--- /dev/null
+//! Formatting of chained expressions, i.e., expressions that are chained by
+//! dots: struct and enum field access, method calls, and try shorthand (`?`).
+//!
+//! Instead of walking these subexpressions one-by-one, as is our usual strategy
+//! for expression formatting, we collect maximal sequences of these expressions
+//! and handle them simultaneously.
+//!
+//! Whenever possible, the entire chain is put on a single line. If that fails,
+//! we put each subexpression on a separate, much like the (default) function
+//! argument function argument strategy.
+//!
+//! Depends on config options: `chain_indent` is the indent to use for
+//! blocks in the parent/root/base of the chain (and the rest of the chain's
+//! alignment).
+//! E.g., `let foo = { aaaa; bbb; ccc }.bar.baz();`, we would layout for the
+//! following values of `chain_indent`:
+//! Block:
+//!
+//! ```text
+//! let foo = {
+//! aaaa;
+//! bbb;
+//! ccc
+//! }.bar
+//! .baz();
+//! ```
+//!
+//! Visual:
+//!
+//! ```text
+//! let foo = {
+//! aaaa;
+//! bbb;
+//! ccc
+//! }
+//! .bar
+//! .baz();
+//! ```
+//!
+//! If the first item in the chain is a block expression, we align the dots with
+//! the braces.
+//! Block:
+//!
+//! ```text
+//! let a = foo.bar
+//! .baz()
+//! .qux
+//! ```
+//!
+//! Visual:
+//!
+//! ```text
+//! let a = foo.bar
+//! .baz()
+//! .qux
+//! ```
+
+use std::borrow::Cow;
+use std::cmp::min;
+
+use rustc_ast::{ast, ptr};
+use rustc_span::{symbol, BytePos, Span};
+
+use crate::comment::{rewrite_comment, CharClasses, FullCodeCharKind, RichChar};
+use crate::config::{IndentStyle, Version};
+use crate::expr::rewrite_call;
+use crate::lists::extract_pre_comment;
+use crate::macros::convert_try_mac;
+use crate::rewrite::{Rewrite, RewriteContext};
+use crate::shape::Shape;
+use crate::source_map::SpanUtils;
+use crate::utils::{
+ self, first_line_width, last_line_extendable, last_line_width, mk_sp, rewrite_ident,
+ trimmed_last_line_width, wrap_str,
+};
+
+pub(crate) fn rewrite_chain(
+ expr: &ast::Expr,
+ context: &RewriteContext<'_>,
+ shape: Shape,
+) -> Option<String> {
+ let chain = Chain::from_ast(expr, context);
+ debug!("rewrite_chain {:?} {:?}", chain, shape);
+
+ // If this is just an expression with some `?`s, then format it trivially and
+ // return early.
+ if chain.children.is_empty() {
+ return chain.parent.rewrite(context, shape);
+ }
+
+ chain.rewrite(context, shape)
+}
+
+#[derive(Debug)]
+enum CommentPosition {
+ Back,
+ Top,
+}
+
+// An expression plus trailing `?`s to be formatted together.
+#[derive(Debug)]
+struct ChainItem {
+ kind: ChainItemKind,
+ tries: usize,
+ span: Span,
+}
+
+// FIXME: we can't use a reference here because to convert `try!` to `?` we
+// synthesise the AST node. However, I think we could use `Cow` and that
+// would remove a lot of cloning.
+#[derive(Debug)]
+enum ChainItemKind {
+ Parent(ast::Expr),
+ MethodCall(
+ ast::PathSegment,
+ Vec<ast::GenericArg>,
+ Vec<ptr::P<ast::Expr>>,
+ ),
+ StructField(symbol::Ident),
+ TupleField(symbol::Ident, bool),
+ Await,
+ Comment(String, CommentPosition),
+}
+
+impl ChainItemKind {
+ fn is_block_like(&self, context: &RewriteContext<'_>, reps: &str) -> bool {
+ match self {
+ ChainItemKind::Parent(ref expr) => utils::is_block_expr(context, expr, reps),
+ ChainItemKind::MethodCall(..)
