make intern_const_alloc_recursive return error fix #78655

Author: vn-ki

compiler/rustc_middle/src/mir/interpret/error.rs

@@ -81,6 +81,12 @@ impl From<ErrorHandled> for InterpErrorInfo<'_> {
     }
 }
 
+impl From<ErrorReported> for InterpErrorInfo<'_> {
+    fn from(err: ErrorReported) -> Self {
+        InterpError::InvalidProgram(InvalidProgramInfo::AlreadyReported(err)).into()
+    }
+}
+
 impl<'tcx> From<InterpError<'tcx>> for InterpErrorInfo<'tcx> {
     fn from(kind: InterpError<'tcx>) -> Self {
         let capture_backtrace = tls::with_opt(|tcx| {
@@ -115,8 +121,8 @@ pub enum InvalidProgramInfo<'tcx> {
     /// Cannot compute this constant because it depends on another one
     /// which already produced an error.
     ReferencedConstant,
-    /// Abort in case type errors are reached.
-    TypeckError(ErrorReported),
+    /// Abort in case errors are already reported.
+    AlreadyReported(ErrorReported),
     /// An error occurred during layout computation.
     Layout(layout::LayoutError<'tcx>),
     /// An invalid transmute happened.
@@ -129,7 +135,7 @@ impl fmt::Display for InvalidProgramInfo<'_> {
         match self {
             TooGeneric => write!(f, "encountered overly generic constant"),
             ReferencedConstant => write!(f, "referenced constant has errors"),
-            TypeckError(ErrorReported) => {
+            AlreadyReported(ErrorReported) => {
                 write!(f, "encountered constants with type errors, stopping evaluation")
             }
             Layout(ref err) => write!(f, "{}", err),

compiler/rustc_mir/src/const_eval/error.rs

@@ -141,7 +141,7 @@ impl<'tcx> ConstEvalErr<'tcx> {
             err_inval!(Layout(LayoutError::Unknown(_))) | err_inval!(TooGeneric) => {
                 return ErrorHandled::TooGeneric;
             }
-            err_inval!(TypeckError(error_reported)) => {
+            err_inval!(AlreadyReported(error_reported)) => {
                 return ErrorHandled::Reported(error_reported);
             }
             // We must *always* hard error on these, even if the caller wants just a lint.

compiler/rustc_mir/src/const_eval/eval_queries.rs

@@ -67,7 +67,7 @@ fn eval_body_using_ecx<'mir, 'tcx>(
             None => InternKind::Constant,
         }
     };
-    intern_const_alloc_recursive(ecx, intern_kind, ret);
+    intern_const_alloc_recursive(ecx, intern_kind, ret)?;
 
     debug!("eval_body_using_ecx done: {:?}", *ret);
     Ok(ret)

compiler/rustc_mir/src/const_eval/mod.rs

@@ -29,7 +29,9 @@ pub(crate) fn const_caller_location(
     let mut ecx = mk_eval_cx(tcx, DUMMY_SP, ty::ParamEnv::reveal_all(), false);
 
     let loc_place = ecx.alloc_caller_location(file, line, col);
-    intern_const_alloc_recursive(&mut ecx, InternKind::Constant, loc_place);
+    if intern_const_alloc_recursive(&mut ecx, InternKind::Constant, loc_place).is_err() {
+        bug!("intern_const_alloc_recursive should not error in this case")
+    }
     ConstValue::Scalar(loc_place.ptr)
 }
 

compiler/rustc_mir/src/interpret/eval_context.rs

@@ -471,7 +471,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         if let Some(def) = def.as_local() {
             if self.tcx.has_typeck_results(def.did) {
                 if let Some(error_reported) = self.tcx.typeck_opt_const_arg(def).tainted_by_errors {
-                    throw_inval!(TypeckError(error_reported))
+                    throw_inval!(AlreadyReported(error_reported))
                 }
             }
         }
@@ -527,8 +527,8 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             Ok(Some(instance)) => Ok(instance),
             Ok(None) => throw_inval!(TooGeneric),
 
