Add `TooGeneric` variant to `LayoutError` and emit `Unknown` one

- `check-pass` test for a MRE of #135020
- fail test for #135138
- switch to `TooGeneric` for checking CMSE fn signatures
- switch to `TooGeneric` for compute `SizeSkeleton` (for transmute)
- fix broken tests

1 files changed, 11 insertions, 5 deletions

diff --git a/src/librustdoc/html/templates/type_layout.html b/src/librustdoc/html/templates/type_layout.html
index aee96fb8c41..9c62826ccc2 100644
--- a/src/librustdoc/html/templates/type_layout.html
+++ b/src/librustdoc/html/templates/type_layout.html
@@ -28,13 +28,11 @@
         {% endfor %}
     </ul>
     {% endif %}
-    {# This kind of layout error can occur with valid code, e.g. if you try to
-    get the layout of a generic type such as `Vec<T>`. #}
+        {# This kind of layout error can occur with valid code, for example
+        if there are trivial bounds: `struct Foo(str, str) where str: Sized;`. #}
         {% when Err(LayoutError::Unknown(_)) %}
         <p> {# #}
-            <strong>Note:</strong> Unable to compute type layout, {#+ #}
-            possibly due to this type having generic parameters. {#+ #}
-            Layout can only be computed for concrete, fully-instantiated types. {# #}
+            <strong>Note:</strong> Unable to compute type layout. {# #}
         </p>
         {# This kind of error probably can't happen with valid code, but we don't
         want to panic and prevent the docs from building, so we just let the
@@ -44,6 +42,14 @@
             <strong>Note:</strong> Encountered an error during type layout; {#+ #}
             the type was too big. {# #}
         </p>
+        {# This kind of layout error can occur with valid code, e.g. if you try to
+        get the layout of a generic type such as `Vec<T>`. #}
+        {% when Err(LayoutError::TooGeneric(_)) %}
+        <p> {# #}
+            <strong>Note:</strong> Unable to compute type layout, {#+ #}
+            possibly due to this type having generic parameters. {#+ #}
+            Layout can only be computed for concrete, fully-instantiated types. {# #}
+        </p>
         {% when Err(LayoutError::ReferencesError(_)) %}
         <p> {# #}
             <strong>Note:</strong> Encountered an error during type layout; {#+ #}