Evaluate all mir.required_consts and report any errors

Fixes #981

Author: bjorn3

src/base.rs

@@ -157,6 +157,8 @@ pub(crate) fn verify_func(tcx: TyCtxt<'_>, writer: &crate::pretty_clif::CommentW
 }
 
 fn codegen_fn_content(fx: &mut FunctionCx<'_, '_, impl Backend>) {
+    crate::constant::check_constants(fx);
+
     for (bb, bb_data) in fx.mir.basic_blocks().iter_enumerated() {
         let block = fx.get_block(bb);
         fx.bcx.switch_to_block(block);

src/constant.rs

@@ -1,8 +1,9 @@
 use rustc_span::DUMMY_SP;
 
+use rustc_errors::ErrorReported;
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use rustc_middle::mir::interpret::{
-    read_target_uint, AllocId, Allocation, ConstValue, GlobalAlloc, Pointer, Scalar,
+    read_target_uint, AllocId, Allocation, ConstValue, ErrorHandled, GlobalAlloc, Pointer, Scalar,
 };
 use rustc_middle::ty::{Const, ConstKind};
 use rustc_target::abi::Align;
@@ -34,6 +35,29 @@ impl ConstantCx {
     }
 }
 
+pub(crate) fn check_constants(fx: &mut FunctionCx<'_, '_, impl Backend>) {
+    for constant in &fx.mir.required_consts {
+        let const_ = fx.monomorphize(&constant.literal);
+        match const_.val {
+            ConstKind::Value(_) => {}
+            ConstKind::Unevaluated(def, ref substs, promoted) => {
+                if let Err(err) = fx.tcx.const_eval_resolve(ParamEnv::reveal_all(), def, substs, promoted, None) {
+                    match err {
+                        ErrorHandled::Reported(ErrorReported) | ErrorHandled::Linted => {
+                            fx.tcx.sess.span_err(constant.span, "erroneous constant encountered");
+                        }
+                        ErrorHandled::TooGeneric => {
+                            span_bug!(constant.span, "codgen encountered polymorphic constant: {:?}", err);
+                        }
+                    }
+                }
+            }
+            ConstKind::Param(_) | ConstKind::Infer(_) | ConstKind::Bound(_, _)
+            | ConstKind::Placeholder(_) | ConstKind::Error(_) => unreachable!("{:?}", const_),
+        }
+    }
+}
+
 pub(crate) fn codegen_static(constants_cx: &mut ConstantCx, def_id: DefId) {
     constants_cx.todo.push(TodoItem::Static(def_id));
 }

src/lib.rs

@@ -5,6 +5,7 @@
 extern crate flate2;
 #[cfg(feature = "jit")]
 extern crate libc;
+#[macro_use]
 extern crate rustc_middle;
 extern crate rustc_codegen_ssa;
 extern crate rustc_data_structures;