fix(lint): std_instead_of_core false positive for core::io

Author: bushrat011899

clippy_lints/src/std_instead_of_core.rs

@@ -237,27 +237,34 @@ fn get_first_segment<'tcx>(path: &Path<'tcx>) -> Option<&'tcx PathSegment<'tcx>>
 ///
 /// Does not catch individually moved items
 fn is_stable(cx: &LateContext<'_>, mut def_id: DefId, msrv: Msrv) -> bool {
-    loop {
-        if let Some(stability) = cx.tcx.lookup_stability(def_id)
-            && let StabilityLevel::Stable {
+    core::iter::once(def_id)
+        .chain(core::iter::from_fn(|| {
+            def_id = cx.tcx.opt_parent(def_id)?;
+            Some(def_id)
+        }))
+        .find_map(|def_id| match cx.tcx.lookup_stability(def_id)?.level {
+            StabilityLevel::Unstable { .. } => Some(false),
+            StabilityLevel::Stable {
                 since,
-                allowed_through_unstable_modules: None,
-            } = stability.level
-        {
-            let stable = match since {
-                StableSince::Version(v) => msrv.meets(cx, v),
-                StableSince::Current => msrv.current(cx).is_none(),
-                StableSince::Err(_) => false,
-            };
-
-            if !stable {
-                return false;
-            }
-        }
+                allowed_through_unstable_modules,
+            } => {
+                let stable = match since {
+                    StableSince::Version(v) => msrv.meets(cx, v),
+                    StableSince::Current => msrv.current(cx).is_none(),
+                    StableSince::Err(_) => false,
+                };
 
-        match cx.tcx.opt_parent(def_id) {
-            Some(parent) => def_id = parent,
-            None => return true,
-        }
-    }
+                if !stable {
+                    Some(false)
+                } else if allowed_through_unstable_modules.is_some() {
+                    // Items marked with #[rustc_allowed_through_unstable_modules = "..."]
+                    // can be short-circuited, since no instability of a parent module
+                    // can override this attribute.
+                    Some(true)
+                } else {
+                    None
+                }
+            },
+        })
+        .unwrap_or(true)
 }

tests/ui/std_instead_of_core.fixed

@@ -96,3 +96,9 @@ fn issue15579() {
 
     let layout = alloc::Layout::new::<u8>();
 }
+
+#[warn(clippy::std_instead_of_core)]
+fn issue13158_core_io() {
+    // items moved from std::io into core::io are stable in an unstable module.
+    type ErrorKindA = std::io::ErrorKind;
+}

tests/ui/std_instead_of_core.rs

@@ -96,3 +96,9 @@ fn issue15579() {
 
     let layout = alloc::Layout::new::<u8>();
 }
+
+#[warn(clippy::std_instead_of_core)]
+fn issue13158_core_io() {
+    // items moved from std::io into core::io are stable in an unstable module.
+    type ErrorKindA = std::io::ErrorKind;
+}