X-Git-Url: https://git.lizzy.rs/?a=blobdiff_plain;f=src%2Fmatches.rs;h=791f34cefe8ded442117fe601ed9c6820e7c1c94;hb=caefd218c9f6c43493c28c5cc4ea8828c494830e;hp=b97fbd8741776fca55f87901e1eb4e8fb2f83f38;hpb=88589f2ad891f115e44cab2f37993885c82c40d8;p=rust.git

diff --git a/src/matches.rs b/src/matches.rs
index b97fbd87417..791f34cefe8 100644
--- a/src/matches.rs
+++ b/src/matches.rs
@@ -13,20 +13,24 @@
 use std::iter::repeat;
 
 use config::lists::*;
-use syntax::{ast, ptr};
 use syntax::codemap::{BytePos, Span};
+use syntax::{ast, ptr};
 
 use codemap::SpanUtils;
-use comment::combine_strs_with_missing_comments;
+use comment::{combine_strs_with_missing_comments, rewrite_comment};
 use config::{Config, ControlBraceStyle, IndentStyle};
-use expr::{format_expr, is_empty_block, is_simple_block, is_unsafe_block, prefer_next_line,
-           rewrite_multiple_patterns, ExprType, RhsTactics, ToExpr};
+use expr::{
+    format_expr, is_empty_block, is_simple_block, is_unsafe_block, prefer_next_line,
+    rewrite_multiple_patterns, ExprType, RhsTactics, ToExpr,
+};
 use lists::{itemize_list, write_list, ListFormatting};
 use rewrite::{Rewrite, RewriteContext};
 use shape::Shape;
 use spanned::Spanned;
-use utils::{contains_skip, extra_offset, first_line_width, inner_attributes, last_line_extendable,
-            mk_sp, ptr_vec_to_ref_vec, trimmed_last_line_width};
+use utils::{
+    contains_skip, extra_offset, first_line_width, inner_attributes, last_line_extendable, mk_sp,
+    ptr_vec_to_ref_vec, trimmed_last_line_width,
+};
 
 /// A simple wrapper type against `ast::Arm`. Used inside `write_list()`.
 struct ArmWrapper<'a> {
@@ -64,7 +68,7 @@ fn span(&self) -> Span {
 
 impl<'a> Rewrite for ArmWrapper<'a> {
     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
-        rewrite_match_arm(context, self.arm, shape, self.is_last, self.beginning_vert)
+        rewrite_match_arm(context, self.arm, shape, self.is_last)
     }
 }
 
@@ -133,13 +137,14 @@ pub fn rewrite_match(
             Some(context.snippet(span).to_owned())
         }
     } else {
+        let span_after_cond = mk_sp(cond.span.hi(), span.hi());
         Some(format!(
             "match {}{}{{\n{}{}{}\n{}}}",
             cond_str,
             block_sep,
             inner_attrs_str,
             nested_indent_str,
-            rewrite_match_arms(context, arms, shape, span, open_brace_pos)?,
+            rewrite_match_arms(context, arms, shape, span_after_cond, open_brace_pos)?,
             shape.indent.to_string(context.config),
         ))
     }
@@ -150,7 +155,7 @@ fn arm_comma(config: &Config, body: &ast::Expr, is_last: bool) -> &'static str {
         ""
     } else if config.match_block_trailing_comma() {
         ","
-    } else if let ast::ExprKind::Block(ref block) = body.node {
+    } else if let ast::ExprKind::Block(ref block, _) = body.node {
         if let ast::BlockCheckMode::Default = block.rules {
             ""
         } else {
@@ -191,7 +196,7 @@ fn rewrite_match_arms(
 
     let arm_len = arms.len();
     let is_last_iter = repeat(false)
-        .take(arm_len.checked_sub(1).unwrap_or(0))
+        .take(arm_len.saturating_sub(1))
         .chain(repeat(true));
     let beginning_verts = collect_beginning_verts(context, arms, span);
     let items = itemize_list(
@@ -219,6 +224,7 @@ fn rewrite_match_arms(
         shape: arm_shape,
         ends_with_newline: true,
         preserve_newline: true,
+        nested: false,
         config: context.config,
     };
 