+ | ChainItemKind::StructField(..)
+ | ChainItemKind::TupleField(..)
+ | ChainItemKind::Await
+ | ChainItemKind::Comment(..) => false,
+ }
+ }
+
+ fn is_tup_field_access(expr: &ast::Expr) -> bool {
+ match expr.kind {
+ ast::ExprKind::Field(_, ref field) => {
+ field.name.to_string().chars().all(|c| c.is_digit(10))
+ }
+ _ => false,
+ }
+ }
+
+ fn from_ast(context: &RewriteContext<'_>, expr: &ast::Expr) -> (ChainItemKind, Span) {
+ let (kind, span) = match expr.kind {
+ ast::ExprKind::MethodCall(ref segment, ref expressions, _) => {
+ let types = if let Some(ref generic_args) = segment.args {
+ if let ast::GenericArgs::AngleBracketed(ref data) = **generic_args {
+ data.args
+ .iter()
+ .filter_map(|x| match x {
+ ast::AngleBracketedArg::Arg(ref generic_arg) => {
+ Some(generic_arg.clone())
+ }
+ _ => None,
+ })
+ .collect::<Vec<_>>()
+ } else {
+ vec![]
+ }
+ } else {
+ vec![]
+ };
+ let span = mk_sp(expressions[0].span.hi(), expr.span.hi());
+ let kind = ChainItemKind::MethodCall(segment.clone(), types, expressions.clone());
+ (kind, span)
+ }
+ ast::ExprKind::Field(ref nested, field) => {
+ let kind = if Self::is_tup_field_access(expr) {
+ ChainItemKind::TupleField(field, Self::is_tup_field_access(nested))
+ } else {
+ ChainItemKind::StructField(field)
+ };
+ let span = mk_sp(nested.span.hi(), field.span.hi());
+ (kind, span)
+ }
+ ast::ExprKind::Await(ref nested) => {
+ let span = mk_sp(nested.span.hi(), expr.span.hi());
+ (ChainItemKind::Await, span)
+ }
+ _ => return (ChainItemKind::Parent(expr.clone()), expr.span),
+ };
+
+ // Remove comments from the span.
+ let lo = context.snippet_provider.span_before(span, ".");
+ (kind, mk_sp(lo, span.hi()))
+ }
+}
+
+impl Rewrite for ChainItem {
+ fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+ let shape = shape.sub_width(self.tries)?;
+ let rewrite = match self.kind {
+ ChainItemKind::Parent(ref expr) => expr.rewrite(context, shape)?,
+ ChainItemKind::MethodCall(ref segment, ref types, ref exprs) => {
+ Self::rewrite_method_call(segment.ident, types, exprs, self.span, context, shape)?
+ }
+ ChainItemKind::StructField(ident) => format!(".{}", rewrite_ident(context, ident)),
+ ChainItemKind::TupleField(ident, nested) => format!(
+ "{}.{}",
+ if nested && context.config.version() == Version::One {
+ " "
+ } else {
+ ""
+ },
+ rewrite_ident(context, ident)
+ ),
+ ChainItemKind::Await => ".await".to_owned(),
+ ChainItemKind::Comment(ref comment, _) => {
+ rewrite_comment(comment, false, shape, context.config)?
