diff --git a/library/std/src/sys_common/thread_local_key.rs b/library/std/src/sys_common/thread_local_key.rs
index 7dcc114109958..a9cd26389cd41 100644
--- a/library/std/src/sys_common/thread_local_key.rs
+++ b/library/std/src/sys_common/thread_local_key.rs
@@ -1,4 +1,4 @@
-//! OS-based thread local storage
+//! OS-based thread local storage for non-Windows systems
 //!
 //! This module provides an implementation of OS-based thread local storage,
 //! using the native OS-provided facilities (think `TlsAlloc` or
@@ -11,6 +11,9 @@
 //! the OS-TLS key. The other is a type which does implement `Drop` and hence
 //! has a safe interface.
 //!
+//! Windows doesn't use this module at all; `sys::pal::windows::thread_local_key`
+//! gets imported in its stead.
+//!
 //! # Usage
 //!
 //! This module should likely not be used directly unless other primitives are
diff --git a/src/librustdoc/clean/types.rs b/src/librustdoc/clean/types.rs
index b34d54fd9c82c..393996cc770f0 100644
--- a/src/librustdoc/clean/types.rs
+++ b/src/librustdoc/clean/types.rs
@@ -23,6 +23,7 @@ use rustc_hir::{BodyId, Mutability};
 use rustc_hir_analysis::check::intrinsic::intrinsic_operation_unsafety;
 use rustc_index::IndexVec;
 use rustc_metadata::rendered_const;
+use rustc_middle::span_bug;
 use rustc_middle::ty::fast_reject::SimplifiedType;
 use rustc_middle::ty::{self, TyCtxt, Visibility};
 use rustc_resolve::rustdoc::{
@@ -266,8 +267,15 @@ impl ExternalCrate {
         let as_primitive = |res: Res<!>| {
             let Res::Def(DefKind::Mod, def_id) = res else { return None };
             tcx.get_attrs(def_id, sym::rustc_doc_primitive).find_map(|attr| {
-                // FIXME: should warn on unknown primitives?
-                Some((def_id, PrimitiveType::from_symbol(attr.value_str()?)?))
+                let attr_value = attr.value_str().expect("syntax should already be validated");
+                let Some(prim) = PrimitiveType::from_symbol(attr_value) else {
+                    span_bug!(
+                        attr.span,
+                        "primitive `{attr_value}` is not a member of `PrimitiveType`"
+                    );
+                };
+
+                Some((def_id, prim))
             })
         };