don't evaluate constants if borrowck fails

Author: BoxyUwU

compiler/rustc_middle/src/mir/query.rs

@@ -214,6 +214,7 @@ pub struct BorrowCheckResult<'tcx> {
     pub concrete_opaque_types: VecMap<OpaqueTypeKey<'tcx>, Ty<'tcx>>,
     pub closure_requirements: Option<ClosureRegionRequirements<'tcx>>,
     pub used_mut_upvars: SmallVec<[Field; 8]>,
+    pub errored: bool,
 }
 
 /// The result of the `mir_const_qualif` query.

compiler/rustc_mir/src/borrow_check/mod.rs

@@ -432,10 +432,12 @@ fn do_mir_borrowck<'a, 'tcx>(
         diag.buffer(&mut mbcx.errors_buffer);
     }
 
+    let mut errored = false;
     if !mbcx.errors_buffer.is_empty() {
         mbcx.errors_buffer.sort_by_key(|diag| diag.sort_span);
 
         for diag in mbcx.errors_buffer.drain(..) {
+            errored |= diag.is_error(); 
             mbcx.infcx.tcx.sess.diagnostic().emit_diagnostic(&diag);
         }
     }
@@ -444,6 +446,7 @@ fn do_mir_borrowck<'a, 'tcx>(
         concrete_opaque_types: opaque_type_values,
         closure_requirements: opt_closure_req,
         used_mut_upvars: mbcx.used_mut_upvars,
+        errored,
     };
 
     debug!("do_mir_borrowck: result = {:#?}", result);

compiler/rustc_mir/src/const_eval/eval_queries.rs

@@ -292,6 +292,15 @@ pub fn eval_to_allocation_raw_provider<'tcx>(
         if let Some(error_reported) = tcx.mir_const_qualif_opt_const_arg(def).error_occured {
             return Err(ErrorHandled::Reported(error_reported));
         }
+        
+        let borrowck_results = if let Some(param_did) = def.const_param_did {
+            tcx.mir_borrowck_const_arg((def.did, param_did))
+        } else {
+            tcx.mir_borrowck(def.did)
+        };
+        if borrowck_results.errored {
+            return Err(ErrorHandled::Reported(ErrorReported {}));
+        }
     }
 
     let is_static = tcx.is_static(def.did);

src/test/ui/consts/const-eval/borrowck_error_no_ice.rs

@@ -0,0 +1,9 @@
+struct Bug {
+    A: [(); {
+        let x;
+        x
+        //~^ error: use of possibly-uninitialized variable
+    }],
+}
+
+fn main() {}

src/test/ui/consts/const-eval/borrowck_error_no_ice.stderr

@@ -0,0 +1,9 @@
+error[E0381]: use of possibly-uninitialized variable: `x`
+  --> $DIR/borrowck_error_no_ice.rs:4:9
+   |
+LL |         x
+   |         ^ use of possibly-uninitialized `x`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0381`.

src/test/ui/consts/issue-78655.rs

@@ -1,4 +1,4 @@
-const FOO: *const u32 = { //~ ERROR encountered dangling pointer in final constant
+const FOO: *const u32 = {
     let x;
     &x //~ ERROR borrow of possibly-uninitialized variable: `x`
 };

src/test/ui/consts/issue-78655.stderr

@@ -4,15 +4,6 @@ error[E0381]: borrow of possibly-uninitialized variable: `x`
 LL |     &x
    |     ^^ use of possibly-uninitialized `x`
 
-error: encountered dangling pointer in final constant
-  --> $DIR/issue-78655.rs:1:1
-   |
-LL | / const FOO: *const u32 = {
-LL | |     let x;
-LL | |     &x
-LL | | };
-   | |__^
-
 error: could not evaluate constant pattern
   --> $DIR/issue-78655.rs:7:9
    |
@@ -25,6 +16,6 @@ error: could not evaluate constant pattern
 LL |     let FOO = FOO;
    |         ^^^
 
-error: aborting due to 4 previous errors
+error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0381`.