Auto merge of #119000 - celinval:smir-cstr, r=ouz-a

Add a method to StableMIR to check if a type is a CStr

Also add a check that StableMIR works properly with C string literal.

compiler/rustc_smir/src/rustc_smir/context.rs

@@ -219,6 +219,12 @@ impl<'tcx> Context for TablesWrapper<'tcx> {
         def.internal(&mut *tables).repr().simd()
     }
 
+    fn adt_is_cstr(&self, def: AdtDef) -> bool {
+        let mut tables = self.0.borrow_mut();
+        let def_id = def.0.internal(&mut *tables);
+        tables.tcx.lang_items().c_str() == Some(def_id)
+    }
+
     fn fn_sig(&self, def: FnDef, args: &GenericArgs) -> PolyFnSig {
         let mut tables = self.0.borrow_mut();
         let def_id = def.0.internal(&mut *tables);

compiler/stable_mir/src/compiler_interface.rs

@@ -72,6 +72,9 @@ pub trait Context {
     /// Returns whether this ADT is simd.
     fn adt_is_simd(&self, def: AdtDef) -> bool;
 
+    /// Returns whether this definition is a C string.
+    fn adt_is_cstr(&self, def: AdtDef) -> bool;
+
     /// Retrieve the function signature for the given generic arguments.
     fn fn_sig(&self, def: FnDef, args: &GenericArgs) -> PolyFnSig;
 

compiler/stable_mir/src/ty.rs

@@ -316,6 +316,12 @@ impl TyKind {
         *self == TyKind::RigidTy(RigidTy::Str)
     }
 
+    #[inline]
+    pub fn is_cstr(&self) -> bool {
+        let TyKind::RigidTy(RigidTy::Adt(def, _)) = self else { return false };
+        with(|cx| cx.adt_is_cstr(*def))
+    }
+
     #[inline]
     pub fn is_slice(&self) -> bool {
         matches!(self, TyKind::RigidTy(RigidTy::Slice(_)))