rustdoc: correct unclosed HTML tags as generics

7 files changed, 281 insertions, 9 deletions

diff --git a/src/librustdoc/lib.rs b/src/librustdoc/lib.rs
index a7c3c0bb606..68028604fa4 100644
--- a/src/librustdoc/lib.rs
+++ b/src/librustdoc/lib.rs
@@ -5,6 +5,7 @@
 #![feature(rustc_private)]
 #![feature(array_methods)]
 #![feature(assert_matches)]
+#![feature(bool_to_option)]
 #![feature(box_patterns)]
 #![feature(control_flow_enum)]
 #![feature(box_syntax)]
diff --git a/src/librustdoc/passes/html_tags.rs b/src/librustdoc/passes/html_tags.rs
index f7a9a0899e3..7ad14bbcbb1 100644
--- a/src/librustdoc/passes/html_tags.rs
+++ b/src/librustdoc/passes/html_tags.rs
@@ -38,7 +38,7 @@ fn drop_tag(
     tags: &mut Vec<(String, Range<usize>)>,
     tag_name: String,
     range: Range<usize>,
-    f: &impl Fn(&str, &Range<usize>),
+    f: &impl Fn(&str, &Range<usize>, bool),
 ) {
     let tag_name_low = tag_name.to_lowercase();
     if let Some(pos) = tags.iter().rposition(|(t, _)| t.to_lowercase() == tag_name_low) {
@@ -59,14 +59,42 @@ fn drop_tag(
             // `tags` is used as a queue, meaning that everything after `pos` is included inside it.
             // So `<h2><h3></h2>` will look like `["h2", "h3"]`. So when closing `h2`, we will still
             // have `h3`, meaning the tag wasn't closed as it should have.
-            f(&format!("unclosed HTML tag `{}`", last_tag_name), &last_tag_span);
+            f(&format!("unclosed HTML tag `{}`", last_tag_name), &last_tag_span, true);
         }
         // Remove the `tag_name` that was originally closed
         tags.pop();
     } else {
         // It can happen for example in this case: `<h2></script></h2>` (the `h2` tag isn't required
         // but it helps for the visualization).
-        f(&format!("unopened HTML tag `{}`", tag_name), &range);
+        f(&format!("unopened HTML tag `{}`", tag_name), &range, false);
+    }
+}
+
+fn extract_path_backwards(text: &str, end_pos: usize) -> Option<usize> {
+    use rustc_lexer::{is_id_continue, is_id_start};
+    let mut current_pos = end_pos;
+    loop {
+        if current_pos >= 2 && &text[current_pos - 2..current_pos] == "::" {
+            current_pos -= 2;
+        }
+        let new_pos = text[..current_pos]
+            .char_indices()
+            .rev()
+            .take_while(|(_, c)| is_id_start(*c) || is_id_continue(*c))
+            .reduce(|_accum, item| item)
+            .and_then(|(new_pos, c)| is_id_start(c).then_some(new_pos));
+        if let Some(new_pos) = new_pos {
+            if current_pos != new_pos {
+                current_pos = new_pos;
+                continue;
+            }
+        }
+        break;
+    }
+    if current_pos == end_pos {
+        return None;
+    } else {
+        return Some(current_pos);
     }
 }
 
@@ -76,7 +104,7 @@ fn extract_html_tag(
     range: &Range<usize>,
     start_pos: usize,
     iter: &mut Peekable<CharIndices<'_>>,
-    f: &impl Fn(&str, &Range<usize>),
+    f: &impl Fn(&str, &Range<usize>, bool),
 ) {
     let mut tag_name = String::new();
     let mut is_closing = false;
@@ -140,7 +168,7 @@ fn extract_tags(
     text: &str,
     range: Range<usize>,
     is_in_comment: &mut Option<Range<usize>>,
-    f: &impl Fn(&str, &Range<usize>),
+    f: &impl Fn(&str, &Range<usize>, bool),
 ) {
     let mut iter = text.char_indices().peekable();
 