+ }
+ };
+ Some(format!("{}{}", rewrite, "?".repeat(self.tries)))
+ }
+}
+
+impl ChainItem {
+ fn new(context: &RewriteContext<'_>, expr: &ast::Expr, tries: usize) -> ChainItem {
+ let (kind, span) = ChainItemKind::from_ast(context, expr);
+ ChainItem { kind, tries, span }
+ }
+
+ fn comment(span: Span, comment: String, pos: CommentPosition) -> ChainItem {
+ ChainItem {
+ kind: ChainItemKind::Comment(comment, pos),
+ tries: 0,
+ span,
+ }
+ }
+
+ fn is_comment(&self) -> bool {
+ match self.kind {
+ ChainItemKind::Comment(..) => true,
+ _ => false,
+ }
+ }
+
+ fn rewrite_method_call(
+ method_name: symbol::Ident,
+ types: &[ast::GenericArg],
+ args: &[ptr::P<ast::Expr>],
+ span: Span,
+ context: &RewriteContext<'_>,
+ shape: Shape,
+ ) -> Option<String> {
+ let type_str = if types.is_empty() {
+ String::new()
+ } else {
+ let type_list = types
+ .iter()
+ .map(|ty| ty.rewrite(context, shape))
+ .collect::<Option<Vec<_>>>()?;
+
+ format!("::<{}>", type_list.join(", "))
+ };
+ let callee_str = format!(".{}{}", rewrite_ident(context, method_name), type_str);
+ rewrite_call(context, &callee_str, &args[1..], span, shape)
+ }
+}
+
+#[derive(Debug)]
+struct Chain {
+ parent: ChainItem,
+ children: Vec<ChainItem>,
+}
+
+impl Chain {
+ fn from_ast(expr: &ast::Expr, context: &RewriteContext<'_>) -> Chain {
+ let subexpr_list = Self::make_subexpr_list(expr, context);
+
+ // Un-parse the expression tree into ChainItems
+ let mut rev_children = vec![];
+ let mut sub_tries = 0;
+ for subexpr in &subexpr_list {
+ match subexpr.kind {
+ ast::ExprKind::Try(_) => sub_tries += 1,
+ _ => {
+ rev_children.push(ChainItem::new(context, subexpr, sub_tries));
+ sub_tries = 0;
+ }
+ }
+ }
+
+ fn is_tries(s: &str) -> bool {
+ s.chars().all(|c| c == '?')
+ }
+
+ fn is_post_comment(s: &str) -> bool {
+ let comment_start_index = s.chars().position(|c| c == '/');
+ if comment_start_index.is_none() {
+ return false;
+ }
+
+ let newline_index = s.chars().position(|c| c == '\n');
+ if newline_index.is_none() {
+ return true;
+ }
+
+ comment_start_index.unwrap() < newline_index.unwrap()
+ }
+
+ fn handle_post_comment(
+ post_comment_span: Span,
+ post_comment_snippet: &str,
+ prev_span_end: &mut BytePos,
+ children: &mut Vec<ChainItem>,
+ ) {
+ let white_spaces: &[_] = &[' ', '\t'];
+ if post_comment_snippet
+ .trim_matches(white_spaces)
+ .starts_with('\n')
+ {
+ // No post comment.
+ return;
+ }
+ let trimmed_snippet = trim_tries(post_comment_snippet);
+ if is_post_comment(&trimmed_snippet) {
+ children.push(ChainItem::comment(
+ post_comment_span,
+ trimmed_snippet.trim().to_owned(),
+ CommentPosition::Back,
+ ));
+ *prev_span_end = post_comment_span.hi();
+ }
+ }
+
+ let parent = rev_children.pop().unwrap();
+ let mut children = vec![];
+ let mut prev_span_end = parent.span.hi();
+ let mut iter = rev_children.into_iter().rev().peekable();
+ if let Some(first_chain_item) = iter.peek() {
+ let comment_span = mk_sp(prev_span_end, first_chain_item.span.lo());
+ let comment_snippet = context.snippet(comment_span);
+ if !is_tries(comment_snippet.trim()) {
+ handle_post_comment(
+ comment_span,
+ comment_snippet,
+ &mut prev_span_end,
+ &mut children,
+ );
+ }
+ }
+ while let Some(chain_item) = iter.next() {
+ let comment_snippet = context.snippet(chain_item.span);
+ // FIXME: Figure out the way to get a correct span when converting `try!` to `?`.
