unify dyn* coercions with other pointer coercions

Lukas Markeffsky · Lukas Markeffsky · commit e5c98fd5122e · 2024-09-15T19:35:59.000+02:00
diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs
@@ -2141,7 +2141,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                         );
                     }
 
-                    CastKind::DynStar => {
+                    CastKind::PointerCoercion(PointerCoercion::DynStar) => {
                         // get the constraints from the target type (`dyn* Clone`)
                         //
                         // apply them to prove that the source type `Foo` implements `Clone` etc
diff --git a/compiler/rustc_codegen_cranelift/src/base.rs b/compiler/rustc_codegen_cranelift/src/base.rs
@@ -770,7 +770,11 @@ fn codegen_stmt<'tcx>(
                     let operand = codegen_operand(fx, operand);
                     crate::unsize::coerce_unsized_into(fx, operand, lval);
                 }
-                Rvalue::Cast(CastKind::DynStar, ref operand, _) => {
+                Rvalue::Cast(
+                    CastKind::PointerCoercion(PointerCoercion::DynStar),
+                    ref operand,
+                    _,
+                ) => {
                     let operand = codegen_operand(fx, operand);
                     crate::unsize::coerce_dyn_star(fx, operand, lval);
                 }
diff --git a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
@@ -525,7 +525,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                             bug!("unexpected non-pair operand");
                         }
                     }
-                    mir::CastKind::DynStar => {
+                    mir::CastKind::PointerCoercion(PointerCoercion::DynStar) => {
                         let (lldata, llextra) = operand.val.pointer_parts();
                         let (lldata, llextra) =
                             base::cast_to_dyn_star(bx, lldata, operand.layout, cast.ty, llextra);
diff --git a/compiler/rustc_const_eval/src/check_consts/check.rs b/compiler/rustc_const_eval/src/check_consts/check.rs
@@ -447,8 +447,12 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                 // These are all okay; they only change the type, not the data.
             }
 
-            Rvalue::Cast(CastKind::PointerCoercion(PointerCoercion::Unsize), _, _) => {
-                // Unsizing is implemented for CTFE.
+            Rvalue::Cast(
+                CastKind::PointerCoercion(PointerCoercion::Unsize | PointerCoercion::DynStar),
+                _,
+                _,
+            ) => {
+                // Unsizing and `dyn*` coercions are implemented for CTFE.
             }
 
             Rvalue::Cast(CastKind::PointerExposeProvenance, _, _) => {
@@ -458,10 +462,6 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                 // Since no pointer can ever get exposed (rejected above), this is easy to support.
             }
 
-            Rvalue::Cast(CastKind::DynStar, _, _) => {
-                // `dyn*` coercion is implemented for CTFE.
-            }
-
             Rvalue::Cast(_, _, _) => {}
 
             Rvalue::NullaryOp(
diff --git a/compiler/rustc_const_eval/src/interpret/cast.rs b/compiler/rustc_const_eval/src/interpret/cast.rs
@@ -125,7 +125,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                 }
             }
 
-            CastKind::DynStar => {
+            CastKind::PointerCoercion(PointerCoercion::DynStar) => {
                 if let ty::Dynamic(data, _, ty::DynStar) = cast_ty.kind() {
                     // Initial cast from sized to dyn trait
                     let vtable = self.get_vtable_ptr(src.layout.ty, data.principal())?;
diff --git a/compiler/rustc_hir_typeck/src/cast.rs b/compiler/rustc_hir_typeck/src/cast.rs
@@ -33,12 +33,12 @@ use rustc_errors::codes::*;
 use rustc_errors::{Applicability, Diag, ErrorGuaranteed};
 use rustc_hir::{self as hir, ExprKind};
 use rustc_macros::{TypeFoldable, TypeVisitable};
-use rustc_middle::bug;
 use rustc_middle::mir::Mutability;
 use rustc_middle::ty::adjustment::AllowTwoPhase;
 use rustc_middle::ty::cast::{CastKind, CastTy};
 use rustc_middle::ty::error::TypeError;
 use rustc_middle::ty::{self, Ty, TyCtxt, TypeAndMut, TypeVisitableExt, VariantDef};
+use rustc_middle::{bug, span_bug};
 use rustc_session::lint;
 use rustc_span::def_id::LOCAL_CRATE;
 use rustc_span::symbol::sym;
@@ -678,6 +678,16 @@ impl<'a, 'tcx> CastCheck<'tcx> {
         use rustc_middle::ty::cast::CastTy::*;
         use rustc_middle::ty::cast::IntTy::*;
 
