Add UnexpectedUnsized variant to LayoutError

Signed-off-by: FedericoBruzzone <federico.bruzzone.i@gmail.com>

Author: FedericoBruzzone

compiler/rustc_hir_analysis/src/hir_ty_lowering/cmse.rs

@@ -211,7 +211,11 @@ fn should_emit_generic_error<'tcx>(abi: ExternAbi, layout_err: &'tcx LayoutError
                 _ => bug!("invalid ABI: {abi}"),
             }
         }
-        SizeOverflow(..) | NormalizationFailure(..) | ReferencesError(..) | Cycle(..) => {
+        UnexpectedUnsized(..)
+        | SizeOverflow(..)
+        | NormalizationFailure(..)
+        | ReferencesError(..)
+        | Cycle(..) => {
             false // not our job to report these
         }
     }

compiler/rustc_middle/messages.ftl

@@ -108,3 +108,6 @@ middle_unknown_layout =
 middle_values_too_big =
     values of the type `{$ty}` are too big for the target architecture
 middle_written_to_path = the full type name has been written to '{$path}'
+
+middle_unexpected_unsized =
+    cannot determine the layout of the type `{$ty}`

compiler/rustc_middle/src/error.rs

@@ -129,6 +129,9 @@ pub enum LayoutError<'tcx> {
     #[diag(middle_unknown_layout)]
     Unknown { ty: Ty<'tcx> },
 
+    #[diag(middle_unexpected_unsized)]
+    Unsized { ty: Ty<'tcx> },
+
     #[diag(middle_values_too_big)]
     Overflow { ty: Ty<'tcx> },
 

compiler/rustc_middle/src/ty/layout.rs

@@ -231,6 +231,7 @@ impl fmt::Display for ValidityRequirement {
 pub enum LayoutError<'tcx> {
     Unknown(Ty<'tcx>),
     SizeOverflow(Ty<'tcx>),
+    UnexpectedUnsized(Ty<'tcx>),
     NormalizationFailure(Ty<'tcx>, NormalizationError<'tcx>),
     ReferencesError(ErrorGuaranteed),
     Cycle(ErrorGuaranteed),
@@ -244,6 +245,7 @@ impl<'tcx> LayoutError<'tcx> {
         match self {
             Unknown(_) => middle_unknown_layout,
             SizeOverflow(_) => middle_values_too_big,
+            UnexpectedUnsized(_) => middle_unexpected_unsized,
             NormalizationFailure(_, _) => middle_cannot_be_normalized,
             Cycle(_) => middle_cycle,
             ReferencesError(_) => middle_layout_references_error,
@@ -257,6 +259,7 @@ impl<'tcx> LayoutError<'tcx> {
         match self {
             Unknown(ty) => E::Unknown { ty },
             SizeOverflow(ty) => E::Overflow { ty },
+            UnexpectedUnsized(ty) => E::Unsized { ty },
             NormalizationFailure(ty, e) => {
                 E::NormalizationFailure { ty, failure_ty: e.get_type_for_failure() }
             }
@@ -272,6 +275,9 @@ impl<'tcx> fmt::Display for LayoutError<'tcx> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match *self {
             LayoutError::Unknown(ty) => write!(f, "the type `{ty}` has an unknown layout"),
+            LayoutError::UnexpectedUnsized(ty) => {
+                write!(f, "cannot determine the layout for the type `{ty}`")
+            }
             LayoutError::SizeOverflow(ty) => {
                 write!(f, "values of the type `{ty}` are too big for the target architecture")
             }
@@ -355,6 +361,7 @@ impl<'tcx> SizeSkeleton<'tcx> {
             Err(
                 e @ LayoutError::Cycle(_)
                 | e @ LayoutError::SizeOverflow(_)
+                | e @ LayoutError::UnexpectedUnsized(_)
                 | e @ LayoutError::NormalizationFailure(..)
                 | e @ LayoutError::ReferencesError(_),
             ) => return Err(e),

compiler/rustc_transmute/src/layout/tree.rs

@@ -197,6 +197,7 @@ pub(crate) mod rustc {
             match err {
                 LayoutError::Unknown(..)
                 | LayoutError::ReferencesError(..)
+                | LayoutError::UnexpectedUnsized(..)
                 | LayoutError::NormalizationFailure(..) => Self::UnknownLayout,
                 LayoutError::SizeOverflow(..) => Self::SizeOverflow,
                 LayoutError::Cycle(err) => Self::TypeError(*err),

src/librustdoc/html/templates/type_layout.html

@@ -44,6 +44,14 @@ <h2 id="layout" class="section-header"> {# #}
             <strong>Note:</strong> Encountered an error during type layout; {#+ #}
             the type was too big. {# #}
         </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
+        user know that we couldn't compute the layout. #}
+        {% when Err(LayoutError::UnexpectedUnsized(_)) %}
+        <p> {# #}
+            <strong>Note:</strong> Encountered an error during type layout; {#+ #}
+            the type was unexpectedly unsized. {# #}
+        </p>
         {% when Err(LayoutError::ReferencesError(_)) %}
         <p> {# #}
             <strong>Note:</strong> Encountered an error during type layout; {#+ #}