+ let handle_comment =
+ !(context.config.use_try_shorthand() || is_tries(comment_snippet.trim()));
+
+ // Pre-comment
+ if handle_comment {
+ let pre_comment_span = mk_sp(prev_span_end, chain_item.span.lo());
+ let pre_comment_snippet = trim_tries(context.snippet(pre_comment_span));
+ let (pre_comment, _) = extract_pre_comment(&pre_comment_snippet);
+ match pre_comment {
+ Some(ref comment) if !comment.is_empty() => {
+ children.push(ChainItem::comment(
+ pre_comment_span,
+ comment.to_owned(),
+ CommentPosition::Top,
+ ));
+ }
+ _ => (),
+ }
+ }
+
+ prev_span_end = chain_item.span.hi();
+ children.push(chain_item);
+
+ // Post-comment
+ if !handle_comment || iter.peek().is_none() {
+ continue;
+ }
+
+ let next_lo = iter.peek().unwrap().span.lo();
+ let post_comment_span = mk_sp(prev_span_end, next_lo);
+ let post_comment_snippet = context.snippet(post_comment_span);
+ handle_post_comment(
+ post_comment_span,
+ post_comment_snippet,
+ &mut prev_span_end,
+ &mut children,
+ );
+ }
+
+ Chain { parent, children }
+ }
+
+ // Returns a Vec of the prefixes of the chain.
+ // E.g., for input `a.b.c` we return [`a.b.c`, `a.b`, 'a']
+ fn make_subexpr_list(expr: &ast::Expr, context: &RewriteContext<'_>) -> Vec<ast::Expr> {
+ let mut subexpr_list = vec![expr.clone()];
+
+ while let Some(subexpr) = Self::pop_expr_chain(subexpr_list.last().unwrap(), context) {
+ subexpr_list.push(subexpr.clone());
+ }
+
+ subexpr_list
+ }
+
+ // Returns the expression's subexpression, if it exists. When the subexpr
+ // is a try! macro, we'll convert it to shorthand when the option is set.
+ fn pop_expr_chain(expr: &ast::Expr, context: &RewriteContext<'_>) -> Option<ast::Expr> {
+ match expr.kind {
+ ast::ExprKind::MethodCall(_, ref expressions, _) => {
+ Some(Self::convert_try(&expressions[0], context))
+ }
+ ast::ExprKind::Field(ref subexpr, _)
+ | ast::ExprKind::Try(ref subexpr)
+ | ast::ExprKind::Await(ref subexpr) => Some(Self::convert_try(subexpr, context)),
+ _ => None,
+ }
+ }
+
+ fn convert_try(expr: &ast::Expr, context: &RewriteContext<'_>) -> ast::Expr {
+ match expr.kind {
+ ast::ExprKind::MacCall(ref mac) if context.config.use_try_shorthand() => {
+ if let Some(subexpr) = convert_try_mac(mac, context) {
+ subexpr
+ } else {
+ expr.clone()
+ }
+ }
+ _ => expr.clone(),
+ }
+ }
+}
+
+impl Rewrite for Chain {
+ fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+ debug!("rewrite chain {:?} {:?}", self, shape);
+
+ let mut formatter = match context.config.indent_style() {
+ IndentStyle::Block => {
+ Box::new(ChainFormatterBlock::new(self)) as Box<dyn ChainFormatter>
+ }
+ IndentStyle::Visual => {
+ Box::new(ChainFormatterVisual::new(self)) as Box<dyn ChainFormatter>
+ }
+ };
+
+ formatter.format_root(&self.parent, context, shape)?;
+ if let Some(result) = formatter.pure_root() {
+ return wrap_str(result, context.config.max_width(), shape);
+ }
+
+ // Decide how to layout the rest of the chain.