+        if self.cast_ty.is_dyn_star() {
+            if fcx.tcx.features().dyn_star {
+                span_bug!(self.span, "should be handled by `coerce`");
+            } else {
+                // Report "casting is invalid" rather than "non-primitive cast"
+                // if the feature is not enabled.
+                return Err(CastError::IllegalCast);
+            }
+        }
+
         let (t_from, t_cast) = match (CastTy::from_ty(self.expr_ty), CastTy::from_ty(self.cast_ty))
         {
             (Some(t_from), Some(t_cast)) => (t_from, t_cast),
@@ -784,16 +794,6 @@ impl<'a, 'tcx> CastCheck<'tcx> {
             (Int(Char) | Int(Bool), Int(_)) => Ok(CastKind::PrimIntCast),
 
             (Int(_) | Float, Int(_) | Float) => Ok(CastKind::NumericCast),
-
-            (_, DynStar) => {
-                if fcx.tcx.features().dyn_star {
-                    bug!("should be handled by `coerce`")
-                } else {
-                    Err(CastError::IllegalCast)
-                }
-            }
-
-            (DynStar, _) => Err(CastError::IllegalCast),
         }
     }
 
diff --git a/compiler/rustc_hir_typeck/src/coercion.rs b/compiler/rustc_hir_typeck/src/coercion.rs
@@ -769,7 +769,10 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
         ));
 
         Ok(InferOk {
-            value: (vec![Adjustment { kind: Adjust::DynStar, target: b }], b),
+            value: (
+                vec![Adjustment { kind: Adjust::Pointer(PointerCoercion::DynStar), target: b }],
+                b,
+            ),
             obligations,
         })
     }
diff --git a/compiler/rustc_hir_typeck/src/expr_use_visitor.rs b/compiler/rustc_hir_typeck/src/expr_use_visitor.rs
@@ -757,9 +757,7 @@ impl<'tcx, Cx: TypeInformationCtxt<'tcx>, D: Delegate<'tcx>> ExprUseVisitor<'tcx
         for adjustment in adjustments {
             debug!("walk_adjustment expr={:?} adj={:?}", expr, adjustment);
             match adjustment.kind {
-                adjustment::Adjust::NeverToAny
-                | adjustment::Adjust::Pointer(_)
-                | adjustment::Adjust::DynStar => {
+                adjustment::Adjust::NeverToAny | adjustment::Adjust::Pointer(_) => {
                     // Creating a closure/fn-pointer or unsizing consumes
                     // the input and stores it into the resulting rvalue.
                     self.consume_or_copy(&place_with_id, place_with_id.hir_id);
@@ -1283,8 +1281,7 @@ impl<'tcx, Cx: TypeInformationCtxt<'tcx>, D: Delegate<'tcx>> ExprUseVisitor<'tcx
 
             adjustment::Adjust::NeverToAny
             | adjustment::Adjust::Pointer(_)
-            | adjustment::Adjust::Borrow(_)
-            | adjustment::Adjust::DynStar => {
+            | adjustment::Adjust::Borrow(_) => {
                 // Result is an rvalue.
                 Ok(self.cat_rvalue(expr.hir_id, target))
             }
diff --git a/compiler/rustc_middle/src/mir/statement.rs b/compiler/rustc_middle/src/mir/statement.rs
@@ -434,7 +434,6 @@ impl<'tcx> Rvalue<'tcx> {
                 | CastKind::PtrToPtr
                 | CastKind::PointerCoercion(_)
                 | CastKind::PointerWithExposedProvenance
-                | CastKind::DynStar
                 | CastKind::Transmute,
                 _,
                 _,
diff --git a/compiler/rustc_middle/src/mir/syntax.rs b/compiler/rustc_middle/src/mir/syntax.rs
@@ -1404,8 +1404,6 @@ pub enum CastKind {
     ///
     /// Both are runtime nops, so should be [`CastKind::PtrToPtr`] instead in runtime MIR.
     PointerCoercion(PointerCoercion),
-    /// Cast into a dyn* object.
-    DynStar,
     IntToInt,
     FloatToInt,
     FloatToFloat,
diff --git a/compiler/rustc_middle/src/ty/adjustment.rs b/compiler/rustc_middle/src/ty/adjustment.rs
@@ -35,6 +35,9 @@ pub enum PointerCoercion {
     /// type. Codegen backends and miri figure out what has to be done
     /// based on the precise source/target type at hand.
     Unsize,
+
+    /// Go from a pointer-like type to a `dyn*` object.
+    DynStar,
 }
 
 /// Represents coercing a value to a different type of value.
@@ -101,9 +104,6 @@ pub enum Adjust<'tcx> {
     Borrow(AutoBorrow<'tcx>),
 
