Auto merge of rust-lang#114459 - cjgillot:simplify-ctfe, r=oli-obk

Do not run ConstProp on mir_for_ctfe.

This pass does not seem to be useful any more. The const-prop lints are now run by `tcx.mir_drops_elaborated_and_const_checked`, and the const-prop opt should never emit any diagnostic.

Author: bors

compiler/rustc_mir_transform/src/lib.rs

@@ -338,38 +338,9 @@ fn inner_mir_for_ctfe(tcx: TyCtxt<'_>, def: LocalDefId) -> Body<'_> {
         return shim::build_adt_ctor(tcx, def.to_def_id());
     }
 
-    let context = tcx
-        .hir()
-        .body_const_context(def)
-        .expect("mir_for_ctfe should not be used for runtime functions");
-
     let body = tcx.mir_drops_elaborated_and_const_checked(def).borrow().clone();
 
     let mut body = remap_mir_for_const_eval_select(tcx, body, hir::Constness::Const);
-
-    match context {
-        // Do not const prop functions, either they get executed at runtime or exported to metadata,
-        // so we run const prop on them, or they don't, in which case we const evaluate some control
-        // flow paths of the function and any errors in those paths will get emitted as const eval
-        // errors.
-        hir::ConstContext::ConstFn => {}
-        // Static items always get evaluated, so we can just let const eval see if any erroneous
-        // control flow paths get executed.
-        hir::ConstContext::Static(_) => {}
-        // Associated constants get const prop run so we detect common failure situations in the
-        // crate that defined the constant.
-        // Technically we want to not run on regular const items, but oli-obk doesn't know how to
-        // conveniently detect that at this point without looking at the HIR.
-        hir::ConstContext::Const => {
-            pm::run_passes(
-                tcx,
-                &mut body,
-                &[&const_prop::ConstProp],
-                Some(MirPhase::Runtime(RuntimePhase::Optimized)),
-            );
-        }
-    }
-
     pm::run_passes(tcx, &mut body, &[&ctfe_limit::CtfeLimit], None);
 
     body