Require any function with a tait in its signature to actually constrain a hidden type

Author: oli-obk

compiler/rustc_codegen_cranelift/example/issue-72793.rs

@@ -2,20 +2,23 @@
 
 #![feature(type_alias_impl_trait)]
 
-trait T {
-    type Item;
-}
+mod helper {
+    pub trait T {
+        type Item;
+    }
 
-type Alias<'a> = impl T<Item = &'a ()>;
+    pub type Alias<'a> = impl T<Item = &'a ()>;
 
-struct S;
-impl<'a> T for &'a S {
-    type Item = &'a ();
-}
+    struct S;
+    impl<'a> T for &'a S {
+        type Item = &'a ();
+    }
 
-fn filter_positive<'a>() -> Alias<'a> {
-    &S
+    pub fn filter_positive<'a>() -> Alias<'a> {
+        &S
+    }
 }
+use helper::*;
 
 fn with_positive(fun: impl Fn(Alias<'_>)) {
     fun(filter_positive());

compiler/rustc_data_structures/src/obligation_forest/mod.rs

@@ -146,8 +146,6 @@ pub enum ProcessResult<O, E> {
 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
 struct ObligationTreeId(usize);
 
-type ObligationTreeIdGenerator = impl Iterator<Item = ObligationTreeId>;
-
 pub struct ObligationForest<O: ForestObligation> {
     /// The list of obligations. In between calls to [Self::process_obligations],
     /// this list only contains nodes in the `Pending` or `Waiting` state.
@@ -310,18 +308,25 @@ pub struct Error<O, E> {
     pub backtrace: Vec<O>,
 }
 
-impl<O: ForestObligation> ObligationForest<O> {
-    pub fn new() -> ObligationForest<O> {
-        ObligationForest {
-            nodes: vec![],
-            done_cache: Default::default(),
-            active_cache: Default::default(),
-            reused_node_vec: vec![],
-            obligation_tree_id_generator: (0..).map(ObligationTreeId),
-            error_cache: Default::default(),
+mod helper {
+    use super::*;
+    pub type ObligationTreeIdGenerator = impl Iterator<Item = ObligationTreeId>;
+    impl<O: ForestObligation> ObligationForest<O> {
+        pub fn new() -> ObligationForest<O> {
+            ObligationForest {
+                nodes: vec![],
+                done_cache: Default::default(),
+                active_cache: Default::default(),
+                reused_node_vec: vec![],
+                obligation_tree_id_generator: (0..).map(ObligationTreeId),
+                error_cache: Default::default(),
+            }
         }
     }
+}
+use helper::*;
 
+impl<O: ForestObligation> ObligationForest<O> {
     /// Returns the total number of nodes in the forest that have not
     /// yet been fully resolved.
     pub fn len(&self) -> usize {

compiler/rustc_hir_analysis/messages.ftl

@@ -460,6 +460,10 @@ hir_analysis_static_specialize = cannot specialize on `'static` lifetime
 hir_analysis_tait_forward_compat = item constrains opaque type that is not in its signature
     .note = this item must mention the opaque type in its signature in order to be able to register hidden types
 
+hir_analysis_tait_forward_compat2 = item does not constrain `{$opaque_type}`, but has it in its signature
+    .note = consider moving the opaque type's declaration and defining uses into a separate module
+    .opaque = this opaque type is in the signature
+
 hir_analysis_target_feature_on_main = `main` function is not allowed to have `#[target_feature]`
 
 hir_analysis_too_large_static = extern static is too large for the current architecture

compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs

@@ -8,7 +8,7 @@ use rustc_middle::hir::nested_filter;
 use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitableExt};
 use rustc_span::{sym, ErrorGuaranteed, DUMMY_SP};
 
-use crate::errors::{TaitForwardCompat, TypeOf, UnconstrainedOpaqueType};
+use crate::errors::{TaitForwardCompat, TaitForwardCompat2, TypeOf, UnconstrainedOpaqueType};
 
 pub fn test_opaque_hidden_types(tcx: TyCtxt<'_>) -> Result<(), ErrorGuaranteed> {
     let mut res = Ok(());
@@ -229,13 +229,14 @@ impl TaitConstraintLocator<'_> {
             return;
         }
 