@@ -178,14 +206,49 @@ impl<'a, 'tcx> DocVisitor for InvalidHtmlTagsLinter<'a, 'tcx> {
         };
         let dox = item.attrs.collapsed_doc_value().unwrap_or_default();
         if !dox.is_empty() {
-            let report_diag = |msg: &str, range: &Range<usize>| {
+            let report_diag = |msg: &str, range: &Range<usize>, is_open_tag: bool| {
                 let sp = match super::source_span_for_markdown_range(tcx, &dox, range, &item.attrs)
                 {
                     Some(sp) => sp,
                     None => item.attr_span(tcx),
                 };
                 tcx.struct_span_lint_hir(crate::lint::INVALID_HTML_TAGS, hir_id, sp, |lint| {
-                    lint.build(msg).emit()
+                    use rustc_lint_defs::Applicability;
+                    let mut diag = lint.build(msg);
+                    // If a tag looks like `<this>`, it might actually be a generic.
+                    // We don't try to detect stuff `<like, this>` because that's not valid HTML,
+                    // and we don' try to detect stuff `<like this>` because that's not valid Rust.
+                    if let Some(Some(generics_start)) = (is_open_tag
+                        && &dox[range.end - 1..range.end] == ">")
+                        .then(|| extract_path_backwards(&dox, range.start))
+                    {
+                        let generics_sp = match super::source_span_for_markdown_range(
+                            tcx,
+                            &dox,
+                            &(generics_start..range.end),
+                            &item.attrs,
+                        ) {
+                            Some(sp) => sp,
+                            None => item.attr_span(tcx),
+                        };
+                        if let Ok(generics_snippet) =
+                            tcx.sess.source_map().span_to_snippet(generics_sp)
+                        {
+                            // short form is chosen here because ``Vec<i32>`` would be confusing.
+                            diag.span_suggestion_short(
+                                generics_sp,
+                                "try marking as source code with `backticks`",
+                                format!("`{}`", generics_snippet),
+                                Applicability::MachineApplicable,
+                            );
+                        } else {
+                            diag.span_help(
+                                generics_sp,
+                                "try marking as source code with `backticks`",
+                            );
+                        }
+                    }
+                    diag.emit()
                 });
             };
 
@@ -210,11 +273,11 @@ impl<'a, 'tcx> DocVisitor for InvalidHtmlTagsLinter<'a, 'tcx> {
                 let t = t.to_lowercase();
                 !ALLOWED_UNCLOSED.contains(&t.as_str())
             }) {
-                report_diag(&format!("unclosed HTML tag `{}`", tag), range);
+                report_diag(&format!("unclosed HTML tag `{}`", tag), range, true);
             }
 
             if let Some(range) = is_in_comment {
-                report_diag("Unclosed HTML comment", &range);
+                report_diag("Unclosed HTML comment", &range, false);
             }
         }
 
