miri: for ABI mismatch errors, say which argument is the problem

compiler/rustc_const_eval/messages.ftl

@@ -128,15 +128,15 @@ const_eval_frame_note_inner = inside {$where_ ->
 
 const_eval_frame_note_last = the failure occurred here
 
+const_eval_incompatible_arg_types =
+    calling a function whose parameter #{$arg_idx} has type {$callee_ty} passing argument of type {$caller_ty}
+
 const_eval_incompatible_calling_conventions =
     calling a function with calling convention "{$callee_conv}" using calling convention "{$caller_conv}"
 
 const_eval_incompatible_return_types =
     calling a function with return type {$callee_ty} passing return place of type {$caller_ty}
 
-const_eval_incompatible_types =
-    calling a function with argument of type {$callee_ty} passing data of type {$caller_ty}
-
 const_eval_interior_mutable_borrow_escaping =
     interior mutable shared borrows of temporaries that have their lifetime extended until the end of the program are not allowed
     .label = this borrow of an interior mutable value refers to such a temporary

compiler/rustc_const_eval/src/errors.rs

@@ -500,7 +500,7 @@ impl<'a> ReportErrorExt for UndefinedBehaviorInfo<'a> {
             InvalidNichedEnumVariantWritten { .. } => {
                 const_eval_invalid_niched_enum_variant_written
             }
-            AbiMismatchArgument { .. } => const_eval_incompatible_types,
+            AbiMismatchArgument { .. } => const_eval_incompatible_arg_types,
             AbiMismatchReturn { .. } => const_eval_incompatible_return_types,
         }
     }
@@ -625,12 +625,16 @@ impl<'a> ReportErrorExt for UndefinedBehaviorInfo<'a> {
                 diag.arg("data_size", info.data_size);
             }
             InvalidNichedEnumVariantWritten { enum_ty } => {
-                diag.arg("ty", enum_ty.to_string());
+                diag.arg("ty", enum_ty);
             }
-            AbiMismatchArgument { caller_ty, callee_ty }
-            | AbiMismatchReturn { caller_ty, callee_ty } => {
-                diag.arg("caller_ty", caller_ty.to_string());
-                diag.arg("callee_ty", callee_ty.to_string());
+            AbiMismatchArgument { arg_idx, caller_ty, callee_ty } => {
+                diag.arg("arg_idx", arg_idx + 1); // adjust for 1-indexed lists in output
+                diag.arg("caller_ty", caller_ty);
+                diag.arg("callee_ty", callee_ty);
+            }
+            AbiMismatchReturn { caller_ty, callee_ty } => {
+                diag.arg("caller_ty", caller_ty);
+                diag.arg("callee_ty", callee_ty);
             }
         }
     }

compiler/rustc_const_eval/src/interpret/call.rs

@@ -270,6 +270,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
             Item = (&'x FnArg<'tcx, M::Provenance>, &'y ArgAbi<'tcx, Ty<'tcx>>),
         >,
         callee_abi: &ArgAbi<'tcx, Ty<'tcx>>,
+        callee_arg_idx: usize,
         callee_arg: &mir::Place<'tcx>,
         callee_ty: Ty<'tcx>,
         already_live: bool,
@@ -298,6 +299,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         // Check compatibility
         if !self.check_argument_compat(caller_abi, callee_abi)? {
             throw_ub!(AbiMismatchArgument {
+                arg_idx: callee_arg_idx,
                 caller_ty: caller_abi.layout.ty,
                 callee_ty: callee_abi.layout.ty
             });
@@ -424,7 +426,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
             // this is a single iterator (that handles `spread_arg`), then
             // `pass_argument` would be the loop body. It takes care to
             // not advance `caller_iter` for ignored arguments.
-            let mut callee_args_abis = callee_fn_abi.args.iter();
+            let mut callee_args_abis = callee_fn_abi.args.iter().enumerate();
             for local in body.args_iter() {
                 // Construct the destination place for this argument. At this point all
                 // locals are still dead, so we cannot construct a `PlaceTy`.
@@ -445,21 +447,23 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                             &[mir::ProjectionElem::Field(FieldIdx::from_usize(i), field_ty)],
                             *self.tcx,
                         );
-                        let callee_abi = callee_args_abis.next().unwrap();
+                        let (idx, callee_abi) = callee_args_abis.next().unwrap();
                         self.pass_argument(
                             &mut caller_args,
                             callee_abi,
+                            idx,
                             &dest,
                             field_ty,
                             /* already_live */ true,
                         )?;
                     }
                 } else {
                     // Normal argument. Cannot mark it as live yet, it might be unsized!
-                    let callee_abi = callee_args_abis.next().unwrap();
+                    let (idx, callee_abi) = callee_args_abis.next().unwrap();
                     self.pass_argument(
                         &mut caller_args,
                         callee_abi,
+                        idx,
                         &dest,
                         ty,
                         /* already_live */ false,