+        let opaque_types_defined_by = self.tcx.opaque_types_defined_by(item_def_id);
+
         let mut constrained = false;
         for (&opaque_type_key, &hidden_type) in &tables.concrete_opaque_types {
             if opaque_type_key.def_id != self.def_id {
                 continue;
             }
             constrained = true;
-            let opaque_types_defined_by = self.tcx.opaque_types_defined_by(item_def_id);
 
             if !opaque_types_defined_by.contains(&self.def_id) {
                 self.tcx.dcx().emit_err(TaitForwardCompat {
@@ -259,6 +260,16 @@ impl TaitConstraintLocator<'_> {
 
         if !constrained {
             debug!("no constraints in typeck results");
+            if opaque_types_defined_by.contains(&self.def_id) {
+                self.tcx.dcx().emit_err(TaitForwardCompat2 {
+                    span: self
+                        .tcx
+                        .def_ident_span(item_def_id)
+                        .unwrap_or_else(|| self.tcx.def_span(item_def_id)),
+                    opaque_type_span: self.tcx.def_span(self.def_id),
+                    opaque_type: self.tcx.def_path_str(self.def_id),
+                });
+            }
             return;
         };
 

compiler/rustc_hir_analysis/src/errors.rs

@@ -390,6 +390,17 @@ pub struct TaitForwardCompat {
     pub item_span: Span,
 }
 
+#[derive(Diagnostic)]
+#[diag(hir_analysis_tait_forward_compat2)]
+#[note]
+pub struct TaitForwardCompat2 {
+    #[primary_span]
+    pub span: Span,
+    #[note(hir_analysis_opaque)]
+    pub opaque_type_span: Span,
+    pub opaque_type: String,
+}
+
 pub struct MissingTypeParams {
     pub span: Span,
     pub def_span: Span,

compiler/rustc_middle/src/mir/terminator.rs

@@ -377,9 +377,6 @@ pub struct Terminator<'tcx> {
     pub kind: TerminatorKind<'tcx>,
 }
 
-pub type Successors<'a> = impl DoubleEndedIterator<Item = BasicBlock> + 'a;
-pub type SuccessorsMut<'a> = impl DoubleEndedIterator<Item = &'a mut BasicBlock> + 'a;
-
 impl<'tcx> Terminator<'tcx> {
     #[inline]
     pub fn successors(&self) -> Successors<'_> {
@@ -407,81 +404,95 @@ impl<'tcx> TerminatorKind<'tcx> {
     pub fn if_(cond: Operand<'tcx>, t: BasicBlock, f: BasicBlock) -> TerminatorKind<'tcx> {
         TerminatorKind::SwitchInt { discr: cond, targets: SwitchTargets::static_if(0, f, t) }
     }
+}
 
-    #[inline]
-    pub fn successors(&self) -> Successors<'_> {
-        use self::TerminatorKind::*;
-        match *self {
-            Call { target: Some(ref t), unwind: UnwindAction::Cleanup(u), .. }
-            | Yield { resume: ref t, drop: Some(u), .. }
-            | Drop { target: ref t, unwind: UnwindAction::Cleanup(u), .. }
-            | Assert { target: ref t, unwind: UnwindAction::Cleanup(u), .. }
-            | FalseUnwind { real_target: ref t, unwind: UnwindAction::Cleanup(u) } => {
-                slice::from_ref(t).into_iter().copied().chain(Some(u))
-            }
-            Goto { target: ref t }
-            | Call { target: None, unwind: UnwindAction::Cleanup(ref t), .. }
-            | Call { target: Some(ref t), unwind: _, .. }
-            | Yield { resume: ref t, drop: None, .. }
-            | Drop { target: ref t, unwind: _, .. }
-            | Assert { target: ref t, unwind: _, .. }
-            | FalseUnwind { real_target: ref t, unwind: _ } => {
-                slice::from_ref(t).into_iter().copied().chain(None)
-            }
-            UnwindResume
-            | UnwindTerminate(_)
-            | CoroutineDrop
-            | Return
-            | Unreachable
-            | Call { target: None, unwind: _, .. } => (&[]).into_iter().copied().chain(None),
-            InlineAsm { ref targets, unwind: UnwindAction::Cleanup(u), .. } => {
-                targets.iter().copied().chain(Some(u))
-            }
-            InlineAsm { ref targets, unwind: _, .. } => targets.iter().copied().chain(None),
-            SwitchInt { ref targets, .. } => targets.targets.iter().copied().chain(None),
-            FalseEdge { ref real_target, imaginary_target } => {
-                slice::from_ref(real_target).into_iter().copied().chain(Some(imaginary_target))
+pub use helper::*;
+
+mod helper {
+    use super::*;
+    pub type Successors<'a> = impl DoubleEndedIterator<Item = BasicBlock> + 'a;
+    pub type SuccessorsMut<'a> = impl DoubleEndedIterator<Item = &'a mut BasicBlock> + 'a;
+    impl<'tcx> TerminatorKind<'tcx> {
+        #[inline]
+        pub fn successors(&self) -> Successors<'_> {
+            use self::TerminatorKind::*;
+            match *self {
+                Call { target: Some(ref t), unwind: UnwindAction::Cleanup(u), .. }
+                | Yield { resume: ref t, drop: Some(u), .. }
+                | Drop { target: ref t, unwind: UnwindAction::Cleanup(u), .. }
+                | Assert { target: ref t, unwind: UnwindAction::Cleanup(u), .. }
+                | FalseUnwind { real_target: ref t, unwind: UnwindAction::Cleanup(u) } => {
+                    slice::from_ref(t).into_iter().copied().chain(Some(u))
+                }
+                Goto { target: ref t }
+                | Call { target: None, unwind: UnwindAction::Cleanup(ref t), .. }
+                | Call { target: Some(ref t), unwind: _, .. }
+                | Yield { resume: ref t, drop: None, .. }
+                | Drop { target: ref t, unwind: _, .. }
+                | Assert { target: ref t, unwind: _, .. }
+                | FalseUnwind { real_target: ref t, unwind: _ } => {
+                    slice::from_ref(t).into_iter().copied().chain(None)
+                }
+                UnwindResume
+                | UnwindTerminate(_)
+                | CoroutineDrop
+                | Return
+                | Unreachable
+                | Call { target: None, unwind: _, .. } => (&[]).into_iter().copied().chain(None),
+                InlineAsm { ref targets, unwind: UnwindAction::Cleanup(u), .. } => {
+                    targets.iter().copied().chain(Some(u))
+                }
+                InlineAsm { ref targets, unwind: _, .. } => targets.iter().copied().chain(None),
+                SwitchInt { ref targets, .. } => targets.targets.iter().copied().chain(None),
+                FalseEdge { ref real_target, imaginary_target } => {
+                    slice::from_ref(real_target).into_iter().copied().chain(Some(imaginary_target))
+                }
             }
         }
-    }
 
