Separate missing_doc_code_examples from intra-doc links

These two lints have no relation other than both being nightly-only.
This allows stabilizing intra-doc links without stabilizing
missing_doc_code_examples.

Author: jyn514

src/librustdoc/passes/collect_intra_doc_links.rs

@@ -23,7 +23,7 @@ use crate::clean::*;
 use crate::core::DocContext;
 use crate::fold::DocFolder;
 use crate::html::markdown::markdown_links;
-use crate::passes::{look_for_tests, Pass};
+use crate::passes::Pass;
 
 use super::span_of_attrs;
 
@@ -508,8 +508,6 @@ impl<'a, 'tcx> DocFolder for LinkCollector<'a, 'tcx> {
         let dox = item.attrs.collapsed_doc_value().unwrap_or_else(String::new);
         trace!("got documentation '{}'", dox);
 
-        look_for_tests(&cx, &dox, &item, true);
-
         // find item's parent to resolve `Self` in item's docs below
         let parent_name = self.cx.as_local_hir_id(item.def_id).and_then(|item_hir| {
             let parent_hir = self.cx.tcx.hir().get_parent_item(item_hir);

src/librustdoc/passes/mod.rs

@@ -312,12 +312,7 @@ impl DocFolder for ImportStripper {
     }
 }
 
-pub fn look_for_tests<'tcx>(
-    cx: &DocContext<'tcx>,
-    dox: &str,
-    item: &Item,
-    check_missing_code: bool,
-) {
+pub fn look_for_tests<'tcx>(cx: &DocContext<'tcx>, dox: &str, item: &Item) {
     let hir_id = match cx.as_local_hir_id(item.def_id) {
         Some(hir_id) => hir_id,
         None => {
@@ -340,12 +335,24 @@ pub fn look_for_tests<'tcx>(
 
     find_testable_code(&dox, &mut tests, ErrorCodes::No, false, None);
 
-    if check_missing_code && tests.found_tests == 0 {
-        let sp = span_of_attrs(&item.attrs).unwrap_or(item.source.span());
-        cx.tcx.struct_span_lint_hir(lint::builtin::MISSING_DOC_CODE_EXAMPLES, hir_id, sp, |lint| {
-            lint.build("missing code example in this documentation").emit()
-        });
-    } else if !check_missing_code
+    if tests.found_tests == 0 {
+        use clean::ItemEnum::*;
+
+        let should_report = match item.inner {
+            ExternCrateItem(_, _) | ImportItem(_) | PrimitiveItem(_) | KeywordItem(_) => false,
+            _ => true,
+        };
+        if should_report {
+            debug!("reporting error for {:?} (hir_id={:?})", item, hir_id);
+            let sp = span_of_attrs(&item.attrs).unwrap_or(item.source.span());
+            cx.tcx.struct_span_lint_hir(
+                lint::builtin::MISSING_DOC_CODE_EXAMPLES,
+                hir_id,
+                sp,
+                |lint| lint.build("missing code example in this documentation").emit(),
+            );
+        }
+    } else if rustc_feature::UnstableFeatures::from_environment().is_nightly_build()
         && tests.found_tests > 0
         && !cx.renderinfo.borrow().access_levels.is_public(item.def_id)
     {

src/librustdoc/passes/private_items_doc_tests.rs

@@ -30,7 +30,7 @@ impl<'a, 'tcx> DocFolder for PrivateItemDocTestLinter<'a, 'tcx> {
         let cx = self.cx;
         let dox = item.attrs.collapsed_doc_value().unwrap_or_else(String::new);
 
-        look_for_tests(&cx, &dox, &item, false);
+        look_for_tests(&cx, &dox, &item);
 
         self.fold_item_recur(item)
     }

src/test/rustdoc-ui/lint-group.stderr

@@ -1,3 +1,16 @@
+error: missing code example in this documentation
+  --> $DIR/lint-group.rs:16:1
+   |
+LL | /// wait, this doesn't have a doctest?
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+note: the lint level is defined here
+  --> $DIR/lint-group.rs:7:9
+   |
+LL | #![deny(rustdoc)]
+   |         ^^^^^^^
+   = note: `#[deny(missing_doc_code_examples)]` implied by `#[deny(rustdoc)]`
+
 error: documentation test in private item
   --> $DIR/lint-group.rs:19:1
    |
@@ -29,18 +42,5 @@ LL | #![deny(rustdoc)]
    = note: `#[deny(intra_doc_link_resolution_failure)]` implied by `#[deny(rustdoc)]`
    = help: to escape `[` and `]` characters, add '\' before them like `\[` or `\]`
 
-error: missing code example in this documentation
-  --> $DIR/lint-group.rs:16:1
-   |
-LL | /// wait, this doesn't have a doctest?
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-note: the lint level is defined here
-  --> $DIR/lint-group.rs:7:9
-   |
-LL | #![deny(rustdoc)]
-   |         ^^^^^^^
-   = note: `#[deny(missing_doc_code_examples)]` implied by `#[deny(rustdoc)]`
-
 error: aborting due to 3 previous errors