Make std::mem::needs_drop a const fn rust-lang#51929

JoshBrudnak · Aug 25, 2018 · d06266f · d06266f
1 parent af2be23
commit d06266f
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Showing 2 changed files with 11 additions and 0 deletions.
diff --git a/src/librustc_mir/interpret/const_eval.rs b/src/librustc_mir/interpret/const_eval.rs
@@ -359,6 +359,16 @@ impl<'mir, 'tcx> super::Machine<'mir, 'tcx> for CompileTimeEvaluator {
                 ecx.write_scalar(size_val, dest)?;
             }
 
+            "needs_drop" => {
+                let ty = substs.type_at(0);
+                let size = ecx.layout_of(ty)?.size.bytes() as u128;
+                let size_val = Scalar::Bits {
+                    bits: size,
+                    size: dest.layout.size.bytes() as u8,
+                };
+                ecx.write_scalar(size_val, dest)?;
+            }
+
             "type_id" => {
                 let ty = substs.type_at(0);
                 let type_id = ecx.tcx.type_id_hash(ty) as u128;

diff --git a/src/librustc_mir/transform/qualify_consts.rs b/src/librustc_mir/transform/qualify_consts.rs
@@ -823,6 +823,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Qualifier<'a, 'tcx, 'tcx> {
                         match &self.tcx.item_name(def_id).as_str()[..] {
                             | "size_of"
                             | "min_align_of"
+                            | "needs_drop"
                             | "type_id"
                             | "bswap"
                             | "ctpop"