fix: alloc_instead_of_core FP when alloc is an alias

Author: profetia

clippy_lints/src/std_instead_of_core.rs

@@ -137,6 +137,13 @@ impl<'tcx> LateLintPass<'tcx> for StdReexports {
                     },
                 },
                 sym::alloc => {
+                    if let Res::Def(DefKind::Mod, crate_def_id) = first_segment.res
+                        && let crate_name = cx.tcx.crate_name(crate_def_id.krate)
+                        && crate_name != first_segment.ident.name
+                    {
+                        return;
+                    }
+
                     if cx.tcx.crate_name(def_id.krate) == sym::core {
                         (ALLOC_INSTEAD_OF_CORE, "alloc", "core")
                     } else {

tests/ui/std_instead_of_core.fixed

@@ -89,3 +89,10 @@ fn msrv_1_76(_: std::net::IpAddr) {}
 #[clippy::msrv = "1.77"]
 fn msrv_1_77(_: core::net::IpAddr) {}
 //~^ std_instead_of_core
+
+#[warn(clippy::alloc_instead_of_core)]
+fn issue15579() {
+    use std::alloc;
+
+    let layout = alloc::Layout::new::<u8>();
+}

tests/ui/std_instead_of_core.rs

@@ -89,3 +89,10 @@ fn msrv_1_76(_: std::net::IpAddr) {}
 #[clippy::msrv = "1.77"]
 fn msrv_1_77(_: std::net::IpAddr) {}
 //~^ std_instead_of_core
+
+#[warn(clippy::alloc_instead_of_core)]
+fn issue15579() {
+    use std::alloc;
+
+    let layout = alloc::Layout::new::<u8>();
+}