Do not run AST borrowck when -Zborrowck=mir

src/librustc/ty/context.rs

@@ -1354,6 +1354,12 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         !self.sess.opts.debugging_opts.disable_ast_check_for_mutation_in_guard
     }
 
+    /// If true, we should use the AST-based borrowck (we may *also* use
+    /// the MIR-based borrowck).
+    pub fn use_ast_borrowck(self) -> bool {
+        self.borrowck_mode().use_ast()
+    }
+
     /// If true, we should use the MIR-based borrowck (we may *also* use
     /// the AST-based borrowck).
     pub fn use_mir_borrowck(self) -> bool {

src/librustc_borrowck/borrowck/mod.rs

@@ -89,6 +89,8 @@ pub struct AnalysisData<'a, 'tcx: 'a> {
 fn borrowck<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, owner_def_id: DefId)
     -> Lrc<BorrowCheckResult>
 {
+    assert!(tcx.use_ast_borrowck());
+
     debug!("borrowck(body_owner_def_id={:?})", owner_def_id);
 
     let owner_id = tcx.hir.as_local_node_id(owner_def_id).unwrap();

src/librustc_driver/driver.rs

@@ -1279,7 +1279,11 @@ where
                 middle::liveness::check_crate(tcx)
             });
 
-            time(sess, "borrow checking", || borrowck::check_crate(tcx));
+            time(sess, "borrow checking", || {
+                if tcx.use_ast_borrowck() {
+                    borrowck::check_crate(tcx);
+                }
+            });
 
             time(sess,
                  "MIR borrow checking",

src/librustc_mir/transform/mod.rs

@@ -225,7 +225,10 @@ fn optimized_mir<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) -> &'tcx
     // (Mir-)Borrowck uses `mir_validated`, so we have to force it to
     // execute before we can steal.
     let _ = tcx.mir_borrowck(def_id);
-    let _ = tcx.borrowck(def_id);
+
+    if tcx.use_ast_borrowck() {
+        let _ = tcx.borrowck(def_id);
+    }
 
     let mut mir = tcx.mir_validated(def_id).steal();
     run_passes![tcx, mir, def_id, 2;

src/test/ui/error-codes/E0017.nll.stderr

@@ -10,18 +10,18 @@ error[E0017]: references in statics may only refer to immutable values
 LL | static STATIC_REF: &'static mut i32 = &mut X; //~ ERROR E0017
    |                                       ^^^^^^ statics require immutable values
 
-error[E0017]: references in statics may only refer to immutable values
-  --> $DIR/E0017.rs:17:38
-   |
-LL | static CONST_REF: &'static mut i32 = &mut C; //~ ERROR E0017
-   |                                      ^^^^^^ statics require immutable values
-
 error[E0596]: cannot borrow immutable item `X` as mutable
   --> $DIR/E0017.rs:15:39
    |
 LL | static STATIC_REF: &'static mut i32 = &mut X; //~ ERROR E0017
    |                                       ^^^^^^ cannot borrow as mutable
 
+error[E0017]: references in statics may only refer to immutable values
+  --> $DIR/E0017.rs:17:38
+   |
+LL | static CONST_REF: &'static mut i32 = &mut C; //~ ERROR E0017
+   |                                      ^^^^^^ statics require immutable values
+
 error: aborting due to 4 previous errors
 
 Some errors occurred: E0017, E0596.

src/test/ui/error-codes/E0388.nll.stderr

@@ -10,18 +10,18 @@ error[E0017]: references in statics may only refer to immutable values
 LL | static STATIC_REF: &'static mut i32 = &mut X; //~ ERROR E0017
    |                                       ^^^^^^ statics require immutable values
 
-error[E0017]: references in statics may only refer to immutable values
-  --> $DIR/E0388.rs:17:38
-   |
-LL | static CONST_REF: &'static mut i32 = &mut C; //~ ERROR E0017
-   |                                      ^^^^^^ statics require immutable values
-
 error[E0596]: cannot borrow immutable item `X` as mutable
   --> $DIR/E0388.rs:15:39
    |
 LL | static STATIC_REF: &'static mut i32 = &mut X; //~ ERROR E0017
    |                                       ^^^^^^ cannot borrow as mutable
 
+error[E0017]: references in statics may only refer to immutable values
+  --> $DIR/E0388.rs:17:38
+   |
+LL | static CONST_REF: &'static mut i32 = &mut C; //~ ERROR E0017
+   |                                      ^^^^^^ statics require immutable values
+
 error: aborting due to 4 previous errors
 
 Some errors occurred: E0017, E0596.