X-Git-Url: https://git.lizzy.rs/?a=blobdiff_plain;f=src%2Fchains.rs;h=c7acf19ee0cea6e42bb41891bb371a394b829b23;hb=66c27c9161b2aa70c2902807be12952bd4a0a62b;hp=9d0e8c7c6d282f9d8182d2ae2f1f8ae667727f9e;hpb=49945a14f7a566dd12993910171e9bdd9b6c32fb;p=rust.git

diff --git a/src/chains.rs b/src/chains.rs
index 9d0e8c7c6d2..c7acf19ee0c 100644
--- a/src/chains.rs
+++ b/src/chains.rs
@@ -1,15 +1,5 @@
-// 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.
-
-//! Formatting of chained expressions, i.e. expressions which are chained by
-//! dots: struct and enum field access, method calls, and try shorthand (?).
+//! 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
@@ -26,7 +16,7 @@
 //! following values of `chain_indent`:
 //! Block:
 //!
-//! ```ignore
+//! ```text
 //! let foo = {
 //!     aaaa;
 //!     bbb;
@@ -37,7 +27,7 @@
 //!
 //! Visual:
 //!
-//! ```ignore
+//! ```text
 //! let foo = {
 //!               aaaa;
 //!               bbb;
@@ -51,7 +41,7 @@
 //! the braces.
 //! Block:
 //!
-//! ```ignore
+//! ```text
 //! let a = foo.bar
 //!     .baz()
 //!     .qux
@@ -59,32 +49,36 @@
 //!
 //! Visual:
 //!
-//! ```ignore
+//! ```text
 //! let a = foo.bar
 //!            .baz()
 //!            .qux
 //! ```
 
-use codemap::SpanUtils;
-use comment::rewrite_comment;
-use config::IndentStyle;
-use expr::rewrite_call;
-use macros::convert_try_mac;
-use rewrite::{Rewrite, RewriteContext};
-use shape::Shape;
-use utils::{
-    first_line_width, last_line_extendable, last_line_width, mk_sp, trimmed_last_line_width,
-    wrap_str,
-};
-
 use std::borrow::Cow;
 use std::cmp::min;
-use std::iter;
 
-use syntax::codemap::Span;
+use syntax::source_map::{BytePos, Span};
 use syntax::{ast, ptr};
 
-pub fn rewrite_chain(expr: &ast::Expr, context: &RewriteContext, shape: Shape) -> Option<String> {
+use crate::comment::{rewrite_comment, CharClasses, FullCodeCharKind, RichChar};
+use crate::config::IndentStyle;
+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);
 
@@ -97,6 +91,12 @@ pub fn rewrite_chain(expr: &ast::Expr, context: &RewriteContext, shape: Shape) -
     chain.rewrite(context, shape)
 }
 
+#[derive(Debug)]
+enum CommentPosition {
+    Back,
+    Top,
+}
+
 // An expression plus trailing `?`s to be formatted together.
 #[derive(Debug)]
 struct ChainItem {
@@ -118,17 +118,19 @@ enum ChainItemKind {
     ),
     StructField(ast::Ident),
     TupleField(ast::Ident, bool),
-    Comment,
+    Await,
+    Comment(String, CommentPosition),
 }
 
 impl ChainItemKind {
-    fn is_block_like(&self, context: &RewriteContext, reps: &str) -> bool {
+    fn is_block_like(&self, context: &RewriteContext<'_>, reps: &str) -> bool {
         match self {
-            ChainItemKind::Parent(ref expr) => is_block_expr(context, expr, reps),
-            ChainItemKind::MethodCall(..) => reps.contains('\n'),
-            ChainItemKind::StructField(..)
+            ChainItemKind::Parent(ref expr) => utils::is_block_expr(context, expr, reps),
+            ChainItemKind::MethodCall(..)
+            | ChainItemKind::StructField(..)
             | ChainItemKind::TupleField(..)
-            | ChainItemKind::Comment => false,
+            | ChainItemKind::Await
+            | ChainItemKind::Comment(..) => false,
         }
     }
 
