Unindent comment on top of else

src/expr.rs

@@ -666,6 +666,7 @@ impl Rewrite for ast::Block {
 
         let mut visitor = FmtVisitor::from_codemap(context.parse_session, context.config);
         visitor.block_indent = shape.indent;
+        visitor.is_if_else_block = context.is_if_else_block;
 
         let prefix = match self.rules {
             ast::BlockCheckMode::Unsafe(..) => {
@@ -965,7 +966,10 @@ impl<'a> Rewrite for ControlFlow<'a> {
             width: block_width,
             ..shape
         };
-        let block_str = try_opt!(self.block.rewrite(context, block_shape));
+        let mut block_context = context.clone();
+        block_context.is_if_else_block = self.else_block.is_some();
+
+        let block_str = try_opt!(self.block.rewrite(&block_context, block_shape));
 
         let cond_span = if let Some(cond) = self.cond {
             cond.span

src/rewrite.rs

@@ -27,7 +27,11 @@ pub struct RewriteContext<'a> {
     pub codemap: &'a CodeMap,
     pub config: &'a Config,
     pub inside_macro: bool,
+    // Force block indent style even if we are using visual indent style.
     pub use_block: bool,
+    // When `format_if_else_cond_comment` is true, unindent the comment on top
+    // of the `else` or `else if`.
+    pub is_if_else_block: bool,
 }
 
 impl<'a> RewriteContext<'a> {

src/visitor.rs

@@ -56,6 +56,7 @@ pub struct FmtVisitor<'a> {
     pub block_indent: Indent,
     pub config: &'a Config,
     pub failed: bool,
+    pub is_if_else_block: bool,
 }
 
 impl<'a> FmtVisitor<'a> {
@@ -117,9 +118,22 @@ impl<'a> FmtVisitor<'a> {
             }
         }
 
+        let mut unindent_comment = self.is_if_else_block && !b.stmts.is_empty();
+        if unindent_comment {
+            let end_pos = source!(self, b.span).hi - brace_compensation;
+            let snippet = self.get_context()
+                .snippet(codemap::mk_sp(self.last_pos, end_pos));
+            unindent_comment = snippet.contains("//") || snippet.contains("/*");
+        }
         // FIXME: we should compress any newlines here to just one
+        if unindent_comment {
+            self.block_indent = self.block_indent.block_unindent(self.config);
+        }
         self.format_missing_with_indent(source!(self, b.span).hi - brace_compensation);
-        self.close_block();
+        if unindent_comment {
+            self.block_indent = self.block_indent.block_indent(self.config);
+        }
+        self.close_block(unindent_comment);
         self.last_pos = source!(self, b.span).hi;
     }
 
@@ -127,9 +141,11 @@ impl<'a> FmtVisitor<'a> {
     // item in the block and the closing brace to the block's level.
     // The closing brace itself, however, should be indented at a shallower
     // level.
-    fn close_block(&mut self) {
+    fn close_block(&mut self, unindent_comment: bool) {
         let total_len = self.buffer.len;
-        let chars_too_many = if self.config.hard_tabs() {
+        let chars_too_many = if unindent_comment {
+            0
+        } else if self.config.hard_tabs() {
             1
         } else {
             self.config.tab_spaces()
@@ -484,6 +500,7 @@ impl<'a> FmtVisitor<'a> {
             block_indent: Indent::empty(),
             config: config,
             failed: false,
+            is_if_else_block: false,
         }
     }
 
@@ -587,7 +604,7 @@ impl<'a> FmtVisitor<'a> {
                 self.block_indent = self.block_indent.block_indent(self.config);
                 self.walk_mod_items(m);
                 self.format_missing_with_indent(source!(self, m.inner).hi - BytePos(1));
-                self.close_block();
+                self.close_block(false);
             }
             self.last_pos = source!(self, m.inner).hi;
         } else {
@@ -611,6 +628,7 @@ impl<'a> FmtVisitor<'a> {
             config: self.config,
             inside_macro: false,
             use_block: false,
+            is_if_else_block: false,
         }
     }
 }

tests/target/unindent_if_else_cond_comment.rs

@@ -0,0 +1,27 @@
+// Comments on else block. See #1575.
+
+fn example() {
+    // `if` comment
+    if x {
+        foo();
+    // `else if` comment
+    } else if y {
+        foo();
+    // Comment on `else if`.
+    // Comment on `else if`.
+    } else if z {
+        bar();
+    /*
+     *  Multi line comment on `else if`
+     */
+    } else if xx {
+        bar();
+    /* Single line comment on `else if` */
+    } else if yy {
+        foo();
+    // `else` comment
+    } else {
+        foo();
+        // Comment at the end of `else` block
+    };
+}