New rustdoc lint to respect -Dwarnings correctly

This adds a new lint to `rustc` that is used in rustdoc when a code
block is empty or cannot be parsed as valid Rust code.

Previously this was unconditionally a warning. As such some
documentation comments were (unknowingly) abusing this to pass despite
the `-Dwarnings` used when compiling `rustc`, this should not be the
case anymore.

1 files changed, 13 insertions, 0 deletions

diff --git a/src/librustdoc/lint.rs b/src/librustdoc/lint.rs
index 1b79811d4b0..597efed56e1 100644
--- a/src/librustdoc/lint.rs
+++ b/src/librustdoc/lint.rs
@@ -157,6 +157,18 @@ declare_rustdoc_lint! {
     "detects URLs that are not hyperlinks"
 }
 
+declare_rustdoc_lint! {
+   /// The `invalid_rust_codeblock` lint detects Rust code blocks in
+   /// documentation examples that are invalid (e.g. empty, not parsable as
+   /// Rust code). This is a `rustdoc` only lint, see the documentation in the
+   /// [rustdoc book].
+   ///
+   /// [rustdoc book]: ../../../rustdoc/lints.html#invalid_rust_codeblock
+   INVALID_RUST_CODEBLOCK,
+   Warn,
+   "codeblock could not be parsed as valid Rust or is empty"
+}
+
 crate static RUSTDOC_LINTS: Lazy<Vec<&'static Lint>> = Lazy::new(|| {
     vec![
         BROKEN_INTRA_DOC_LINKS,
@@ -164,6 +176,7 @@ crate static RUSTDOC_LINTS: Lazy<Vec<&'static Lint>> = Lazy::new(|| {
         MISSING_DOC_CODE_EXAMPLES,
         PRIVATE_DOC_TESTS,
         INVALID_CODEBLOCK_ATTRIBUTES,
+        INVALID_RUST_CODEBLOCK,
         INVALID_HTML_TAGS,
         BARE_URLS,
         MISSING_CRATE_LEVEL_DOCS,