+ let child_shape = formatter.child_shape(context, shape)?;
+
+ formatter.format_children(context, child_shape)?;
+ formatter.format_last_child(context, shape, child_shape)?;
+
+ let result = formatter.join_rewrites(context, child_shape)?;
+ wrap_str(result, context.config.max_width(), shape)
+ }
+}
+
+// There are a few types for formatting chains. This is because there is a lot
+// in common between formatting with block vs visual indent, but they are
+// different enough that branching on the indent all over the place gets ugly.
+// Anything that can format a chain is a ChainFormatter.
+trait ChainFormatter {
+ // Parent is the first item in the chain, e.g., `foo` in `foo.bar.baz()`.
+ // Root is the parent plus any other chain items placed on the first line to
+ // avoid an orphan. E.g.,
+ // ```text
+ // foo.bar
+ // .baz()
+ // ```
+ // If `bar` were not part of the root, then foo would be orphaned and 'float'.
+ fn format_root(
+ &mut self,
+ parent: &ChainItem,
+ context: &RewriteContext<'_>,
+ shape: Shape,
+ ) -> Option<()>;
+ fn child_shape(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<Shape>;
+ fn format_children(&mut self, context: &RewriteContext<'_>, child_shape: Shape) -> Option<()>;
+ fn format_last_child(
+ &mut self,
+ context: &RewriteContext<'_>,
+ shape: Shape,
+ child_shape: Shape,
+ ) -> Option<()>;
+ fn join_rewrites(&self, context: &RewriteContext<'_>, child_shape: Shape) -> Option<String>;
+ // Returns `Some` if the chain is only a root, None otherwise.
+ fn pure_root(&mut self) -> Option<String>;
+}
+
+// Data and behaviour that is shared by both chain formatters. The concrete
+// formatters can delegate much behaviour to `ChainFormatterShared`.
+struct ChainFormatterShared<'a> {
+ // The current working set of child items.
+ children: &'a [ChainItem],
+ // The current rewrites of items (includes trailing `?`s, but not any way to
+ // connect the rewrites together).
+ rewrites: Vec<String>,
+ // Whether the chain can fit on one line.
+ fits_single_line: bool,
+ // The number of children in the chain. This is not equal to `self.children.len()`
+ // because `self.children` will change size as we process the chain.
+ child_count: usize,
+}
+
+impl<'a> ChainFormatterShared<'a> {
+ fn new(chain: &'a Chain) -> ChainFormatterShared<'a> {
+ ChainFormatterShared {
+ children: &chain.children,
+ rewrites: Vec::with_capacity(chain.children.len() + 1),
+ fits_single_line: false,
+ child_count: chain.children.len(),
+ }
+ }
+
+ fn pure_root(&mut self) -> Option<String> {
+ if self.children.is_empty() {
+ assert_eq!(self.rewrites.len(), 1);
+ Some(self.rewrites.pop().unwrap())
+ } else {
+ None
+ }
+ }
+
+ // Rewrite the last child. The last child of a chain requires special treatment. We need to
+ // know whether 'overflowing' the last child make a better formatting:
+ //
+ // A chain with overflowing the last child:
+ // ```text
+ // parent.child1.child2.last_child(
+ // a,
+ // b,
+ // c,
+ // )
+ // ```
+ //
+ // A chain without overflowing the last child (in vertical layout):
+ // ```text
+ // parent
+ // .child1
+ // .child2
+ // .last_child(a, b, c)
+ // ```
+ //
+ // In particular, overflowing is effective when the last child is a method with a multi-lined
+ // block-like argument (e.g., closure):
+ // ```text
+ // parent.child1.child2.last_child(|a, b, c| {
+ // let x = foo(a, b, c);
+ // let y = bar(a, b, c);
+ //
+ // // ...
+ //
+ // result
+ // })
+ // ```
+ fn format_last_child(
+ &mut self,
+ may_extend: bool,
+ context: &RewriteContext<'_>,
+ shape: Shape,
+ child_shape: Shape,
+ ) -> Option<()> {
+ let last = self.children.last()?;
+ let extendable = may_extend && last_line_extendable(&self.rewrites[0]);
+ let prev_last_line_width = last_line_width(&self.rewrites[0]);
+
+ // Total of all items excluding the last.