-    #[inline]
-    pub fn successors_mut(&mut self) -> SuccessorsMut<'_> {
-        use self::TerminatorKind::*;
-        match *self {
-            Call { target: Some(ref mut t), unwind: UnwindAction::Cleanup(ref mut u), .. }
-            | Yield { resume: ref mut t, drop: Some(ref mut u), .. }
-            | Drop { target: ref mut t, unwind: UnwindAction::Cleanup(ref mut u), .. }
-            | Assert { target: ref mut t, unwind: UnwindAction::Cleanup(ref mut u), .. }
-            | FalseUnwind { real_target: ref mut t, unwind: UnwindAction::Cleanup(ref mut u) } => {
-                slice::from_mut(t).into_iter().chain(Some(u))
-            }
-            Goto { target: ref mut t }
-            | Call { target: None, unwind: UnwindAction::Cleanup(ref mut t), .. }
-            | Call { target: Some(ref mut t), unwind: _, .. }
-            | Yield { resume: ref mut t, drop: None, .. }
-            | Drop { target: ref mut t, unwind: _, .. }
-            | Assert { target: ref mut t, unwind: _, .. }
-            | FalseUnwind { real_target: ref mut t, unwind: _ } => {
-                slice::from_mut(t).into_iter().chain(None)
-            }
-            UnwindResume
-            | UnwindTerminate(_)
-            | CoroutineDrop
-            | Return
-            | Unreachable
-            | Call { target: None, unwind: _, .. } => (&mut []).into_iter().chain(None),
-            InlineAsm { ref mut targets, unwind: UnwindAction::Cleanup(ref mut u), .. } => {
-                targets.iter_mut().chain(Some(u))
-            }
-            InlineAsm { ref mut targets, unwind: _, .. } => targets.iter_mut().chain(None),
-            SwitchInt { ref mut targets, .. } => targets.targets.iter_mut().chain(None),
-            FalseEdge { ref mut real_target, ref mut imaginary_target } => {
-                slice::from_mut(real_target).into_iter().chain(Some(imaginary_target))
+        #[inline]
+        pub fn successors_mut(&mut self) -> SuccessorsMut<'_> {
+            use self::TerminatorKind::*;
+            match *self {
+                Call {
+                    target: Some(ref mut t), unwind: UnwindAction::Cleanup(ref mut u), ..
+                }
+                | Yield { resume: ref mut t, drop: Some(ref mut u), .. }
+                | Drop { target: ref mut t, unwind: UnwindAction::Cleanup(ref mut u), .. }
+                | Assert { target: ref mut t, unwind: UnwindAction::Cleanup(ref mut u), .. }
+                | FalseUnwind {
+                    real_target: ref mut t,
+                    unwind: UnwindAction::Cleanup(ref mut u),
+                } => slice::from_mut(t).into_iter().chain(Some(u)),
+                Goto { target: ref mut t }
+                | Call { target: None, unwind: UnwindAction::Cleanup(ref mut t), .. }
+                | Call { target: Some(ref mut t), unwind: _, .. }
+                | Yield { resume: ref mut t, drop: None, .. }
+                | Drop { target: ref mut t, unwind: _, .. }
+                | Assert { target: ref mut t, unwind: _, .. }
+                | FalseUnwind { real_target: ref mut t, unwind: _ } => {
+                    slice::from_mut(t).into_iter().chain(None)
+                }
+                UnwindResume
+                | UnwindTerminate(_)
+                | CoroutineDrop
+                | Return
+                | Unreachable
+                | Call { target: None, unwind: _, .. } => (&mut []).into_iter().chain(None),
+                InlineAsm { ref mut targets, unwind: UnwindAction::Cleanup(ref mut u), .. } => {
+                    targets.iter_mut().chain(Some(u))
+                }
+                InlineAsm { ref mut targets, unwind: _, .. } => targets.iter_mut().chain(None),
+                SwitchInt { ref mut targets, .. } => targets.targets.iter_mut().chain(None),
+                FalseEdge { ref mut real_target, ref mut imaginary_target } => {
+                    slice::from_mut(real_target).into_iter().chain(Some(imaginary_target))
+                }
             }
         }
     }
+}
 