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

@@ -426,7 +426,12 @@ pub enum UndefinedBehaviorInfo<'tcx> {
     /// Trying to set discriminant to the niched variant, but the value does not match.
     InvalidNichedEnumVariantWritten { enum_ty: Ty<'tcx> },
     /// ABI-incompatible argument types.
-    AbiMismatchArgument { caller_ty: Ty<'tcx>, callee_ty: Ty<'tcx> },
+    AbiMismatchArgument {
+        /// The index of the argument whose type is wrong.
+        arg_idx: usize,
+        caller_ty: Ty<'tcx>,
+        callee_ty: Ty<'tcx>,
+    },
     /// ABI-incompatible return types.
     AbiMismatchReturn { caller_ty: Ty<'tcx>, callee_ty: Ty<'tcx> },
 }

src/tools/miri/src/diagnostics.rs

@@ -382,7 +382,7 @@ pub fn report_error<'tcx>(
                             helps.push(note_span!(span, "{:?} was deallocated here:", alloc_id));
                         }
                     }
-                    AbiMismatchArgument { .. } | AbiMismatchReturn { .. } => {
+                    AbiMismatchArgument { .. } => {
                         helps.push(note!("this means these two types are not *guaranteed* to be ABI-compatible across all targets"));
                         helps.push(note!("if you think this code should be accepted anyway, please report an issue with Miri"));
                     }

src/tools/miri/src/helpers.rs

@@ -1079,6 +1079,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
             .position(|b| !b)
         {
             throw_ub!(AbiMismatchArgument {
+                arg_idx: index,
                 caller_ty: caller_fn_abi.args[index].layout.ty,
                 callee_ty: callee_fn_abi.args[index].layout.ty
             });

src/tools/miri/tests/fail/function_pointers/abi_mismatch_array_vs_struct.rs

@@ -17,5 +17,5 @@ fn main() {
     // These two types have the same size but are still not compatible.
     let g = unsafe { std::mem::transmute::<fn(S), fn(A)>(f) };
 
-    g(Default::default()) //~ ERROR: calling a function with argument of type S passing data of type [i32; 4]
+    g(Default::default()) //~ ERROR: type S passing argument of type [i32; 4]
 }

src/tools/miri/tests/fail/function_pointers/abi_mismatch_array_vs_struct.stderr

@@ -1,4 +1,4 @@
-error: Undefined Behavior: calling a function with argument of type S passing data of type [i32; 4]
+error: Undefined Behavior: calling a function whose parameter #1 has type S passing argument of type [i32; 4]
   --> tests/fail/function_pointers/abi_mismatch_array_vs_struct.rs:LL:CC
    |
 LL |     g(Default::default())

src/tools/miri/tests/fail/function_pointers/abi_mismatch_int_vs_float.rs

@@ -3,5 +3,5 @@ fn main() {
 
     let g = unsafe { std::mem::transmute::<fn(f32), fn(i32)>(f) };
 
-    g(42) //~ ERROR: calling a function with argument of type f32 passing data of type i32
+    g(42) //~ ERROR: type f32 passing argument of type i32
 }

src/tools/miri/tests/fail/function_pointers/abi_mismatch_int_vs_float.stderr

@@ -1,4 +1,4 @@
-error: Undefined Behavior: calling a function with argument of type f32 passing data of type i32
+error: Undefined Behavior: calling a function whose parameter #1 has type f32 passing argument of type i32
   --> tests/fail/function_pointers/abi_mismatch_int_vs_float.rs:LL:CC
    |
 LL |     g(42)

src/tools/miri/tests/fail/function_pointers/abi_mismatch_raw_pointer.rs

@@ -3,5 +3,5 @@ fn main() {
 
     let g = unsafe { std::mem::transmute::<fn(*const [i32]), fn(*const i32)>(f) };
 