@@ -230,7 +236,6 @@ fn rewrite_match_arm(
     arm: &ast::Arm,
     shape: Shape,
     is_last: bool,
-    beginning_vert: Option<BytePos>,
 ) -> Option<String> {
     let (missing_span, attrs_str) = if !arm.attrs.is_empty() {
         if contains_skip(&arm.attrs) {
@@ -250,28 +255,27 @@ fn rewrite_match_arm(
     } else {
         (mk_sp(arm.span().lo(), arm.span().lo()), String::new())
     };
-    let pats_str = rewrite_match_pattern(
-        context,
-        &ptr_vec_to_ref_vec(&arm.pats),
-        &arm.guard,
-        beginning_vert.is_some(),
-        shape,
-    ).and_then(|pats_str| {
-        combine_strs_with_missing_comments(
-            context,
-            &attrs_str,
-            &pats_str,
-            missing_span,
-            shape,
-            false,
-        )
-    })?;
+    let pats_str =
+        rewrite_match_pattern(context, &ptr_vec_to_ref_vec(&arm.pats), &arm.guard, shape)
+            .and_then(|pats_str| {
+                combine_strs_with_missing_comments(
+                    context,
+                    &attrs_str,
+                    &pats_str,
+                    missing_span,
+                    shape,
+                    false,
+                )
+            })?;
+
+    let arrow_span = mk_sp(arm.pats.last().unwrap().span.hi(), arm.body.span.lo());
     rewrite_match_body(
         context,
         &arm.body,
         &pats_str,
         shape,
         arm.guard.is_some(),
+        arrow_span,
         is_last,
     )
 }
@@ -280,46 +284,61 @@ fn rewrite_match_pattern(
     context: &RewriteContext,
     pats: &[&ast::Pat],
     guard: &Option<ptr::P<ast::Expr>>,
-    has_beginning_vert: bool,
     shape: Shape,
 ) -> Option<String> {
     // Patterns
     // 5 = ` => {`
-    // 2 = `| `
-    let pat_shape = shape
-        .sub_width(5)?
-        .offset_left(if has_beginning_vert { 2 } else { 0 })?;
+    let pat_shape = shape.sub_width(5)?;
     let pats_str = rewrite_multiple_patterns(context, pats, pat_shape)?;
-    let beginning_vert = if has_beginning_vert { "| " } else { "" };
 
     // Guard
-    let guard_str = rewrite_guard(context, guard, shape, trimmed_last_line_width(&pats_str))?;
+    let guard_str = rewrite_guard(
+        context,
+        guard,
+        shape,
+        trimmed_last_line_width(&pats_str),
+        pats_str.contains("\n"),
+    )?;
 
-    Some(format!("{}{}{}", beginning_vert, pats_str, guard_str))
+    Some(format!("{}{}", pats_str, guard_str))
+}
+
+fn block_can_be_flattened<'a>(
+    context: &RewriteContext,
+    expr: &'a ast::Expr,
+) -> Option<&'a ast::Block> {
+    match expr.node {
+        ast::ExprKind::Block(ref block, _)
+            if !is_unsafe_block(block)
+                && is_simple_block(block, Some(&expr.attrs), context.codemap) =>
+        {
+            Some(&*block)
+        }
+        _ => None,
+    }
 }
 
 // (extend, body)
 // @extend: true if the arm body can be put next to `=>`
 // @body: flattened body, if the body is block with a single expression
 fn flatten_arm_body<'a>(context: &'a RewriteContext, body: &'a ast::Expr) -> (bool, &'a ast::Expr) {
-    match body.node {
-        ast::ExprKind::Block(ref block)
-            if !is_unsafe_block(block)
-                && is_simple_block(block, Some(&body.attrs), context.codemap) =>
-        {
-            if let ast::StmtKind::Expr(ref expr) = block.stmts[0].node {
-                (
-                    !context.config.force_multiline_blocks() && can_extend_match_arm_body(expr),
-                    &*expr,
-                )
+    if let Some(ref block) = block_can_be_flattened(context, body) {
+        if let ast::StmtKind::Expr(ref expr) = block.stmts[0].node {
+            if let ast::ExprKind::Block(..) = expr.node {
+                flatten_arm_body(context, expr)
             } else {
-                (false, &*body)
+                let can_extend_expr =
+                    !context.config.force_multiline_blocks() && can_flatten_block_around_this(expr);
+                (can_extend_expr, &*expr)
             }
+        } else {
+            (false, &*body)
         }
-        _ => (
+    } else {
+        (
             !context.config.force_multiline_blocks() && body.can_be_overflowed(context, 1),
             &*body,
-        ),
+        )
     }
 }
 