@@ -141,7 +143,7 @@ fn is_tup_field_access(expr: &ast::Expr) -> bool {
         }
     }
 
-    fn from_ast(context: &RewriteContext, expr: &ast::Expr) -> (ChainItemKind, Span) {
+    fn from_ast(context: &RewriteContext<'_>, expr: &ast::Expr) -> (ChainItemKind, Span) {
         let (kind, span) = match expr.node {
             ast::ExprKind::MethodCall(ref segment, ref expressions) => {
                 let types = if let Some(ref generic_args) = segment.args {
@@ -166,6 +168,10 @@ fn from_ast(context: &RewriteContext, expr: &ast::Expr) -> (ChainItemKind, Span)
                 let span = mk_sp(nested.span.hi(), field.span.hi());
                 (kind, span)
             }
+            ast::ExprKind::Await(ast::AwaitOrigin::FieldLike, ref nested) => {
+                let span = mk_sp(nested.span.hi(), expr.span.hi());
+                (ChainItemKind::Await, span)
+            }
             _ => return (ChainItemKind::Parent(expr.clone()), expr.span),
         };
 
@@ -176,37 +182,37 @@ fn from_ast(context: &RewriteContext, expr: &ast::Expr) -> (ChainItemKind, Span)
 }
 
 impl Rewrite for ChainItem {
-    fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
+    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!(".{}", ident.name),
-            ChainItemKind::TupleField(ident, nested) => {
-                format!("{}.{}", if nested { " " } else { "" }, ident.name)
+            ChainItemKind::StructField(ident) => format!(".{}", rewrite_ident(context, ident)),
+            ChainItemKind::TupleField(ident, nested) => format!(
+                "{}.{}",
+                if nested { " " } else { "" },
+                rewrite_ident(context, ident)
+            ),
+            ChainItemKind::Await => ".await".to_owned(),
+            ChainItemKind::Comment(ref comment, _) => {
+                rewrite_comment(comment, false, shape, context.config)?
             }
-            ChainItemKind::Comment => rewrite_comment(
-                context.snippet(self.span).trim(),
-                false,
-                shape,
-                context.config,
-            )?,
         };
         Some(format!("{}{}", rewrite, "?".repeat(self.tries)))
     }
 }
 
 impl ChainItem {
-    fn new(context: &RewriteContext, expr: &ast::Expr, tries: usize) -> 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) -> ChainItem {
+    fn comment(span: Span, comment: String, pos: CommentPosition) -> ChainItem {
         ChainItem {
-            kind: ChainItemKind::Comment,
+            kind: ChainItemKind::Comment(comment, pos),
             tries: 0,
             span,
         }
@@ -214,7 +220,7 @@ fn comment(span: Span) -> ChainItem {
 
     fn is_comment(&self) -> bool {
         match self.kind {
-            ChainItemKind::Comment => true,
+            ChainItemKind::Comment(..) => true,
             _ => false,
         }
     }
@@ -224,7 +230,7 @@ fn rewrite_method_call(
         types: &[ast::GenericArg],
         args: &[ptr::P<ast::Expr>],
         span: Span,
-        context: &RewriteContext,
+        context: &RewriteContext<'_>,
         shape: Shape,
     ) -> Option<String> {
         let type_str = if types.is_empty() {
@@ -237,7 +243,7 @@ fn rewrite_method_call(
 
             format!("::<{}>", type_list.join(", "))
         };
-        let callee_str = format!(".{}{}", method_name, type_str);
+        let callee_str = format!(".{}{}", rewrite_ident(context, method_name), type_str);
         rewrite_call(context, &callee_str, &args[1..], span, shape)
     }
 }
@@ -249,7 +255,7 @@ struct Chain {
 }
 
