Merge pull request #1054 from sanxiyn/loop-width

Fix width computation in Loop::rewrite

src/expr.rs

@@ -504,6 +504,9 @@ fn nop_block_collapse(block_str: Option<String>, budget: usize) -> Option<String
 
 impl Rewrite for ast::Block {
     fn rewrite(&self, context: &RewriteContext, width: usize, offset: Indent) -> Option<String> {
+        // 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);
@@ -674,9 +677,15 @@ impl<'a> Rewrite for Loop<'a> {
             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, width, offset)
+            .rewrite(context, block_width, offset)
             .map(|result| {
                 format!("{}{}{}{}{}",
                         label_string,

tests/source/loop.rs

@@ -14,6 +14,8 @@ let x = loop { do_forever(); };
    while aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa > bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb {
    }
 
+    while aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa {}
+
     'b: for xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx in some_iter(arg1, arg2) {
         // do smth
     }

tests/target/loop.rs

@@ -18,6 +18,9 @@ fn main() {
     while aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa > bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb {
     }
 
+    while aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa {
+    }
+
     'b: for xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx in some_iter(arg1,
                                                                                         arg2) {
         // do smth