+ let almost_total = if extendable {
+ prev_last_line_width
+ } else {
+ self.rewrites
+ .iter()
+ .map(|rw| utils::unicode_str_width(&rw))
+ .sum()
+ } + last.tries;
+ let one_line_budget = if self.child_count == 1 {
+ shape.width
+ } else {
+ min(shape.width, context.config.width_heuristics().chain_width)
+ }
+ .saturating_sub(almost_total);
+
+ let all_in_one_line = !self.children.iter().any(ChainItem::is_comment)
+ && self.rewrites.iter().all(|s| !s.contains('\n'))
+ && one_line_budget > 0;
+ let last_shape = if all_in_one_line {
+ shape.sub_width(last.tries)?
+ } else if extendable {
+ child_shape.sub_width(last.tries)?
+ } else {
+ child_shape.sub_width(shape.rhs_overhead(context.config) + last.tries)?
+ };
+
+ let mut last_subexpr_str = None;
+ if all_in_one_line || extendable {
+ // First we try to 'overflow' the last child and see if it looks better than using
+ // vertical layout.
+ let one_line_shape = if context.use_block_indent() {
+ last_shape.offset_left(almost_total)
+ } else {
+ last_shape
+ .visual_indent(almost_total)
+ .sub_width(almost_total)
+ };
+
+ if let Some(one_line_shape) = one_line_shape {
+ if let Some(rw) = last.rewrite(context, one_line_shape) {
+ // We allow overflowing here only if both of the following conditions match:
+ // 1. The entire chain fits in a single line except the last child.
+ // 2. `last_child_str.lines().count() >= 5`.
+ let line_count = rw.lines().count();
+ let could_fit_single_line = first_line_width(&rw) <= one_line_budget;
+ if could_fit_single_line && line_count >= 5 {
+ last_subexpr_str = Some(rw);
+ self.fits_single_line = all_in_one_line;
+ } else {
+ // We could not know whether overflowing is better than using vertical
+ // layout, just by looking at the overflowed rewrite. Now we rewrite the
+ // last child on its own line, and compare two rewrites to choose which is
+ // better.
+ let last_shape = child_shape
+ .sub_width(shape.rhs_overhead(context.config) + last.tries)?;
+ match last.rewrite(context, last_shape) {
+ Some(ref new_rw) if !could_fit_single_line => {
+ last_subexpr_str = Some(new_rw.clone());
+ }
+ Some(ref new_rw) if new_rw.lines().count() >= line_count => {
+ last_subexpr_str = Some(rw);
+ self.fits_single_line = could_fit_single_line && all_in_one_line;
+ }
+ new_rw @ Some(..) => {
+ last_subexpr_str = new_rw;
+ }
+ _ => {
+ last_subexpr_str = Some(rw);
+ self.fits_single_line = could_fit_single_line && all_in_one_line;
+ }
+ }
+ }
+ }
+ }
+ }
+
+ let last_shape = if context.use_block_indent() {
+ last_shape
+ } else {
+ child_shape.sub_width(shape.rhs_overhead(context.config) + last.tries)?
+ };
+
+ last_subexpr_str = last_subexpr_str.or_else(|| last.rewrite(context, last_shape));
+ self.rewrites.push(last_subexpr_str?);
+ Some(())
+ }
+
+ fn join_rewrites(&self, context: &RewriteContext<'_>, child_shape: Shape) -> Option<String> {
+ let connector = if self.fits_single_line {
+ // Yay, we can put everything on one line.
+ Cow::from("")
+ } else {
+ // Use new lines.