     Pointer(PointerCoercion),
-
-    /// Cast into a dyn* object.
-    DynStar,
 }
 
 /// An overloaded autoderef step, representing a `Deref(Mut)::deref(_mut)`
diff --git a/compiler/rustc_middle/src/ty/cast.rs b/compiler/rustc_middle/src/ty/cast.rs
@@ -34,15 +34,12 @@ pub enum CastTy<'tcx> {
     FnPtr,
     /// Raw pointers.
     Ptr(ty::TypeAndMut<'tcx>),
-    /// Casting into a `dyn*` value.
-    DynStar,
 }
 
 /// Cast Kind. See [RFC 401](https://rust-lang.github.io/rfcs/0401-coercions.html)
 /// (or rustc_hir_analysis/check/cast.rs).
 #[derive(Copy, Clone, Debug, TyEncodable, TyDecodable, HashStable)]
 pub enum CastKind {
-    CoercionCast,
     PtrPtrCast,
     PtrAddrCast,
     AddrPtrCast,
@@ -53,7 +50,6 @@ pub enum CastKind {
     ArrayPtrCast,
     FnPtrPtrCast,
     FnPtrAddrCast,
-    DynStarCast,
 }
 
 impl<'tcx> CastTy<'tcx> {
@@ -71,7 +67,6 @@ impl<'tcx> CastTy<'tcx> {
             ty::Adt(d, _) if d.is_enum() && d.is_payloadfree() => Some(CastTy::Int(IntTy::CEnum)),
             ty::RawPtr(ty, mutbl) => Some(CastTy::Ptr(ty::TypeAndMut { ty, mutbl })),
             ty::FnPtr(..) => Some(CastTy::FnPtr),
-            ty::Dynamic(_, _, ty::DynStar) => Some(CastTy::DynStar),
             _ => None,
         }
     }
@@ -86,7 +81,6 @@ pub fn mir_cast_kind<'tcx>(from_ty: Ty<'tcx>, cast_ty: Ty<'tcx>) -> mir::CastKin
             mir::CastKind::PointerExposeProvenance
         }
         (Some(CastTy::Int(_)), Some(CastTy::Ptr(_))) => mir::CastKind::PointerWithExposedProvenance,
-        (_, Some(CastTy::DynStar)) => mir::CastKind::DynStar,
         (Some(CastTy::Int(_)), Some(CastTy::Int(_))) => mir::CastKind::IntToInt,
         (Some(CastTy::FnPtr), Some(CastTy::Ptr(_))) => mir::CastKind::FnPtrToPtr,
 
diff --git a/compiler/rustc_mir_build/src/thir/cx/expr.rs b/compiler/rustc_mir_build/src/thir/cx/expr.rs
@@ -145,7 +145,6 @@ impl<'tcx> Cx<'tcx> {
             Adjust::Borrow(AutoBorrow::RawPtr(mutability)) => {
                 ExprKind::RawBorrow { mutability, arg: self.thir.exprs.push(expr) }
             }
-            Adjust::DynStar => ExprKind::Cast { source: self.thir.exprs.push(expr) },
         };
 
