don't point at const usage site for resolution-time errors

also share the code that emits the actual error

src/base.rs

@@ -2,7 +2,6 @@
 
 use rustc_ast::InlineAsmOptions;
 use rustc_index::IndexVec;
-use rustc_middle::mir::interpret::ErrorHandled;
 use rustc_middle::ty::adjustment::PointerCoercion;
 use rustc_middle::ty::layout::FnAbiOf;
 use rustc_middle::ty::print::with_no_trimmed_paths;
@@ -251,21 +250,15 @@ pub(crate) fn verify_func(
 }
 
 fn codegen_fn_body(fx: &mut FunctionCx<'_, '_, '_>, start_block: Block) {
-    match fx.mir.post_mono_checks(fx.tcx, ty::ParamEnv::reveal_all(), |c| Ok(fx.monomorphize(c))) {
-        Ok(()) => {}
-        Err(ErrorHandled::TooGeneric(span)) => {
-            span_bug!(span, "codegen encountered polymorphic constant");
-        }
-        Err(ErrorHandled::Reported(info, span)) => {
-            if !info.is_tainted_by_errors() {
-                fx.tcx.sess.span_err(span, "erroneous constant encountered");
-            }
-            fx.bcx.append_block_params_for_function_params(fx.block_map[START_BLOCK]);
-            fx.bcx.switch_to_block(fx.block_map[START_BLOCK]);
-            // compilation should have been aborted
-            fx.bcx.ins().trap(TrapCode::UnreachableCodeReached);
-            return;
-        }
+    if let Err(err) =
+        fx.mir.post_mono_checks(fx.tcx, ty::ParamEnv::reveal_all(), |c| Ok(fx.monomorphize(c)))
+    {
+        err.emit_err(fx.tcx);
+        fx.bcx.append_block_params_for_function_params(fx.block_map[START_BLOCK]);
+        fx.bcx.switch_to_block(fx.block_map[START_BLOCK]);
+        // compilation should have been aborted
+        fx.bcx.ins().trap(TrapCode::UnreachableCodeReached);
+        return;
     }
 
     let arg_uninhabited = fx