Run const_prop_lint in check builds, too

Author: oli-obk

compiler/rustc_interface/src/passes.rs

@@ -734,6 +734,8 @@ 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().const_prop_lint_promoteds(def_id);
             tcx.ensure().mir_borrowck(def_id)
         });
     });

compiler/rustc_middle/src/mir/tcx.rs

@@ -76,6 +76,10 @@ impl<'tcx> PlaceTy<'tcx> {
         if self.variant_index.is_some() && !matches!(elem, ProjectionElem::Field(..)) {
             bug!("cannot use non field projection on downcasted place")
         }
+        if self.ty.references_error() {
+            // Cannot do anything useful with error types
+            return PlaceTy::from_ty(self.ty);
+        }
         let answer = match *elem {
             ProjectionElem::Deref => {
                 let ty = self

compiler/rustc_middle/src/query/erase.rs

@@ -243,6 +243,7 @@ trivial! {
     Option<usize>,
     Option<rustc_span::Symbol>,
     Result<(), rustc_errors::ErrorGuaranteed>,
+    Result<(), traits::util::HasImpossiblePredicates>,
     Result<(), rustc_middle::traits::query::NoSolution>,
     Result<rustc_middle::traits::EvaluationResult, rustc_middle::traits::OverflowError>,
     rustc_ast::expand::allocator::AllocatorKind,

compiler/rustc_middle/src/query/mod.rs

@@ -40,6 +40,7 @@ use crate::traits::query::{
     OutlivesBound,
 };
 use crate::traits::specialization_graph;
+use crate::traits::util::HasImpossiblePredicates;
 use crate::traits::{
     CodegenObligationError, EvaluationResult, ImplSource, ObjectSafetyViolation, ObligationCause,
     OverflowError, WellFormedLoc,
@@ -1015,6 +1016,18 @@ 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) -> Result<(), HasImpossiblePredicates> {
+        desc { |tcx| "running const prop lints for `{}`", tcx.def_path_str(key) }
+        cache_on_disk_if { true }
+    }
+
+    /// Run the const prop lints on the promoted consts of an item.
+    query const_prop_lint_promoteds(key: LocalDefId) -> Result<(), HasImpossiblePredicates> {
+        desc { |tcx| "running const prop lints for promoteds of `{}`", 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_middle/src/traits/util.rs

@@ -60,3 +60,9 @@ impl<'tcx> Iterator for Elaborator<'tcx> {
         }
     }
 }
+
+/// Used as an error type to signal that an item may have an invalid body, because its
+/// where bounds are trivially not satisfyable.
+#[derive(Clone, Copy, Debug, Hash, PartialEq, Eq, PartialOrd, Ord)]
+#[derive(HashStable, Encodable, Decodable)]
+pub struct HasImpossiblePredicates;

compiler/rustc_middle/src/ty/util.rs

@@ -659,10 +659,17 @@ impl<'tcx> TyCtxt<'tcx> {
     /// Get the type of the pointer to the static that we use in MIR.
     pub fn static_ptr_ty(self, def_id: DefId) -> Ty<'tcx> {
         // Make sure that any constants in the static's type are evaluated.
-        let static_ty = self.normalize_erasing_regions(
+        let mut static_ty = self.normalize_erasing_regions(
             ty::ParamEnv::empty(),
             self.type_of(def_id).instantiate_identity(),
         );
+        if !static_ty.is_sized(self, ty::ParamEnv::reveal_all()) {
+            static_ty = Ty::new_error_with_message(
+                self,
+                self.def_span(def_id),
+                "unsized statics are forbidden and error in wfcheck",
+            );
+        }
 
         // Make sure that accesses to unsafe statics end up using raw pointers.
         // For thread-locals, this needs to be kept in sync with `Rvalue::ty`.

compiler/rustc_mir_transform/src/const_prop_lint.rs

@@ -261,6 +261,11 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
         // manually normalized.
         let val = self.tcx.try_normalize_erasing_regions(self.param_env, c.const_).ok()?;
 
