fix the doc-comment-decoration-trimming edge-case rustdoc ICE

src/libsyntax/parse/lexer/comments.rs

@@ -101,7 +101,7 @@ pub fn strip_doc_comment_decoration(comment: &str) -> String {
                     break;
                 }
             }
-            if i > line.len() {
+            if i >= line.len() {
                 can_trim = false;
             }
             if !can_trim {

src/test/rustdoc/issue-47197-blank-line-in-doc-block.rs

@@ -0,0 +1,18 @@
+// Copyright 2017 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.
+
+// @has issue_47197_blank_line_in_doc_block/fn.whose_woods_these_are_i_think_i_know.html
+
+/**
+* snow
+
+* ice
+*/
+pub fn whose_woods_these_are_i_think_i_know() {}