diff --git a/src/test/rustdoc-ui/suggestions/html-as-generics-no-suggestions.rs b/src/test/rustdoc-ui/suggestions/html-as-generics-no-suggestions.rs
new file mode 100644
index 00000000000..744b3071f1b
--- /dev/null
+++ b/src/test/rustdoc-ui/suggestions/html-as-generics-no-suggestions.rs
@@ -0,0 +1,38 @@
+#![deny(rustdoc::invalid_html_tags)]
+
+/// This Vec<32> thing!
+// Numbers aren't valid HTML tags, so no error.
+pub struct ConstGeneric;
+
+/// This Vec<i32, i32> thing!
+// HTML tags cannot contain commas, so no error.
+pub struct MultipleGenerics;
+
+/// This Vec<i32 class="test"> thing!
+//~^ERROR unclosed HTML tag `i32`
+// HTML attributes shouldn't be treated as Rust syntax, so no suggestions.
+pub struct TagWithAttributes;
+
+/// This Vec<i32></i32> thing!
+// There should be no error, and no suggestion, since the tags are balanced.
+pub struct DoNotWarnOnMatchingTags;
+
+/// This Vec</i32> thing!
+//~^ERROR unopened HTML tag `i32`
+// This should produce an error, but no suggestion.
+pub struct EndTagsAreNotValidRustSyntax;
+
+/// This 123<i32> thing!
+//~^ERROR unclosed HTML tag `i32`
+// This should produce an error, but no suggestion.
+pub struct NumbersAreNotPaths;
+
+/// This Vec:<i32> thing!
+//~^ERROR unclosed HTML tag `i32`
+// This should produce an error, but no suggestion.
+pub struct InvalidTurbofish;
+
+/// This [link](https://rust-lang.org)<i32> thing!
+//~^ERROR unclosed HTML tag `i32`
+// This should produce an error, but no suggestion.
+pub struct BareTurbofish;
diff --git a/src/test/rustdoc-ui/suggestions/html-as-generics-no-suggestions.stderr b/src/test/rustdoc-ui/suggestions/html-as-generics-no-suggestions.stderr
new file mode 100644
index 00000000000..832b8b2cac7
--- /dev/null
+++ b/src/test/rustdoc-ui/suggestions/html-as-generics-no-suggestions.stderr
@@ -0,0 +1,38 @@
+error: unclosed HTML tag `i32`
+  --> $DIR/html-as-generics-no-suggestions.rs:11:13
+   |
+LL | /// This Vec<i32 class="test"> thing!
+   |             ^^^^
+   |
+note: the lint level is defined here
+  --> $DIR/html-as-generics-no-suggestions.rs:1:9
+   |
+LL | #![deny(rustdoc::invalid_html_tags)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: unopened HTML tag `i32`
+  --> $DIR/html-as-generics-no-suggestions.rs:20:13
+   |
+LL | /// This Vec</i32> thing!
+   |             ^^^^^^
+
+error: unclosed HTML tag `i32`
+  --> $DIR/html-as-generics-no-suggestions.rs:25:13
+   |
+LL | /// This 123<i32> thing!
+   |             ^^^^^
+
+error: unclosed HTML tag `i32`
+  --> $DIR/html-as-generics-no-suggestions.rs:30:14
+   |
+LL | /// This Vec:<i32> thing!
+   |              ^^^^^
+
+error: unclosed HTML tag `i32`
+  --> $DIR/html-as-generics-no-suggestions.rs:35:39
+   |
+LL | /// This [link](https://rust-lang.org)<i32> thing!
+   |                                       ^^^^^
+
+error: aborting due to 5 previous errors
+
diff --git a/src/test/rustdoc-ui/suggestions/html-as-generics.fixed b/src/test/rustdoc-ui/suggestions/html-as-generics.fixed
new file mode 100644
index 00000000000..04bdd038993
--- /dev/null
+++ b/src/test/rustdoc-ui/suggestions/html-as-generics.fixed
@@ -0,0 +1,38 @@
+// run-rustfix
+#![deny(rustdoc::invalid_html_tags)]
+
+/// This `Vec<i32>` thing!
+//~^ERROR unclosed HTML tag `i32`
+//~|HELP try marking as source
+//~|SUGGESTION `Vec<i32>`
+pub struct Generic;
+
+/// This `vec::Vec<i32>` thing!
+//~^ERROR unclosed HTML tag `i32`
+//~|HELP try marking as source
+//~|SUGGESTION `vec::Vec<i32>`
+pub struct GenericPath;
+
+/// This `i32<i32>` thing!
+//~^ERROR unclosed HTML tag `i32`
+//~|HELP try marking as source
+//~|SUGGESTION `i32<i32>`
+pub struct PathsCanContainTrailingNumbers;
+
