Rollup merge of rust-lang#115908 - cjgillot:lint-noclone, r=oli-obk

Do not clone MIR for const-prop lint.

Addresses rust-lang#115797 (comment)

Author: matthiaskrgr

compiler/rustc_mir_transform/src/const_prop_lint.rs

@@ -105,25 +105,12 @@ impl<'tcx> MirLint<'tcx> for ConstProp {
 
         trace!("ConstProp starting for {:?}", def_id);
 
-        let dummy_body = &Body::new(
-            body.source,
-            (*body.basic_blocks).to_owned(),
-            body.source_scopes.clone(),
-            body.local_decls.clone(),
-            Default::default(),
-            body.arg_count,
-            Default::default(),
-            body.span,
-            body.generator_kind(),
-            body.tainted_by_errors,
-        );
-
         // FIXME(oli-obk, eddyb) Optimize locals (or even local paths) to hold
         // constants, instead of just checking for const-folding succeeding.
         // That would require a uniform one-def no-mutation analysis
         // and RPO (or recursing when needing the value of a local).
-        let mut optimization_finder = ConstPropagator::new(body, dummy_body, tcx);
-        optimization_finder.visit_body(body);
+        let mut linter = ConstPropagator::new(body, tcx);
+        linter.visit_body(body);
 
         trace!("ConstProp done for {:?}", def_id);
     }
@@ -169,11 +156,7 @@ impl<'tcx> ty::layout::HasParamEnv<'tcx> for ConstPropagator<'_, 'tcx> {
 }
 
 impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
-    fn new(
-        body: &Body<'tcx>,
-        dummy_body: &'mir Body<'tcx>,
-        tcx: TyCtxt<'tcx>,
-    ) -> ConstPropagator<'mir, 'tcx> {
+    fn new(body: &'mir Body<'tcx>, tcx: TyCtxt<'tcx>) -> ConstPropagator<'mir, 'tcx> {
         let def_id = body.source.def_id();
         let args = &GenericArgs::identity_for_item(tcx, def_id);
         let param_env = tcx.param_env_reveal_all_normalized(def_id);
@@ -204,7 +187,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
 
         ecx.push_stack_frame(
             Instance::new(def_id, args),
-            dummy_body,
+            body,
             &ret,
             StackPopCleanup::Root { cleanup: false },
         )