+impl<'tcx> TerminatorKind<'tcx> {
     #[inline]
     pub fn unwind(&self) -> Option<&UnwindAction> {
         match *self {

library/std/src/backtrace.rs

@@ -428,39 +428,43 @@ impl fmt::Display for Backtrace {
     }
 }
 
-type LazyResolve = impl (FnOnce() -> Capture) + Send + Sync + UnwindSafe;
-
-fn lazy_resolve(mut capture: Capture) -> LazyResolve {
-    move || {
-        // Use the global backtrace lock to synchronize this as it's a
-        // requirement of the `backtrace` crate, and then actually resolve
-        // everything.
-        let _lock = lock();
-        for frame in capture.frames.iter_mut() {
-            let symbols = &mut frame.symbols;
-            let frame = match &frame.frame {
-                RawFrame::Actual(frame) => frame,
-                #[cfg(test)]
-                RawFrame::Fake => unimplemented!(),
-            };
-            unsafe {
-                backtrace_rs::resolve_frame_unsynchronized(frame, |symbol| {
-                    symbols.push(BacktraceSymbol {
-                        name: symbol.name().map(|m| m.as_bytes().to_vec()),
-                        filename: symbol.filename_raw().map(|b| match b {
-                            BytesOrWideString::Bytes(b) => BytesOrWide::Bytes(b.to_owned()),
-                            BytesOrWideString::Wide(b) => BytesOrWide::Wide(b.to_owned()),
-                        }),
-                        lineno: symbol.lineno(),
-                        colno: symbol.colno(),
+mod helper {
+    use super::*;
+    pub(super) type LazyResolve = impl (FnOnce() -> Capture) + Send + Sync + UnwindSafe;
+
+    pub(super) fn lazy_resolve(mut capture: Capture) -> LazyResolve {
+        move || {
+            // Use the global backtrace lock to synchronize this as it's a
+            // requirement of the `backtrace` crate, and then actually resolve
+            // everything.
+            let _lock = lock();
+            for frame in capture.frames.iter_mut() {
+                let symbols = &mut frame.symbols;
+                let frame = match &frame.frame {
+                    RawFrame::Actual(frame) => frame,
+                    #[cfg(test)]
+                    RawFrame::Fake => unimplemented!(),
+                };
+                unsafe {
+                    backtrace_rs::resolve_frame_unsynchronized(frame, |symbol| {
+                        symbols.push(BacktraceSymbol {
+                            name: symbol.name().map(|m| m.as_bytes().to_vec()),
+                            filename: symbol.filename_raw().map(|b| match b {
+                                BytesOrWideString::Bytes(b) => BytesOrWide::Bytes(b.to_owned()),
+                                BytesOrWideString::Wide(b) => BytesOrWide::Wide(b.to_owned()),
+                            }),
+                            lineno: symbol.lineno(),
+                            colno: symbol.colno(),
+                        });
                     });
-                });
+                }
             }
-        }
 
-        capture
+            capture
+        }
     }
 }
+use helper::*;
 
 impl RawFrame {
     fn ip(&self) -> *mut c_void {