From aa3d7a4e6e62aad4f96d7f0b547853641d980eca Mon Sep 17 00:00:00 2001
From: QuietMisdreavus <grey@quietmisdreavus.net>
Date: Wed, 14 Nov 2018 18:14:31 -0600
Subject: [PATCH] properly calculate spans for intra-doc link resolution errors

---
 .../passes/collect_intra_doc_links.rs         |  2 +-
 .../rustdoc-ui/intra-link-span-ice-55723.rs   | 24 +++++++++++++++++++
 .../intra-link-span-ice-55723.stderr          | 13 ++++++++++
 3 files changed, 38 insertions(+), 1 deletion(-)
 create mode 100644 src/test/rustdoc-ui/intra-link-span-ice-55723.rs
 create mode 100644 src/test/rustdoc-ui/intra-link-span-ice-55723.stderr

diff --git a/src/librustdoc/passes/collect_intra_doc_links.rs b/src/librustdoc/passes/collect_intra_doc_links.rs
index a780322e85e86..f25aa000d803d 100644
--- a/src/librustdoc/passes/collect_intra_doc_links.rs
+++ b/src/librustdoc/passes/collect_intra_doc_links.rs
@@ -527,7 +527,7 @@ fn resolution_failure(
                 doc_comment_padding +
                     // Each subsequent leading whitespace and `///`
                     code_dox.lines().skip(1).take(line_offset - 1).fold(0, |sum, line| {
-                        sum + doc_comment_padding + line.len() - line.trim().len()
+                        sum + doc_comment_padding + line.len() - line.trim_start().len()
                     })
             };
 
diff --git a/src/test/rustdoc-ui/intra-link-span-ice-55723.rs b/src/test/rustdoc-ui/intra-link-span-ice-55723.rs
new file mode 100644
index 0000000000000..12e59a4813f85
--- /dev/null
+++ b/src/test/rustdoc-ui/intra-link-span-ice-55723.rs
@@ -0,0 +1,24 @@
+// Copyright 2018 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.
+
+// ignore-tidy-end-whitespace
+
+#![deny(intra_doc_link_resolution_failure)]
+
+// An error in calculating spans while reporting intra-doc link resolution errors caused rustdoc to
+// attempt to slice in the middle of a multibyte character. See
+// https://github.com/rust-lang/rust/issues/55723
+
+/// ## For example:
+///  
+/// （arr[i]）
+pub fn test_ice() {
+    unimplemented!();
+}
diff --git a/src/test/rustdoc-ui/intra-link-span-ice-55723.stderr b/src/test/rustdoc-ui/intra-link-span-ice-55723.stderr
new file mode 100644
index 0000000000000..7ae6af4a75e8c
--- /dev/null
+++ b/src/test/rustdoc-ui/intra-link-span-ice-55723.stderr
@@ -0,0 +1,13 @@
+error: `[i]` cannot be resolved, ignoring it...
+  --> $DIR/intra-link-span-ice-55723.rs:21:10
+   |
+LL | /// （arr[i]）
+   |           ^ cannot be resolved, ignoring
+   |
+note: lint level defined here
+  --> $DIR/intra-link-span-ice-55723.rs:13:9
+   |
+LL | #![deny(intra_doc_link_resolution_failure)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = help: to escape `[` and `]` characters, just add '/' before them like `/[` or `/]`
+