 impl Chain {
-    fn from_ast(expr: &ast::Expr, context: &RewriteContext) -> 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
@@ -269,20 +275,101 @@ 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_hi = parent.span.hi();
-        for chain_item in rev_children.into_iter().rev() {
-            let comment_span = mk_sp(prev_hi, chain_item.span.lo());
+        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 !(context.config.use_try_shorthand()
-                || comment_snippet.trim().is_empty()
-                || is_tries(comment_snippet.trim()))
-            {
-                children.push(ChainItem::comment(comment_span));
+            if !is_tries(comment_snippet.trim()) {
+                handle_post_comment(
+                    comment_span,
+                    comment_snippet,
+                    &mut prev_span_end,
+                    &mut children,
+                );
             }
-            prev_hi = chain_item.span.hi();
+        }
+        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 }
@@ -290,7 +377,7 @@ fn is_tries(s: &str) -> bool {
 
     // 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> {
+    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) {
@@ -302,19 +389,21 @@ fn make_subexpr_list(expr: &ast::Expr, context: &RewriteContext) -> Vec<ast::Exp
 
     // 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> {
+    fn pop_expr_chain(expr: &ast::Expr, context: &RewriteContext<'_>) -> Option<ast::Expr> {
         match expr.node {
             ast::ExprKind::MethodCall(_, ref expressions) => {
                 Some(Self::convert_try(&expressions[0], context))
             }
-            ast::ExprKind::Field(ref subexpr, _) | ast::ExprKind::Try(ref subexpr) => {
+            ast::ExprKind::Field(ref subexpr, _)
+            | ast::ExprKind::Try(ref subexpr)
+            | ast::ExprKind::Await(ast::AwaitOrigin::FieldLike, ref subexpr) => {
                 Some(Self::convert_try(subexpr, context))
             }
             _ => None,
         }
     }
 
-    fn convert_try(expr: &ast::Expr, context: &RewriteContext) -> ast::Expr {
+    fn convert_try(expr: &ast::Expr, context: &RewriteContext<'_>) -> ast::Expr {
         match expr.node {
             ast::ExprKind::Mac(ref mac) if context.config.use_try_shorthand() => {
                 if let Some(subexpr) = convert_try_mac(mac, context) {
@@ -329,12 +418,16 @@ fn convert_try(expr: &ast::Expr, context: &RewriteContext) -> ast::Expr {
 }
 
 impl Rewrite for Chain {
-    fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
+    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<ChainFormatter>,
-            IndentStyle::Visual => Box::new(ChainFormatterVisual::new(self)) as Box<ChainFormatter>,
+            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)?;
@@ -361,7 +454,7 @@ 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()
     // ```
@@ -369,18 +462,18 @@ trait ChainFormatter {
     fn format_root(
         &mut self,
         parent: &ChainItem,
-        context: &RewriteContext,
+        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 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,
+        context: &RewriteContext<'_>,
         shape: Shape,
         child_shape: Shape,
     ) -> Option<()>;
-    fn join_rewrites(&self, context: &RewriteContext, child_shape: Shape) -> Option<String>;
+    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>;
 }
@@ -423,7 +516,7 @@ fn pure_root(&mut self) -> Option<String> {
     // 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,
@@ -432,7 +525,7 @@ fn pure_root(&mut self) -> Option<String> {
     // ```
     //
     // A chain without overflowing the last child (in vertical layout):
-    // ```
+    // ```text
     // parent
     //     .child1
     //     .child2
@@ -440,8 +533,8 @@ fn pure_root(&mut self) -> Option<String> {
     // ```
     //
     // In particular, overflowing is effective when the last child is a method with a multi-lined
-    // block-like argument (e.g. closure):
-    // ```
+    // 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);
@@ -454,7 +547,7 @@ fn pure_root(&mut self) -> Option<String> {
     fn format_last_child(
         &mut self,
         may_extend: bool,
-        context: &RewriteContext,
+        context: &RewriteContext<'_>,
         shape: Shape,
         child_shape: Shape,
     ) -> Option<()> {
@@ -466,13 +559,17 @@ fn format_last_child(
         let almost_total = if extendable {
             prev_last_line_width
         } else {
-            self.rewrites.iter().fold(0, |a, b| a + b.len())
+            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);
+        }
+        .saturating_sub(almost_total);
 