+ if context.force_one_line_chain.get() {
+ return None;
+ }
+ child_shape.to_string_with_newline(context.config)
+ };
+
+ let mut rewrite_iter = self.rewrites.iter();
+ let mut result = rewrite_iter.next().unwrap().clone();
+ let children_iter = self.children.iter();
+ let iter = rewrite_iter.zip(children_iter);
+
+ for (rewrite, chain_item) in iter {
+ match chain_item.kind {
+ ChainItemKind::Comment(_, CommentPosition::Back) => result.push(' '),
+ ChainItemKind::Comment(_, CommentPosition::Top) => result.push_str(&connector),
+ _ => result.push_str(&connector),
+ }
+ result.push_str(&rewrite);
+ }
+
+ Some(result)
+ }
+}
+
+// Formats a chain using block indent.
+struct ChainFormatterBlock<'a> {
+ shared: ChainFormatterShared<'a>,
+ root_ends_with_block: bool,
+}
+
+impl<'a> ChainFormatterBlock<'a> {
+ fn new(chain: &'a Chain) -> ChainFormatterBlock<'a> {
+ ChainFormatterBlock {
+ shared: ChainFormatterShared::new(chain),
+ root_ends_with_block: false,
+ }
+ }
+}
+
+impl<'a> ChainFormatter for ChainFormatterBlock<'a> {
+ fn format_root(
+ &mut self,
+ parent: &ChainItem,
+ context: &RewriteContext<'_>,
+ shape: Shape,
+ ) -> Option<()> {
+ let mut root_rewrite: String = parent.rewrite(context, shape)?;
+
+ let mut root_ends_with_block = parent.kind.is_block_like(context, &root_rewrite);
+ let tab_width = context.config.tab_spaces().saturating_sub(shape.offset);
+
+ while root_rewrite.len() <= tab_width && !root_rewrite.contains('\n') {
+ let item = &self.shared.children[0];
+ if let ChainItemKind::Comment(..) = item.kind {
+ break;
+ }
+ let shape = shape.offset_left(root_rewrite.len())?;
+ match &item.rewrite(context, shape) {
+ Some(rewrite) => root_rewrite.push_str(rewrite),
+ None => break,
+ }
+
+ root_ends_with_block = last_line_extendable(&root_rewrite);
+
+ self.shared.children = &self.shared.children[1..];
+ if self.shared.children.is_empty() {
+ break;
+ }
+ }
+ self.shared.rewrites.push(root_rewrite);
+ self.root_ends_with_block = root_ends_with_block;
+ Some(())
+ }
+
+ fn child_shape(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<Shape> {
+ Some(
+ if self.root_ends_with_block {
+ shape.block_indent(0)
+ } else {
+ shape.block_indent(context.config.tab_spaces())
+ }
+ .with_max_width(context.config),
+ )
+ }
+
+ fn format_children(&mut self, context: &RewriteContext<'_>, child_shape: Shape) -> Option<()> {
+ for item in &self.shared.children[..self.shared.children.len() - 1] {
+ let rewrite = item.rewrite(context, child_shape)?;
+ self.shared.rewrites.push(rewrite);
+ }
+ Some(())
+ }
+
+ fn format_last_child(
+ &mut self,
+ context: &RewriteContext<'_>,
+ shape: Shape,
+ child_shape: Shape,
+ ) -> Option<()> {
+ self.shared
+ .format_last_child(true, context, shape, child_shape)
+ }
+
+ fn join_rewrites(&self, context: &RewriteContext<'_>, child_shape: Shape) -> Option<String> {
+ self.shared.join_rewrites(context, child_shape)
+ }
+
+ fn pure_root(&mut self) -> Option<String> {
+ self.shared.pure_root()
+ }
+}
+
+// Format a chain using visual indent.