@@ -329,10 +348,11 @@ fn rewrite_match_body(
     pats_str: &str,
     shape: Shape,
     has_guard: bool,
+    arrow_span: Span,
     is_last: bool,
 ) -> Option<String> {
     let (extend, body) = flatten_arm_body(context, body);
-    let (is_block, is_empty_block) = if let ast::ExprKind::Block(ref block) = body.node {
+    let (is_block, is_empty_block) = if let ast::ExprKind::Block(ref block, _) = body.node {
         (
             true,
             is_empty_block(block, Some(&body.attrs), context.codemap),
@@ -353,24 +373,43 @@ fn rewrite_match_body(
         Some(format!("{} =>{}{}{}", pats_str, block_sep, body_str, comma))
     };
 
-    let forbid_same_line = has_guard && pats_str.contains('\n') && !is_empty_block;
     let next_line_indent = if !is_block || is_empty_block {
         shape.indent.block_indent(context.config)
     } else {
         shape.indent
     };
+
+    let forbid_same_line = has_guard && pats_str.contains('\n') && !is_empty_block;
+
+    // Look for comments between `=>` and the start of the body.
+    let arrow_comment = {
+        let arrow_snippet = context.snippet(arrow_span).trim();
+        let arrow_index = arrow_snippet.find("=>").unwrap();
+        // 2 = `=>`
+        let comment_str = arrow_snippet[arrow_index + 2..].trim();
+        if comment_str.is_empty() {
+            String::new()
+        } else {
+            rewrite_comment(comment_str, false, shape, &context.config)?
+        }
+    };
+
     let combine_next_line_body = |body_str: &str| {
+        let nested_indent_str = next_line_indent.to_string_with_newline(context.config);
+
         if is_block {
-            return Some(format!(
-                "{} =>{}{}",
-                pats_str,
-                next_line_indent.to_string_with_newline(context.config),
-                body_str
-            ));
+            let mut result = pats_str.to_owned();
+            result.push_str(" =>");
+            if !arrow_comment.is_empty() {
+                result.push_str(&nested_indent_str);
+                result.push_str(&arrow_comment);
+            }
+            result.push_str(&nested_indent_str);
+            result.push_str(&body_str);
+            return Some(result);
         }
 
         let indent_str = shape.indent.to_string_with_newline(context.config);
-        let nested_indent_str = next_line_indent.to_string_with_newline(context.config);
         let (body_prefix, body_suffix) = if context.config.match_arm_blocks() {
             let comma = if context.config.match_block_trailing_comma() {
                 ","
@@ -385,14 +424,22 @@ fn rewrite_match_body(
         let block_sep = match context.config.control_brace_style() {
             ControlBraceStyle::AlwaysNextLine => format!("{}{}", alt_block_sep, body_prefix),
             _ if body_prefix.is_empty() => "".to_owned(),
-            _ if forbid_same_line => format!("{}{}", alt_block_sep, body_prefix),
+            _ if forbid_same_line || !arrow_comment.is_empty() => {
+                format!("{}{}", alt_block_sep, body_prefix)
+            }
             _ => format!(" {}", body_prefix),
         } + &nested_indent_str;
 
-        Some(format!(
-            "{} =>{}{}{}",
-            pats_str, block_sep, body_str, body_suffix
-        ))
+        let mut result = pats_str.to_owned();
+        result.push_str(" =>");
+        if !arrow_comment.is_empty() {
+            result.push_str(&indent_str);
+            result.push_str(&arrow_comment);
+        }
+        result.push_str(&block_sep);
+        result.push_str(&body_str);
+        result.push_str(&body_suffix);
+        Some(result)
     };
 