+        // Unsized constants are illegal and already errored in wfcheck
+        if !val.ty().is_sized(self.tcx, self.param_env) {
+            return None;
+        }
+
         self.use_ecx(|this| this.ecx.eval_mir_constant(&val, Some(c.span), None))?
             .as_mplace_or_imm()
             .right()
@@ -471,6 +476,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
         let value_const = self.use_ecx(|this| this.ecx.read_scalar(value))?;
 
         if expected != value_const {
+            trace!("assertion failed");
             // Poison all places this operand references so that further code
             // doesn't use the invalid value
             if let Some(place) = cond.place() {

compiler/rustc_mir_transform/src/lib.rs

@@ -38,6 +38,7 @@ use rustc_middle::mir::{
     SourceInfo, Statement, StatementKind, TerminatorKind, START_BLOCK,
 };
 use rustc_middle::query::Providers;
+use rustc_middle::traits::util::HasImpossiblePredicates;
 use rustc_middle::ty::{self, TyCtxt, TypeVisitableExt};
 use rustc_span::{source_map::Spanned, sym, DUMMY_SP};
 use rustc_trait_selection::traits;
@@ -137,6 +138,8 @@ 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,
+        const_prop_lint_promoteds,
         promoted_mir,
         deduced_param_attrs: deduce_param_attrs::deduced_param_attrs,
         ..*providers
@@ -393,6 +396,39 @@ fn inner_mir_for_ctfe(tcx: TyCtxt<'_>, def: LocalDefId) -> Body<'_> {
     body
 }
 
+fn const_prop_lint(tcx: TyCtxt<'_>, def: LocalDefId) -> Result<(), HasImpossiblePredicates> {
+    let (body, _) = tcx.mir_promoted(def);
+    let body = body.borrow();
+
+    let mir_borrowck = tcx.mir_borrowck(def);
+
+    check_impossible_predicates(tcx, def)?;
+    if mir_borrowck.tainted_by_errors.is_none() && body.tainted_by_errors.is_none() {
+        const_prop_lint::ConstPropLint.run_lint(tcx, &body);
+    }
+    Ok(())
+}
+
+fn const_prop_lint_promoteds(
+    tcx: TyCtxt<'_>,
+    def: LocalDefId,
+) -> Result<(), HasImpossiblePredicates> {
+    let (_, promoteds) = tcx.mir_promoted(def);
+    let promoteds = promoteds.borrow();
+
+    let mir_borrowck = tcx.mir_borrowck(def);
+
+    check_impossible_predicates(tcx, def)?;
+    if mir_borrowck.tainted_by_errors.is_none() {
+        for body in &*promoteds {
+            if body.tainted_by_errors.is_none() {
+                const_prop_lint::ConstPropLint.run_lint(tcx, &body);
+            }
+        }
+    }
+    Ok(())
+}
+
 /// 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.
@@ -401,6 +437,7 @@ 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);
+    let impossible_predicates = tcx.const_prop_lint(def);
 
     let is_fn_like = tcx.def_kind(def).is_fn_like();
     if is_fn_like {
@@ -415,7 +452,30 @@ fn mir_drops_elaborated_and_const_checked(tcx: TyCtxt<'_>, def: LocalDefId) -> &
     if let Some(error_reported) = mir_borrowck.tainted_by_errors {
         body.tainted_by_errors = Some(error_reported);
     }
+    if impossible_predicates.is_err() {
+        trace!("found unsatisfiable predicates for {:?}", body.source);
+        // Clear the body to only contain a single `unreachable` statement.
+        let bbs = body.basic_blocks.as_mut();
+        bbs.raw.truncate(1);
+        bbs[START_BLOCK].statements.clear();
+        bbs[START_BLOCK].terminator_mut().kind = TerminatorKind::Unreachable;
+        body.var_debug_info.clear();
+        body.local_decls.raw.truncate(body.arg_count + 1);
+    }
 