         Expr { temp_lifetime, ty: adjustment.target, span, kind }
diff --git a/compiler/rustc_mir_transform/src/mentioned_items.rs b/compiler/rustc_mir_transform/src/mentioned_items.rs
@@ -70,11 +70,11 @@ impl<'tcx> Visitor<'tcx> for MentionedItemsVisitor<'_, 'tcx> {
         match *rvalue {
             // We need to detect unsizing casts that required vtables.
             mir::Rvalue::Cast(
-                mir::CastKind::PointerCoercion(PointerCoercion::Unsize),
+                mir::CastKind::PointerCoercion(PointerCoercion::Unsize)
+                | mir::CastKind::PointerCoercion(PointerCoercion::DynStar),
                 ref operand,
                 target_ty,
-            )
-            | mir::Rvalue::Cast(mir::CastKind::DynStar, ref operand, target_ty) => {
+            ) => {
                 // This isn't monomorphized yet so we can't tell what the actual types are -- just
                 // add everything that may involve a vtable.
                 let source_ty = operand.ty(self.body, self.tcx);
diff --git a/compiler/rustc_mir_transform/src/validate.rs b/compiler/rustc_mir_transform/src/validate.rs
@@ -1128,9 +1128,6 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
             Rvalue::Cast(kind, operand, target_type) => {
                 let op_ty = operand.ty(self.body, self.tcx);
                 match kind {
-                    CastKind::DynStar => {
-                        // FIXME(dyn-star): make sure nothing needs to be done here.
-                    }
                     // FIXME: Add Checks for these
                     CastKind::PointerWithExposedProvenance | CastKind::PointerExposeProvenance => {}
                     CastKind::PointerCoercion(PointerCoercion::ReifyFnPointer) => {
@@ -1208,6 +1205,9 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                         // This is used for all `CoerceUnsized` types,
                         // not just pointers/references, so is hard to check.
                     }
+                    CastKind::PointerCoercion(PointerCoercion::DynStar) => {
+                        // FIXME(dyn-star): make sure nothing needs to be done here.
+                    }
                     CastKind::IntToInt | CastKind::IntToFloat => {
                         let input_valid = op_ty.is_integral() || op_ty.is_char() || op_ty.is_bool();
                         let target_valid = target_type.is_numeric() || target_type.is_char();
diff --git a/compiler/rustc_monomorphize/src/collector.rs b/compiler/rustc_monomorphize/src/collector.rs
@@ -665,11 +665,11 @@ impl<'a, 'tcx> MirVisitor<'tcx> for MirUsedCollector<'a, 'tcx> {
             // have to instantiate all methods of the trait being cast to, so we
             // can build the appropriate vtable.
             mir::Rvalue::Cast(
-                mir::CastKind::PointerCoercion(PointerCoercion::Unsize),
+                mir::CastKind::PointerCoercion(PointerCoercion::Unsize)
+                | mir::CastKind::PointerCoercion(PointerCoercion::DynStar),
                 ref operand,
                 target_ty,
-            )
-            | mir::Rvalue::Cast(mir::CastKind::DynStar, ref operand, target_ty) => {
+            ) => {
                 let source_ty = operand.ty(self.body, self.tcx);
                 // *Before* monomorphizing, record that we already handled this mention.
                 self.used_mentioned_items
diff --git a/compiler/rustc_smir/src/rustc_smir/convert/mir.rs b/compiler/rustc_smir/src/rustc_smir/convert/mir.rs
@@ -282,11 +282,12 @@ impl<'tcx> Stable<'tcx> for mir::CastKind {
     type T = stable_mir::mir::CastKind;
     fn stable(&self, tables: &mut Tables<'_>) -> Self::T {
         use rustc_middle::mir::CastKind::*;
+        use rustc_middle::ty::adjustment::PointerCoercion;
         match self {
             PointerExposeProvenance => stable_mir::mir::CastKind::PointerExposeAddress,
             PointerWithExposedProvenance => stable_mir::mir::CastKind::PointerWithExposedProvenance,
+            PointerCoercion(PointerCoercion::DynStar) => stable_mir::mir::CastKind::DynStar,
             PointerCoercion(c) => stable_mir::mir::CastKind::PointerCoercion(c.stable(tables)),
-            DynStar => stable_mir::mir::CastKind::DynStar,
             IntToInt => stable_mir::mir::CastKind::IntToInt,
             FloatToInt => stable_mir::mir::CastKind::FloatToInt,
             FloatToFloat => stable_mir::mir::CastKind::FloatToFloat,
diff --git a/compiler/rustc_smir/src/rustc_smir/convert/ty.rs b/compiler/rustc_smir/src/rustc_smir/convert/ty.rs
@@ -119,6 +119,7 @@ impl<'tcx> Stable<'tcx> for ty::adjustment::PointerCoercion {
             }
             PointerCoercion::ArrayToPointer => stable_mir::mir::PointerCoercion::ArrayToPointer,
             PointerCoercion::Unsize => stable_mir::mir::PointerCoercion::Unsize,
+            PointerCoercion::DynStar => unreachable!("represented as `CastKind::DynStar` in smir"),
         }
     }
 }
diff --git a/compiler/stable_mir/src/mir/body.rs b/compiler/stable_mir/src/mir/body.rs
@@ -960,6 +960,7 @@ pub enum CastKind {
     PointerExposeAddress,
     PointerWithExposedProvenance,
     PointerCoercion(PointerCoercion),
+    // FIXME(smir-rename): change this to PointerCoercion(DynStar)
     DynStar,
     IntToInt,
     FloatToInt,
diff --git a/src/tools/clippy/clippy_utils/src/qualify_min_const_fn.rs b/src/tools/clippy/clippy_utils/src/qualify_min_const_fn.rs
@@ -154,7 +154,7 @@ fn check_rvalue<'tcx>(
         Rvalue::Cast(CastKind::PointerExposeProvenance, _, _) => {
             Err((span, "casting pointers to ints is unstable in const fn".into()))
         },
-        Rvalue::Cast(CastKind::DynStar, _, _) => {
+        Rvalue::Cast(CastKind::PointerCoercion(PointerCoercion::DynStar), _, _) => {
             // FIXME(dyn-star)
             unimplemented!()
         },
diff --git a/tests/ui/dyn-star/dyn-to-rigid.rs b/tests/ui/dyn-star/dyn-to-rigid.rs
@@ -5,7 +5,7 @@ trait Tr {}
 
