Indent) -> Option { let operator_str = match op { Some(op) => context.snippet(op.span), None => "=".to_owned(), }; // 1 = space between lhs and operator. let max_width = try_opt!(width.checked_sub(operator_str.len() + 1)); let lhs_str = format!("{} {}", try_opt!(lhs.rewrite(context, max_width, offset)), operator_str); rewrite_assign_rhs(&context, lhs_str, rhs, width, offset) } // The left hand side must contain everything up to, and including, the // assignment operator. pub fn rewrite_assign_rhs>(context: &RewriteContext, lhs: S, ex: &ast::Expr, width: usize, offset: Indent) -> Option { let mut result = lhs.into(); let last_line_width = last_line_width(&result) - if result.contains('\n') { offset.width() } else { 0 }; // 1 = space between operator and rhs. let max_width = try_opt!(width.checked_sub(last_line_width + 1)); let rhs = ex.rewrite(&context, max_width, offset + last_line_width + 1); fn count_line_breaks(src: &str) -> usize { src.chars().filter(|&x| x == '\n').count() } match rhs { Some(ref new_str) if count_line_breaks(new_str) < 2 => { result.push(' '); result.push_str(new_str); } _ => { // Expression did not fit on the same line as the identifier or is // at least three lines big. Try splitting the line and see // if that works better. let new_offset = offset.block_indent(context.config); let max_width = try_opt!((width + offset.width()).checked_sub(new_offset.width())); let inner_context = context.nested_context(); let new_rhs = ex.rewrite(&inner_context, max_width, new_offset); // FIXME: DRY! match (rhs, new_rhs) { (Some(ref orig_rhs), Some(ref replacement_rhs)) if count_line_breaks(orig_rhs) > count_line_breaks(replacement_rhs) + 1 => { result.push_str(&format!("\n{}", new_offset.to_string(context.config))); result.push_str(replacement_rhs); } (None, Some(ref final_rhs)) => { result.push_str(&format!("\n{}", new_offset.to_string(context.config))); result.push_str(final_rhs); } (None, None) => return None, (Some(ref orig_rhs), _) => { result.push(' '); result.push_str(orig_rhs); } } } } Some(result) } fn rewrite_expr_addrof(context: &RewriteContext, mutability: ast::Mutability, expr: &ast::Expr, width: usize, offset: Indent) -> Option { let operator_str = match mutability { ast::Mutability::Immutable => "&", ast::Mutability::Mutable => "&mut ", }; rewrite_unary_prefix(context, operator_str, expr, width, offset) }