Auto merge of #61498 - TankhouseAle:const-fn-type-name, r=oli-obk

Add "type_name" support in emulate_intrinsic()

I did some dumb Git things and deleted my original fork repo semi-accidentally (but probably for the best as I'd messed up the history.)

This is the same issue as #61399, which was obviously auto-closed, to be clear.

src/librustc_mir/interpret/intrinsics.rs

@@ -11,7 +11,7 @@ use rustc::mir::interpret::{
 };
 
 use super::{
- Machine, PlaceTy, OpTy, InterpretCx,
+ Machine, PlaceTy, OpTy, InterpretCx, Immediate,
 };
 
 mod type_name;
@@ -78,6 +78,16 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> InterpretCx<'a, 'mir, 'tcx, M>
  let id_val = Scalar::from_uint(type_id, dest.layout.size);
  self.write_scalar(id_val, dest)?;
  }
+
+ "type_name" => {
+ let alloc = alloc_type_name(self.tcx.tcx, substs.type_at(0));
+ let name_id = self.tcx.alloc_map.lock().create_memory_alloc(alloc);
+ let id_ptr = self.memory.tag_static_base_pointer(name_id.into());
+ let alloc_len = alloc.bytes.len() as u64;
+ let name_val = Immediate::new_slice(Scalar::Ptr(id_ptr), alloc_len, self);
+ self.write_immediate(name_val, dest)?;
+ }
+
  | "ctpop"
  | "cttz"
  | "cttz_nonzero"

src/librustc_mir/interpret/intrinsics/type_name.rs

@@ -213,16 +213,23 @@ impl Write for AbsolutePathPrinter<'_, '_> {
 /// Produces an absolute path representation of the given type. See also the documentation on
 /// `std::any::type_name`
 pub fn type_name<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, ty: Ty<'tcx>) -> &'tcx ty::Const<'tcx> {
- let path = AbsolutePathPrinter { tcx, path: String::new() }.print_type(ty).unwrap().path;
- let len = path.len();
- let alloc = Allocation::from_byte_aligned_bytes(path.into_bytes());
- let alloc = tcx.intern_const_alloc(alloc);
+ let alloc = alloc_type_name(tcx, ty);
  tcx.mk_const(ty::Const {
  val: ConstValue::Slice {
  data: alloc,
  start: 0,
- end: len,
+ end: alloc.bytes.len(),
  },
  ty: tcx.mk_static_str(),
  })
 }
+
+/// Directly returns an `Allocation` containing an absolute path representation of the given type.
+pub(super) fn alloc_type_name<'a, 'tcx>(
+ tcx: TyCtxt<'a, 'tcx, 'tcx>,
+ ty: Ty<'tcx>
+) -> &'tcx Allocation {
+ let path = AbsolutePathPrinter { tcx, path: String::new() }.print_type(ty).unwrap().path;
+ let alloc = Allocation::from_byte_aligned_bytes(path.into_bytes());
+ tcx.intern_const_alloc(alloc)
+}

src/test/run-pass/ctfe/const-fn-type-name.rs

@@ -0,0 +1,37 @@
+// run-pass
+
+#![feature(core_intrinsics)]
+#![feature(const_fn)]
+#![allow(dead_code)]
+
+const fn type_name_wrapper<T>(_: &T) -> &'static str {
+ unsafe { core::intrinsics::type_name::<T>() }
+}
+
+struct Struct<TA, TB, TC> {
+ a: TA,
+ b: TB,
+ c: TC,
+}
+
+type StructInstantiation = Struct<i8, f64, bool>;
+
+const CONST_STRUCT: StructInstantiation = StructInstantiation {
+ a: 12,
+ b: 13.7,
+ c: false,
+};
+
+const CONST_STRUCT_NAME: &'static str = type_name_wrapper(&CONST_STRUCT);
+
+fn main() {
+ let non_const_struct = StructInstantiation {
+ a: 87,
+ b: 65.99,
+ c: true,
+ };
+
+ let non_const_struct_name = type_name_wrapper(&non_const_struct);
+
+ assert_eq!(CONST_STRUCT_NAME, non_const_struct_name);
+}