         let all_in_one_line = !self.children.iter().any(ChainItem::is_comment)
             && self.rewrites.iter().all(|s| !s.contains('\n'))
@@ -489,7 +586,15 @@ fn format_last_child(
         if all_in_one_line || extendable {
             // First we try to 'overflow' the last child and see if it looks better than using
             // vertical layout.
-            if let Some(one_line_shape) = last_shape.offset_left(almost_total) {
+            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.
@@ -527,17 +632,18 @@ fn format_last_child(
             }
         }
 
+        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,
-        block_like_iter: impl Iterator<Item = bool>,
-    ) -> Option<String> {
+    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("")
@@ -551,13 +657,14 @@ fn join_rewrites(
 
         let mut rewrite_iter = self.rewrites.iter();
         let mut result = rewrite_iter.next().unwrap().clone();
-
-        for (rewrite, prev_is_block_like) in rewrite_iter.zip(block_like_iter) {
-            if !prev_is_block_like {
-                result.push_str(&connector);
-            } else if rewrite.starts_with('/') {
-                // This is comment, add a space before it.
-                result.push(' ');
+        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);
         }
@@ -569,15 +676,14 @@ fn join_rewrites(
 // Formats a chain using block indent.
 struct ChainFormatterBlock<'a> {
     shared: ChainFormatterShared<'a>,
-    // For each rewrite, whether the corresponding item is block-like.
-    is_block_like: Vec<bool>,
+    root_ends_with_block: bool,
 }
 
 impl<'a> ChainFormatterBlock<'a> {
     fn new(chain: &'a Chain) -> ChainFormatterBlock<'a> {
         ChainFormatterBlock {
             shared: ChainFormatterShared::new(chain),
-            is_block_like: Vec::with_capacity(chain.children.len() + 1),
+            root_ends_with_block: false,
         }
     }
 }
@@ -586,7 +692,7 @@ impl<'a> ChainFormatter for ChainFormatterBlock<'a> {
     fn format_root(
         &mut self,
         parent: &ChainItem,
-        context: &RewriteContext,
+        context: &RewriteContext<'_>,
         shape: Shape,
     ) -> Option<()> {
         let mut root_rewrite: String = parent.rewrite(context, shape)?;
@@ -596,7 +702,7 @@ fn format_root(
 
         while root_rewrite.len() <= tab_width && !root_rewrite.contains('\n') {
             let item = &self.shared.children[0];
-            if let ChainItemKind::Comment = item.kind {
+            if let ChainItemKind::Comment(..) = item.kind {
                 break;
             }
             let shape = shape.offset_left(root_rewrite.len())?;
@@ -605,33 +711,32 @@ fn format_root(
                 None => break,
             }
 
-            root_ends_with_block = item.kind.is_block_like(context, &root_rewrite);
+            root_ends_with_block = last_line_extendable(&root_rewrite);
 
             self.shared.children = &self.shared.children[1..];
             if self.shared.children.is_empty() {
                 break;
             }
         }
-        self.is_block_like.push(root_ends_with_block);
         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> {
+    fn child_shape(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<Shape> {
         Some(
-            if self.is_block_like[0] {
+            if self.root_ends_with_block {
                 shape.block_indent(0)
             } else {
                 shape.block_indent(context.config.tab_spaces())
-            }.with_max_width(context.config),
+            }
+            .with_max_width(context.config),
         )
     }
 
