Auto merge of rust-lang#120687 - oli-obk:early_const_prop, r=<try>

Run const_prop_lint in check builds, too

implements rust-lang#108730 (comment)

Turns the const_prop_lint pass into a query that is run alongside borrowck.

Author: bors

compiler/rustc_abi/src/layout.rs

@@ -426,10 +426,11 @@ where
                 }
             }
         }
-        _ => assert!(
-            start == Bound::Unbounded && end == Bound::Unbounded,
-            "nonscalar layout for layout_scalar_valid_range type: {st:#?}",
-        ),
+        _ => {
+            if start != Bound::Unbounded || end != Bound::Unbounded {
+                return None;
+            }
+        }
     }
 
     Some(st)

compiler/rustc_interface/src/passes.rs

@@ -738,6 +738,7 @@ fn analysis(tcx: TyCtxt<'_>, (): ()) -> Result<()> {
             // Run unsafety check because it's responsible for stealing and
             // deallocating THIR.
             tcx.ensure().check_unsafety(def_id);
+            tcx.ensure().const_prop_lint(def_id);
             tcx.ensure().mir_borrowck(def_id)
         });
     });

compiler/rustc_middle/src/query/mod.rs

@@ -1013,6 +1013,12 @@ rustc_queries! {
         cache_on_disk_if(tcx) { tcx.is_typeck_child(key.to_def_id()) }
     }
 
+    /// Run the const prop lints on the `mir_promoted` of an item.
+    query const_prop_lint(key: LocalDefId) {
+        desc { |tcx| "checking const prop lints for `{}`", tcx.def_path_str(key) }
+        cache_on_disk_if { true }
+    }
+
     /// Gets a complete map from all types to their inherent impls.
     /// Not meant to be used directly outside of coherence.
     query crate_inherent_impls(k: ()) -> Result<&'tcx CrateInherentImpls, ErrorGuaranteed> {

compiler/rustc_mir_transform/src/lib.rs

@@ -142,6 +142,7 @@ pub fn provide(providers: &mut Providers) {
         is_ctfe_mir_available: |tcx, did| is_mir_available(tcx, did),
         mir_callgraph_reachable: inline::cycle::mir_callgraph_reachable,
         mir_inliner_callees: inline::cycle::mir_inliner_callees,
+        const_prop_lint,
         promoted_mir,
         deduced_param_attrs: deduce_param_attrs::deduced_param_attrs,
         ..*providers
@@ -394,6 +395,27 @@ fn inner_mir_for_ctfe(tcx: TyCtxt<'_>, def: LocalDefId) -> Body<'_> {
     body
 }
 
+fn const_prop_lint(tcx: TyCtxt<'_>, def: LocalDefId) {
+    let (body, _) = tcx.mir_promoted(def);
+    let body = body.borrow();
+
+    let mir_borrowck = tcx.mir_borrowck(def);
+
+    // If there are impossible bounds on the body being const prop linted,
+    // the const eval logic used in const prop may ICE unexpectedly.
+    let predicates = tcx
+        .predicates_of(body.source.def_id())
+        .predicates
+        .iter()
+        .filter_map(|(p, _)| if p.is_global() { Some(*p) } else { None });
+    if !traits::impossible_predicates(tcx, traits::elaborate(tcx, predicates).collect())
+        && mir_borrowck.tainted_by_errors.is_none()
+        && body.tainted_by_errors.is_none()
+    {
+        const_prop_lint::ConstPropLint.run_lint(tcx, &body);
+    }
+}
+
 /// Obtain just the main MIR (no promoteds) and run some cleanups on it. This also runs
 /// mir borrowck *before* doing so in order to ensure that borrowck can be run and doesn't
 /// end up missing the source MIR due to stealing happening.
@@ -402,6 +424,7 @@ fn mir_drops_elaborated_and_const_checked(tcx: TyCtxt<'_>, def: LocalDefId) -> &
         tcx.ensure_with_value().mir_coroutine_witnesses(def);
     }
     let mir_borrowck = tcx.mir_borrowck(def);
+    tcx.ensure().const_prop_lint(def);
 
     let is_fn_like = tcx.def_kind(def).is_fn_like();
     if is_fn_like {
@@ -534,7 +557,6 @@ fn run_runtime_lowering_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
         &elaborate_box_derefs::ElaborateBoxDerefs,
         &coroutine::StateTransform,
         &add_retag::AddRetag,
-        &Lint(const_prop_lint::ConstPropLint),
     ];
     pm::run_passes_no_validate(tcx, body, passes, Some(MirPhase::Runtime(RuntimePhase::Initial)));
 }

tests/ui/array-slice-vec/array_const_index-0.stderr

@@ -4,6 +4,20 @@ error[E0080]: evaluation of constant value failed
 LL | const B: i32 = (&A)[1];
    |                ^^^^^^^ index out of bounds: the length is 0 but the index is 1
 