+    run_analysis_to_runtime_passes(tcx, &mut body);
+
+    // Now that drop elaboration has been performed, we can check for
+    // unconditional drop recursion.
+    rustc_mir_build::lints::check_drop_recursion(tcx, &body);
+
+    tcx.alloc_steal_mir(body)
+}
+
+fn check_impossible_predicates(
+    tcx: TyCtxt<'_>,
+    def: LocalDefId,
+) -> Result<(), HasImpossiblePredicates> {
     // Check if it's even possible to satisfy the 'where' clauses
     // for this item.
     //
@@ -445,28 +505,15 @@ fn mir_drops_elaborated_and_const_checked(tcx: TyCtxt<'_>, def: LocalDefId) -> &
     // the normalization code (leading to cycle errors), since
     // it's usually never invoked in this way.
     let predicates = tcx
-        .predicates_of(body.source.def_id())
+        .predicates_of(def)
         .predicates
         .iter()
         .filter_map(|(p, _)| if p.is_global() { Some(*p) } else { None });
     if traits::impossible_predicates(tcx, traits::elaborate(tcx, predicates).collect()) {
-        trace!("found unsatisfiable predicates for {:?}", body.source);
-        // Clear the body to only contain a single `unreachable` statement.
-        let bbs = body.basic_blocks.as_mut();
-        bbs.raw.truncate(1);
-        bbs[START_BLOCK].statements.clear();
-        bbs[START_BLOCK].terminator_mut().kind = TerminatorKind::Unreachable;
-        body.var_debug_info.clear();
-        body.local_decls.raw.truncate(body.arg_count + 1);
+        Err(HasImpossiblePredicates)
+    } else {
+        Ok(())
     }
-
-    run_analysis_to_runtime_passes(tcx, &mut body);
-
-    // Now that drop elaboration has been performed, we can check for
-    // unconditional drop recursion.
-    rustc_mir_build::lints::check_drop_recursion(tcx, &body);
-
-    tcx.alloc_steal_mir(body)
 }
 
 // Made public such that `mir_drops_elaborated_and_const_checked` can be overridden
@@ -533,7 +580,6 @@ 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)));
 }
@@ -678,6 +724,7 @@ fn promoted_mir(tcx: TyCtxt<'_>, def: LocalDefId) -> &IndexVec<Promoted, Body<'_
     }
 
     tcx.ensure_with_value().mir_borrowck(def);
+    tcx.ensure().const_prop_lint_promoteds(def);
     let mut promoted = tcx.mir_promoted(def).1.steal();
 
     for body in &mut promoted {

src/doc/rustc/src/lints/levels.md

@@ -71,7 +71,7 @@ level is capped via cap-lints.
 A 'deny' lint produces an error if you violate it. For example, this code
 runs into the `exceeding_bitshifts` lint.
 
-```rust,no_run
+```rust,compile_fail
 fn main() {
     100u8 << 10;
 }
@@ -246,7 +246,7 @@ pub fn foo() {}
 This is the maximum level for all lints. So for example, if we take our
 code sample from the "deny" lint level above:
 
-```rust,no_run
+```rust,compile_fail
 fn main() {
     100u8 << 10;
 }

src/tools/clippy/tests/ui-toml/suppress_lint_in_const/test.rs

@@ -35,9 +35,8 @@ fn main() {
     x[const { idx() }]; // Ok, should not produce stderr.
     x[const { idx4() }]; // Ok, let rustc's `unconditional_panic` lint handle `usize` indexing on arrays.
     const { &ARR[idx()] }; // Ok, should not produce stderr, since `suppress-restriction-lint-in-const` is set true.
-    const { &ARR[idx4()] }; // Ok, should not produce stderr, since `suppress-restriction-lint-in-const` is set true.
-    //
-    //~^^ ERROR: failed
+    // FIXME errors in rustc and subsequently blocks all lints in this file. Can reenable once solved on the rustc side
+    //const { &ARR[idx4()] }; // Ok, should not produce stderr, since `suppress-restriction-lint-in-const` is set true.
 
     let y = &x;
     y[0]; // Ok, referencing shouldn't affect this lint. See the issue 6021