-    fn format_children(&mut self, context: &RewriteContext, child_shape: Shape) -> Option<()> {
+    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.is_block_like
-                .push(item.kind.is_block_like(context, &rewrite));
             self.shared.rewrites.push(rewrite);
         }
         Some(())
@@ -639,7 +744,7 @@ fn format_children(&mut self, context: &RewriteContext, child_shape: Shape) -> O
 
     fn format_last_child(
         &mut self,
-        context: &RewriteContext,
+        context: &RewriteContext<'_>,
         shape: Shape,
         child_shape: Shape,
     ) -> Option<()> {
@@ -647,9 +752,8 @@ fn format_last_child(
             .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, self.is_block_like.iter().cloned())
+    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> {
@@ -677,7 +781,7 @@ impl<'a> ChainFormatter for ChainFormatterVisual<'a> {
     fn format_root(
         &mut self,
         parent: &ChainItem,
-        context: &RewriteContext,
+        context: &RewriteContext<'_>,
         shape: Shape,
     ) -> Option<()> {
         let parent_shape = shape.visual_indent(0);
@@ -691,7 +795,7 @@ fn format_root(
 
         if !multiline || parent.kind.is_block_like(context, &root_rewrite) {
             let item = &self.shared.children[0];
-            if let ChainItemKind::Comment = item.kind {
+            if let ChainItemKind::Comment(..) = item.kind {
                 self.shared.rewrites.push(root_rewrite);
                 return Some(());
             }
@@ -717,14 +821,14 @@ fn format_root(
         Some(())
     }
 
-    fn child_shape(&self, context: &RewriteContext, shape: Shape) -> Option<Shape> {
+    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<()> {
+    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);
@@ -734,7 +838,7 @@ fn format_children(&mut self, context: &RewriteContext, child_shape: Shape) -> O
 
     fn format_last_child(
         &mut self,
-        context: &RewriteContext,
+        context: &RewriteContext<'_>,
         shape: Shape,
         child_shape: Shape,
     ) -> Option<()> {
@@ -742,9 +846,8 @@ fn format_last_child(
             .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, iter::repeat(false))
+    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> {
@@ -752,33 +855,27 @@ fn pure_root(&mut self) -> Option<String> {
     }
 }
 
-// States whether an expression's last line exclusively consists of closing
-// parens, braces, and brackets in its idiomatic formatting.
-fn is_block_expr(context: &RewriteContext, expr: &ast::Expr, repr: &str) -> bool {
-    match expr.node {
-        ast::ExprKind::Mac(..)
-        | ast::ExprKind::Call(..)
-        | ast::ExprKind::MethodCall(..)
-        | ast::ExprKind::Struct(..)
-        | ast::ExprKind::While(..)
-        | ast::ExprKind::WhileLet(..)
-        | ast::ExprKind::If(..)
-        | ast::ExprKind::IfLet(..)
-        | ast::ExprKind::Block(..)
-        | ast::ExprKind::Loop(..)
-        | ast::ExprKind::ForLoop(..)
-        | ast::ExprKind::Match(..) => repr.contains('\n'),
-        ast::ExprKind::Paren(ref expr)
-        | ast::ExprKind::Binary(_, _, ref expr)
-        | ast::ExprKind::Index(_, ref expr)
-        | ast::ExprKind::Unary(_, ref expr)
-        | ast::ExprKind::Closure(_, _, _, _, ref expr, _)
-        | ast::ExprKind::Try(ref expr)
-        | ast::ExprKind::Yield(Some(ref expr)) => is_block_expr(context, expr, repr),
-        // This can only be a string lit
-        ast::ExprKind::Lit(_) => {
-            repr.contains('\n') && trimmed_last_line_width(repr) <= context.config.tab_spaces()
+/// 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),
         }
-        _ => false,
     }
+    if !line_buffer.trim().is_empty() {
+        result.push_str(&line_buffer);
+    }
+    result
 }