Change control flow error to delay span bug

Author: ecstatic-morse

src/librustc_mir/transform/check_consts/validation.rs

@@ -461,7 +461,14 @@ impl Visitor<'tcx> for Validator<'_, 'mir, 'tcx> {
                 self.super_statement(statement, location);
             }
             StatementKind::FakeRead(FakeReadCause::ForMatchedPlace, _) => {
-                self.check_op(ops::IfOrMatch);
+                // FIXME: make this the `emit_error` impl of `ops::IfOrMatch` once the const
+                // checker is no longer run in compatability mode.
+                if !self.tcx.sess.opts.debugging_opts.unleash_the_miri_inside_of_you {
+                    self.tcx.sess.delay_span_bug(
+                        self.span,
+                        "complex control flow is forbidden in a const context",
+                    );
+                }
             }
             // FIXME(eddyb) should these really do nothing?
             StatementKind::FakeRead(..) |

src/librustc_mir/transform/qualify_consts.rs

@@ -723,8 +723,12 @@ impl<'a, 'tcx> Checker<'a, 'tcx> {
                     bb = target;
                 }
                 _ => {
-                    self.not_const(ops::Loop);
-                    validator.check_op(ops::Loop);
+                    if !self.tcx.sess.opts.debugging_opts.unleash_the_miri_inside_of_you {
+                        self.tcx.sess.delay_span_bug(
+                            self.span,
+                            "complex control flow is forbidden in a const context",
+                        );
+                    }
                     break;
                 }
             }
@@ -1253,7 +1257,12 @@ impl<'a, 'tcx> Visitor<'tcx> for Checker<'a, 'tcx> {
                 self.super_statement(statement, location);
             }
             StatementKind::FakeRead(FakeReadCause::ForMatchedPlace, _) => {
-                self.not_const(ops::IfOrMatch);
+                if !self.tcx.sess.opts.debugging_opts.unleash_the_miri_inside_of_you {
+                    self.tcx.sess.delay_span_bug(
+                        self.span,
+                        "complex control flow is forbidden in a const context",
+                    );
+                }
             }
             // FIXME(eddyb) should these really do nothing?
             StatementKind::FakeRead(..) |

src/librustc_passes/check_const.rs

@@ -60,10 +60,6 @@ impl fmt::Display for ConstKind {
 }
 
 fn check_mod_const_bodies(tcx: TyCtxt<'_>, module_def_id: DefId) {
-    if tcx.sess.opts.debugging_opts.unleash_the_miri_inside_of_you {
-        return;
-    }
-
     let mut vis = CheckConstVisitor::new(tcx);
     tcx.hir().visit_item_likes_in_module(module_def_id, &mut vis.as_deep_visitor());
 }
@@ -93,6 +89,11 @@ impl<'tcx> CheckConstVisitor<'tcx> {
 
     /// Emits an error when an unsupported expression is found in a const context.
     fn const_check_violated(&self, bad_op: &str, span: Span) {
+        if self.sess.opts.debugging_opts.unleash_the_miri_inside_of_you {
+            self.sess.span_warn(span, "skipping const checks");
+            return;
+        }
+
         let const_kind = self.const_kind
             .expect("`const_check_violated` may only be called inside a const context");