+struct ChainFormatterVisual<'a> {
+ shared: ChainFormatterShared<'a>,
+ // The extra offset from the chain's shape to the position of the `.`
+ offset: usize,
+}
+
+impl<'a> ChainFormatterVisual<'a> {
+ fn new(chain: &'a Chain) -> ChainFormatterVisual<'a> {
+ ChainFormatterVisual {
+ shared: ChainFormatterShared::new(chain),
+ offset: 0,
+ }
+ }
+}
+
+impl<'a> ChainFormatter for ChainFormatterVisual<'a> {
+ fn format_root(
+ &mut self,
+ parent: &ChainItem,
+ context: &RewriteContext<'_>,
+ shape: Shape,
+ ) -> Option<()> {
+ let parent_shape = shape.visual_indent(0);
+ let mut root_rewrite = parent.rewrite(context, parent_shape)?;
+ let multiline = root_rewrite.contains('\n');
+ self.offset = if multiline {
+ last_line_width(&root_rewrite).saturating_sub(shape.used_width())
+ } else {
+ trimmed_last_line_width(&root_rewrite)
+ };
+
+ if !multiline || parent.kind.is_block_like(context, &root_rewrite) {
+ let item = &self.shared.children[0];
+ if let ChainItemKind::Comment(..) = item.kind {
+ self.shared.rewrites.push(root_rewrite);
+ return Some(());
+ }
+ let child_shape = parent_shape
+ .visual_indent(self.offset)
+ .sub_width(self.offset)?;
+ let rewrite = item.rewrite(context, child_shape)?;
+ match wrap_str(rewrite, context.config.max_width(), shape) {
+ Some(rewrite) => root_rewrite.push_str(&rewrite),
+ None => {
+ // We couldn't fit in at the visual indent, try the last
+ // indent.
+ let rewrite = item.rewrite(context, parent_shape)?;
+ root_rewrite.push_str(&rewrite);
+ self.offset = 0;
+ }
+ }
+
+ self.shared.children = &self.shared.children[1..];
+ }
+
+ self.shared.rewrites.push(root_rewrite);
+ Some(())
+ }
+
+ fn child_shape(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<Shape> {
+ shape
+ .with_max_width(context.config)
+ .offset_left(self.offset)
+ .map(|s| s.visual_indent(0))
+ }
+
+ fn format_children(&mut self, context: &RewriteContext<'_>, child_shape: Shape) -> Option<()> {
+ for item in &self.shared.children[..self.shared.children.len() - 1] {
+ let rewrite = item.rewrite(context, child_shape)?;
+ self.shared.rewrites.push(rewrite);
+ }
+ Some(())
+ }
+
+ fn format_last_child(
+ &mut self,
+ context: &RewriteContext<'_>,
+ shape: Shape,
+ child_shape: Shape,
+ ) -> Option<()> {
+ self.shared
+ .format_last_child(false, context, shape, child_shape)
+ }
+
+ fn join_rewrites(&self, context: &RewriteContext<'_>, child_shape: Shape) -> Option<String> {
+ self.shared.join_rewrites(context, child_shape)
+ }
+
+ fn pure_root(&mut self) -> Option<String> {
+ self.shared.pure_root()
+ }
+}
+
+/// Removes try operators (`?`s) that appear in the given string. If removing
+/// them leaves an empty line, remove that line as well unless it is the first
+/// line (we need the first newline for detecting pre/post comment).
+fn trim_tries(s: &str) -> String {
+ let mut result = String::with_capacity(s.len());
+ let mut line_buffer = String::with_capacity(s.len());
+ for (kind, rich_char) in CharClasses::new(s.chars()) {
+ match rich_char.get_char() {
+ '\n' => {
+ if result.is_empty() || !line_buffer.trim().is_empty() {
+ result.push_str(&line_buffer);
+ result.push('\n')
+ }
+ line_buffer.clear();
+ }
+ '?' if kind == FullCodeCharKind::Normal => continue,
+ c => line_buffer.push(c),
+ }
+ }
+ if !line_buffer.trim().is_empty() {
+ result.push_str(&line_buffer);
+ }
+ result
+}
projects / rustc.git / blobdiff