+/// This `Vec::<i32>` thing!
+//~^ERROR unclosed HTML tag `i32`
+//~|HELP try marking as source
+//~|SUGGESTION `Vec::<i32>`
+pub struct Turbofish;
+
+/// This [link](https://rust-lang.org)`::<i32>` thing!
+//~^ERROR unclosed HTML tag `i32`
+//~|HELP try marking as source
+//~|SUGGESTION `::<i32>`
+pub struct BareTurbofish;
+
+/// This <span>`Vec::<i32>`</span> thing!
+//~^ERROR unclosed HTML tag `i32`
+//~|HELP try marking as source
+//~|SUGGESTION `Vec::<i32>`
+pub struct Nested;
diff --git a/src/test/rustdoc-ui/suggestions/html-as-generics.rs b/src/test/rustdoc-ui/suggestions/html-as-generics.rs
new file mode 100644
index 00000000000..28e50c00738
--- /dev/null
+++ b/src/test/rustdoc-ui/suggestions/html-as-generics.rs
@@ -0,0 +1,38 @@
+// run-rustfix
+#![deny(rustdoc::invalid_html_tags)]
+
+/// This Vec<i32> thing!
+//~^ERROR unclosed HTML tag `i32`
+//~|HELP try marking as source
+//~|SUGGESTION `Vec<i32>`
+pub struct Generic;
+
+/// This vec::Vec<i32> thing!
+//~^ERROR unclosed HTML tag `i32`
+//~|HELP try marking as source
+//~|SUGGESTION `vec::Vec<i32>`
+pub struct GenericPath;
+
+/// This i32<i32> thing!
+//~^ERROR unclosed HTML tag `i32`
+//~|HELP try marking as source
+//~|SUGGESTION `i32<i32>`
+pub struct PathsCanContainTrailingNumbers;
+
+/// This Vec::<i32> thing!
+//~^ERROR unclosed HTML tag `i32`
+//~|HELP try marking as source
+//~|SUGGESTION `Vec::<i32>`
+pub struct Turbofish;
+
+/// This [link](https://rust-lang.org)::<i32> thing!
+//~^ERROR unclosed HTML tag `i32`
+//~|HELP try marking as source
+//~|SUGGESTION `::<i32>`
+pub struct BareTurbofish;
+
+/// This <span>Vec::<i32></span> thing!
+//~^ERROR unclosed HTML tag `i32`
+//~|HELP try marking as source
+//~|SUGGESTION `Vec::<i32>`
+pub struct Nested;
diff --git a/src/test/rustdoc-ui/suggestions/html-as-generics.stderr b/src/test/rustdoc-ui/suggestions/html-as-generics.stderr
new file mode 100644
index 00000000000..c0a1603bc66
--- /dev/null
+++ b/src/test/rustdoc-ui/suggestions/html-as-generics.stderr
@@ -0,0 +1,56 @@
+error: unclosed HTML tag `i32`
+  --> $DIR/html-as-generics.rs:4:13
+   |
+LL | /// This Vec<i32> thing!
+   |          ---^^^^^
+   |          |
+   |          help: try marking as source code with `backticks`
+   |
+note: the lint level is defined here
+  --> $DIR/html-as-generics.rs:2:9
+   |
+LL | #![deny(rustdoc::invalid_html_tags)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: unclosed HTML tag `i32`
+  --> $DIR/html-as-generics.rs:10:18
+   |
+LL | /// This vec::Vec<i32> thing!
+   |          --------^^^^^
+   |          |
+   |          help: try marking as source code with `backticks`
+
+error: unclosed HTML tag `i32`
+  --> $DIR/html-as-generics.rs:16:13
+   |
+LL | /// This i32<i32> thing!
+   |          ---^^^^^
+   |          |
+   |          help: try marking as source code with `backticks`
+
+error: unclosed HTML tag `i32`
+  --> $DIR/html-as-generics.rs:22:15
+   |
+LL | /// This Vec::<i32> thing!
+   |          -----^^^^^
+   |          |
+   |          help: try marking as source code with `backticks`
+
+error: unclosed HTML tag `i32`
+  --> $DIR/html-as-generics.rs:28:41
+   |
+LL | /// This [link](https://rust-lang.org)::<i32> thing!
+   |                                       --^^^^^
+   |                                       |
+   |                                       help: try marking as source code with `backticks`
+
+error: unclosed HTML tag `i32`
+  --> $DIR/html-as-generics.rs:34:21
+   |
+LL | /// This <span>Vec::<i32></span> thing!
+   |                -----^^^^^
+   |                |
+   |                help: try marking as source code with `backticks`
+
+error: aborting due to 6 previous errors
+