     // Let's try and get the arm body on the same line as the condition.
@@ -400,7 +447,9 @@ fn rewrite_match_body(
     let orig_body_shape = shape
         .offset_left(extra_offset(pats_str, shape) + 4)
         .and_then(|shape| shape.sub_width(comma.len()));
-    let orig_body = if let Some(body_shape) = orig_body_shape {
+    let orig_body = if forbid_same_line || !arrow_comment.is_empty() {
+        None
+    } else if let Some(body_shape) = orig_body_shape {
         let rewrite = nop_block_collapse(
             format_expr(body, ExprType::Statement, context, body_shape),
             body_shape.width,
@@ -408,9 +457,7 @@ fn rewrite_match_body(
 
         match rewrite {
             Some(ref body_str)
-                if !forbid_same_line
-                    && (is_block
-                        || (!body_str.contains('\n') && body_str.len() <= body_shape.width)) =>
+                if is_block || (!body_str.contains('\n') && body_str.len() <= body_shape.width) =>
             {
                 return combine_orig_body(body_str);
             }
@@ -429,8 +476,7 @@ fn rewrite_match_body(
     );
     match (orig_body, next_line_body) {
         (Some(ref orig_str), Some(ref next_line_str))
-            if forbid_same_line
-                || prefer_next_line(orig_str, next_line_str, RhsTactics::Default) =>
+            if prefer_next_line(orig_str, next_line_str, RhsTactics::Default) =>
         {
             combine_next_line_body(next_line_str)
         }
@@ -454,6 +500,7 @@ fn rewrite_guard(
     // The amount of space used up on this line for the pattern in
     // the arm (excludes offset).
     pattern_width: usize,
+    multiline_pattern: bool,
 ) -> Option<String> {
     if let Some(ref guard) = *guard {
         // First try to fit the guard string on the same line as the pattern.
@@ -461,10 +508,12 @@ fn rewrite_guard(
         let cond_shape = shape
             .offset_left(pattern_width + 4)
             .and_then(|s| s.sub_width(5));
-        if let Some(cond_shape) = cond_shape {
-            if let Some(cond_str) = guard.rewrite(context, cond_shape) {
-                if !cond_str.contains('\n') || pattern_width <= context.config.tab_spaces() {
-                    return Some(format!(" if {}", cond_str));
+        if !multiline_pattern {
+            if let Some(cond_shape) = cond_shape {
+                if let Some(cond_str) = guard.rewrite(context, cond_shape) {
+                    if !cond_str.contains('\n') || pattern_width <= context.config.tab_spaces() {
+                        return Some(format!(" if {}", cond_str));
+                    }
                 }
             }
         }
@@ -493,7 +542,8 @@ fn rewrite_guard(
 fn nop_block_collapse(block_str: Option<String>, budget: usize) -> Option<String> {
     debug!("nop_block_collapse {:?} {}", block_str, budget);
     block_str.map(|block_str| {
-        if block_str.starts_with('{') && budget >= 2
+        if block_str.starts_with('{')
+            && budget >= 2
             && (block_str[1..].find(|c: char| !c.is_whitespace()).unwrap() == block_str.len() - 2)
         {
             "{}".to_owned()
@@ -503,15 +553,17 @@ fn nop_block_collapse(block_str: Option<String>, budget: usize) -> Option<String
     })
 }
 
-fn can_extend_match_arm_body(body: &ast::Expr) -> bool {
+fn can_flatten_block_around_this(body: &ast::Expr) -> bool {
     match body.node {
         // We do not allow `if` to stay on the same line, since we could easily mistake
         // `pat => if cond { ... }` and `pat if cond => { ... }`.
         ast::ExprKind::If(..) | ast::ExprKind::IfLet(..) => false,
-        ast::ExprKind::ForLoop(..)
-        | ast::ExprKind::Loop(..)
-        | ast::ExprKind::While(..)
-        | ast::ExprKind::WhileLet(..)
+        // We do not allow collapsing a block around expression with condition
+        // to avoid it being cluttered with match arm.
+        ast::ExprKind::ForLoop(..) | ast::ExprKind::While(..) | ast::ExprKind::WhileLet(..) => {
+            false
+        }
+        ast::ExprKind::Loop(..)
         | ast::ExprKind::Match(..)
         | ast::ExprKind::Block(..)
         | ast::ExprKind::Closure(..)
@@ -525,7 +577,7 @@ fn can_extend_match_arm_body(body: &ast::Expr) -> bool {
         | ast::ExprKind::Box(ref expr)
         | ast::ExprKind::Try(ref expr)
         | ast::ExprKind::Unary(_, ref expr)
-        | ast::ExprKind::Cast(ref expr, _) => can_extend_match_arm_body(expr),
+        | ast::ExprKind::Cast(ref expr, _) => can_flatten_block_around_this(expr),
         _ => false,
     }
 }