+note: erroneous constant encountered
+  --> $DIR/array_const_index-0.rs:7:13
+   |
+LL |     let _ = B;
+   |             ^
+
+note: erroneous constant encountered
+  --> $DIR/array_const_index-0.rs:7:13
+   |
+LL |     let _ = B;
+   |             ^
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
 error: aborting due to 1 previous error
 
 For more information about this error, try `rustc --explain E0080`.

tests/ui/array-slice-vec/array_const_index-1.stderr

@@ -4,6 +4,20 @@ error[E0080]: evaluation of constant value failed
 LL | const B: i32 = A[1];
    |                ^^^^ index out of bounds: the length is 0 but the index is 1
 
+note: erroneous constant encountered
+  --> $DIR/array_const_index-1.rs:7:13
+   |
+LL |     let _ = B;
+   |             ^
+
+note: erroneous constant encountered
+  --> $DIR/array_const_index-1.rs:7:13
+   |
+LL |     let _ = B;
+   |             ^
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
 error: aborting due to 1 previous error
 
 For more information about this error, try `rustc --explain E0080`.

tests/ui/associated-consts/defaults-cyclic-fail.rs

@@ -1,5 +1,3 @@
-// build-fail
-
 // Cyclic assoc. const defaults don't error unless *used*
 trait Tr {
     const A: u8 = Self::B;

tests/ui/associated-consts/defaults-cyclic-fail.stderr

@@ -1,27 +1,27 @@
 error[E0391]: cycle detected when simplifying constant for the type system `Tr::A`
-  --> $DIR/defaults-cyclic-fail.rs:5:5
+  --> $DIR/defaults-cyclic-fail.rs:3:5
    |
 LL |     const A: u8 = Self::B;
    |     ^^^^^^^^^^^
    |
 note: ...which requires const-evaluating + checking `Tr::A`...
-  --> $DIR/defaults-cyclic-fail.rs:5:19
+  --> $DIR/defaults-cyclic-fail.rs:3:19
    |
 LL |     const A: u8 = Self::B;
    |                   ^^^^^^^
 note: ...which requires simplifying constant for the type system `Tr::B`...
-  --> $DIR/defaults-cyclic-fail.rs:8:5
+  --> $DIR/defaults-cyclic-fail.rs:6:5
    |
 LL |     const B: u8 = Self::A;
    |     ^^^^^^^^^^^
 note: ...which requires const-evaluating + checking `Tr::B`...
-  --> $DIR/defaults-cyclic-fail.rs:8:19
+  --> $DIR/defaults-cyclic-fail.rs:6:19
    |
 LL |     const B: u8 = Self::A;
    |                   ^^^^^^^
    = note: ...which again requires simplifying constant for the type system `Tr::A`, completing the cycle
 note: cycle used when const-evaluating + checking `main::promoted[1]`
-  --> $DIR/defaults-cyclic-fail.rs:16:16
+  --> $DIR/defaults-cyclic-fail.rs:14:16
    |
 LL |     assert_eq!(<() as Tr>::A, 0);
    |                ^^^^^^^^^^^^^

tests/ui/associated-consts/defaults-not-assumed-fail.rs

@@ -1,5 +1,3 @@
-// build-fail
-
 trait Tr {
     const A: u8 = 255;
 

tests/ui/associated-consts/defaults-not-assumed-fail.stderr

@@ -1,25 +1,25 @@
 error[E0080]: evaluation of `<() as Tr>::B` failed
-  --> $DIR/defaults-not-assumed-fail.rs:8:19
+  --> $DIR/defaults-not-assumed-fail.rs:6:19
    |
 LL |     const B: u8 = Self::A + 1;
    |                   ^^^^^^^^^^^ attempt to compute `u8::MAX + 1_u8`, which would overflow
 
 note: erroneous constant encountered
-  --> $DIR/defaults-not-assumed-fail.rs:33:16
+  --> $DIR/defaults-not-assumed-fail.rs:31:16
    |
 LL |     assert_eq!(<() as Tr>::B, 0);    // causes the error above
    |                ^^^^^^^^^^^^^
 
 note: erroneous constant encountered
-  --> $DIR/defaults-not-assumed-fail.rs:33:5
+  --> $DIR/defaults-not-assumed-fail.rs:31:5
    |
 LL |     assert_eq!(<() as Tr>::B, 0);    // causes the error above
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: this note originates in the macro `assert_eq` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 note: erroneous constant encountered
-  --> $DIR/defaults-not-assumed-fail.rs:33:5
+  --> $DIR/defaults-not-assumed-fail.rs:31:5
    |
 LL |     assert_eq!(<() as Tr>::B, 0);    // causes the error above
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^