 fn f(x: dyn* Tr) -> usize {
     x as usize
-    //~^ ERROR casting `(dyn* Tr + 'static)` as `usize` is invalid
+    //~^ ERROR non-primitive cast: `(dyn* Tr + 'static)` as `usize`
 }
 
 fn main() {}
diff --git a/tests/ui/dyn-star/dyn-to-rigid.stderr b/tests/ui/dyn-star/dyn-to-rigid.stderr
@@ -1,9 +1,9 @@
-error[E0606]: casting `(dyn* Tr + 'static)` as `usize` is invalid
+error[E0605]: non-primitive cast: `(dyn* Tr + 'static)` as `usize`
   --> $DIR/dyn-to-rigid.rs:7:5
    |
 LL |     x as usize
-   |     ^^^^^^^^^^
+   |     ^^^^^^^^^^ an `as` expression can only be used to convert between primitive types or to coerce to a specific trait object
 
 error: aborting due to 1 previous error
 
-For more information about this error, try `rustc --explain E0606`.
+For more information about this error, try `rustc --explain E0605`.
diff --git a/tests/ui/dyn-star/enum-cast.rs b/tests/ui/dyn-star/enum-cast.rs
@@ -0,0 +1,18 @@
+//@ check-pass
+
+// This used to ICE, because the compiler confused a pointer-like to dyn* coercion
+// with a c-like enum to integer cast.
+
+#![feature(dyn_star)]
+#![expect(incomplete_features)]
+
+enum E {
+    Num(usize),
+}
+
+trait Trait {}
+impl Trait for E {}
+
+fn main() {
+    let _ = E::Num(42) as dyn* Trait;
+}

Original file line number	Diff line number	Diff line change
`@@ -2141,7 +2141,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {`
`2141`	`2141`	`);`
`2142`	`2142`	`}`
`2143`	`2143`
`2144`		`- CastKind::DynStar => {`
	`2144`	`+ CastKind::PointerCoercion(PointerCoercion::DynStar) => {`
`2145`	`2145`	// get the constraints from the target type (`dyn* Clone`)
`2146`	`2146`	`//`
`2147`	`2147`	// apply them to prove that the source type `Foo` implements `Clone` etc
Original file line number	Diff line number	Diff line change
`@@ -770,7 +770,11 @@ fn codegen_stmt<'tcx>(`
`770`	`770`	`let operand = codegen_operand(fx, operand);`
`771`	`771`	`crate::unsize::coerce_unsized_into(fx, operand, lval);`
`772`	`772`	`}`
`773`		`- Rvalue::Cast(CastKind::DynStar, ref operand, _) => {`
	`773`	`+ Rvalue::Cast(`
	`774`	`+ CastKind::PointerCoercion(PointerCoercion::DynStar),`
	`775`	`+ ref operand,`
	`776`	`+ _,`
	`777`	`+ ) => {`
`774`	`778`	`let operand = codegen_operand(fx, operand);`
`775`	`779`	`crate::unsize::coerce_dyn_star(fx, operand, lval);`
`776`	`780`	`}`
Original file line number	Diff line number	Diff line change
`@@ -525,7 +525,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {`
`525`	`525`	`bug!("unexpected non-pair operand");`
`526`	`526`	`}`
`527`	`527`	`}`
`528`		`- mir::CastKind::DynStar => {`
	`528`	`+ mir::CastKind::PointerCoercion(PointerCoercion::DynStar) => {`
`529`	`529`	`let (lldata, llextra) = operand.val.pointer_parts();`
`530`	`530`	`let (lldata, llextra) =`
`531`	`531`	`base::cast_to_dyn_star(bx, lldata, operand.layout, cast.ty, llextra);`
Original file line number	Diff line number	Diff line change
`@@ -125,7 +125,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {`
`125`	`125`	`}`
`126`	`126`	`}`
`127`	`127`
`128`		`- CastKind::DynStar => {`
	`128`	`+ CastKind::PointerCoercion(PointerCoercion::DynStar) => {`
`129`	`129`	`if let ty::Dynamic(data, _, ty::DynStar) = cast_ty.kind() {`
`130`	`130`	`// Initial cast from sized to dyn trait`
`131`	`131`	`let vtable = self.get_vtable_ptr(src.layout.ty, data.principal())?;`