more robust method checking through DefId and diagnostic_item

Author: RalfJung

src/libcore/mem/maybe_uninit.rs

@@ -440,6 +440,7 @@ impl<T> MaybeUninit<T> {
     /// ```
     #[stable(feature = "maybe_uninit", since = "1.36.0")]
     #[inline(always)]
+    #[cfg_attr(all(not(bootstrap)), rustc_diagnostic_item = "assume_init")]
     pub unsafe fn assume_init(self) -> T {
         intrinsics::panic_if_uninhabited::<T>();
         ManuallyDrop::into_inner(self.value)

src/librustc_lint/builtin.rs

@@ -1933,9 +1933,10 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidValue {
                         }
                     }
                 }
-            } else if let hir::ExprKind::MethodCall(ref path, _, ref args) = expr.kind {
+            } else if let hir::ExprKind::MethodCall(_, _, ref args) = expr.kind {
                 // Find problematic calls to `MaybeUninit::assume_init`.
-                if path.ident.name == sym::assume_init {
+                let def_id = cx.tables.type_dependent_def_id(expr.hir_id)?;
+                if cx.tcx.is_diagnostic_item(sym::assume_init, def_id) {
                     // This is a call to *some* method named `assume_init`.
                     // See if the `self` parameter is one of the dangerous constructors.
                     if let hir::ExprKind::Call(ref path_expr, _) = args[0].kind {