-            // FIXME(eddyb) this could be a bit more specific than `TypeckError`.
-            Err(error_reported) => throw_inval!(TypeckError(error_reported)),
+            // FIXME(eddyb) this could be a bit more specific than `AlreadyReported`.
+            Err(error_reported) => throw_inval!(AlreadyReported(error_reported)),
         }
     }
 

compiler/rustc_mir/src/interpret/intern.rs

@@ -16,6 +16,7 @@
 
 use super::validity::RefTracking;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_errors::ErrorReported;
 use rustc_hir as hir;
 use rustc_middle::mir::interpret::InterpResult;
 use rustc_middle::ty::{self, layout::TyAndLayout, Ty};
@@ -285,11 +286,13 @@ pub enum InternKind {
 /// tracks where in the value we are and thus can show much better error messages.
 /// Any errors here would anyway be turned into `const_err` lints, whereas validation failures
 /// are hard errors.
+#[tracing::instrument(skip(ecx))]
 pub fn intern_const_alloc_recursive<M: CompileTimeMachine<'mir, 'tcx>>(
     ecx: &mut InterpCx<'mir, 'tcx, M>,
     intern_kind: InternKind,
     ret: MPlaceTy<'tcx>,
-) where
+) -> Result<(), ErrorReported>
+where
     'tcx: 'mir,
 {
     let tcx = ecx.tcx;
@@ -405,12 +408,14 @@ pub fn intern_const_alloc_recursive<M: CompileTimeMachine<'mir, 'tcx>>(
             // Codegen does not like dangling pointers, and generally `tcx` assumes that
             // all allocations referenced anywhere actually exist. So, make sure we error here.
             ecx.tcx.sess.span_err(ecx.tcx.span, "encountered dangling pointer in final constant");
+            return Err(ErrorReported);
         } else if ecx.tcx.get_global_alloc(alloc_id).is_none() {
             // We have hit an `AllocId` that is neither in local or global memory and isn't
             // marked as dangling by local memory.  That should be impossible.
             span_bug!(ecx.tcx.span, "encountered unknown alloc id {:?}", alloc_id);
         }
     }
+    Ok(())
 }
 
 impl<'mir, 'tcx: 'mir, M: super::intern::CompileTimeMachine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {

compiler/rustc_mir/src/interpret/operand.rs

@@ -550,7 +550,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         // Early-return cases.
         let val_val = match val.val {
             ty::ConstKind::Param(_) | ty::ConstKind::Bound(..) => throw_inval!(TooGeneric),
-            ty::ConstKind::Error(_) => throw_inval!(TypeckError(ErrorReported)),
+            ty::ConstKind::Error(_) => throw_inval!(AlreadyReported(ErrorReported)),
             ty::ConstKind::Unevaluated(def, substs, promoted) => {
                 let instance = self.resolve(def, substs)?;
                 return Ok(self.eval_to_allocation(GlobalId { instance, promoted })?.into());

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

@@ -0,0 +1,10 @@
+const FOO: *const u32 = { //~ ERROR encountered dangling pointer in final constant
+    let x;
+    &x //~ ERROR borrow of possibly-uninitialized variable: `x`
+};
+
+fn main() {
+    let FOO = FOO;
+    //~^ ERROR could not evaluate constant pattern
+    //~| ERROR could not evaluate constant pattern
+}

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

@@ -0,0 +1,30 @@
+error[E0381]: borrow of possibly-uninitialized variable: `x`
+  --> $DIR/issue-78655.rs:3:5
+   |
+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
+   |
+LL |     let FOO = FOO;
+   |         ^^^
+
+error: could not evaluate constant pattern
+  --> $DIR/issue-78655.rs:7:9
+   |
+LL |     let FOO = FOO;
+   |         ^^^
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0381`.