Begin generating semantic reprs for records

crates/compiler/mono/src/layout/semantic.rs

@@ -0,0 +1,24 @@
+//! Semantic representations of memory layouts for the purposes of specialization.
+
+/// A semantic representation of a memory layout.
+/// Semantic representations describe the shape of a type a [Layout][super::Layout] is generated
+/// for. Semantic representations disambiguate types that have the same runtime memory layout, but
+/// different shapes.
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
+pub enum SemanticRepr<'a> {
+    None,
+    Record(SemaRecord<'a>),
+}
+
+impl<'a> SemanticRepr<'a> {
+    pub(super) const EMPTY_RECORD: Self = Self::Record(SemaRecord { fields: &[] });
+
+    pub(super) fn record(fields: &'a [&'a str]) -> Self {
+        Self::Record(SemaRecord { fields })
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
+pub struct SemaRecord<'a> {
+    pub fields: &'a [&'a str],
+}