-    g(&42 as *const i32) //~ ERROR: calling a function with argument of type *const [i32] passing data of type *const i32
+    g(&42 as *const i32) //~ ERROR: type *const [i32] passing argument of type *const i32
 }

src/tools/miri/tests/fail/function_pointers/abi_mismatch_raw_pointer.stderr

@@ -1,4 +1,4 @@
-error: Undefined Behavior: calling a function with argument of type *const [i32] passing data of type *const i32
+error: Undefined Behavior: calling a function whose parameter #1 has type *const [i32] passing argument of type *const i32
   --> tests/fail/function_pointers/abi_mismatch_raw_pointer.rs:LL:CC
    |
 LL |     g(&42 as *const i32)

src/tools/miri/tests/fail/function_pointers/abi_mismatch_repr_C.rs

@@ -12,5 +12,5 @@ fn main() {
     let fnptr: fn(S2) = callee;
     let fnptr: fn(S1) = unsafe { std::mem::transmute(fnptr) };
     fnptr(S1(NonZero::new(1).unwrap()));
-    //~^ ERROR: calling a function with argument of type S2 passing data of type S1
+    //~^ ERROR: type S2 passing argument of type S1
 }

src/tools/miri/tests/fail/function_pointers/abi_mismatch_repr_C.stderr

@@ -1,4 +1,4 @@
-error: Undefined Behavior: calling a function with argument of type S2 passing data of type S1
+error: Undefined Behavior: calling a function whose parameter #1 has type S2 passing argument of type S1
   --> tests/fail/function_pointers/abi_mismatch_repr_C.rs:LL:CC
    |
 LL |     fnptr(S1(NonZero::new(1).unwrap()));

src/tools/miri/tests/fail/function_pointers/abi_mismatch_return_type.rs

@@ -5,5 +5,5 @@ fn main() {
 
     let g = unsafe { std::mem::transmute::<fn() -> u32, fn()>(f) };
 
-    g() //~ ERROR: calling a function with return type u32 passing return place of type ()
+    g() //~ ERROR: type u32 passing return place of type ()
 }

src/tools/miri/tests/fail/function_pointers/abi_mismatch_return_type.stderr

@@ -6,8 +6,6 @@ LL |     g()
    |
    = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
    = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
-   = help: this means these two types are not *guaranteed* to be ABI-compatible across all targets
-   = help: if you think this code should be accepted anyway, please report an issue with Miri
    = note: BACKTRACE:
    = note: inside `main` at tests/fail/function_pointers/abi_mismatch_return_type.rs:LL:CC
 

src/tools/miri/tests/fail/function_pointers/abi_mismatch_simple.rs

@@ -3,5 +3,5 @@ fn main() {
 
     let g = unsafe { std::mem::transmute::<fn((i32, i32)), fn(i32)>(f) };
 
-    g(42) //~ ERROR: calling a function with argument of type (i32, i32) passing data of type i32
+    g(42) //~ ERROR: type (i32, i32) passing argument of type i32
 }

src/tools/miri/tests/fail/function_pointers/abi_mismatch_simple.stderr

@@ -1,4 +1,4 @@
-error: Undefined Behavior: calling a function with argument of type (i32, i32) passing data of type i32
+error: Undefined Behavior: calling a function whose parameter #1 has type (i32, i32) passing argument of type i32
   --> tests/fail/function_pointers/abi_mismatch_simple.rs:LL:CC
    |
 LL |     g(42)

src/tools/miri/tests/fail/function_pointers/abi_mismatch_vector.rs

@@ -7,5 +7,5 @@ fn main() {
     // These two vector types have the same size but are still not compatible.
     let g = unsafe { std::mem::transmute::<fn(simd::u32x8), fn(simd::u64x4)>(f) };
 
-    g(Default::default()) //~ ERROR: calling a function with argument of type std::simd::Simd<u32, 8> passing data of type std::simd::Simd<u64, 4>
+    g(Default::default()) //~ ERROR: type std::simd::Simd<u32, 8> passing argument of type std::simd::Simd<u64, 4>
 }

src/tools/miri/tests/fail/function_pointers/abi_mismatch_vector.stderr

@@ -1,4 +1,4 @@
-error: Undefined Behavior: calling a function with argument of type std::simd::Simd<u32, 8> passing data of type std::simd::Simd<u64, 4>
+error: Undefined Behavior: calling a function whose parameter #1 has type std::simd::Simd<u32, 8> passing argument of type std::simd::Simd<u64, 4>
   --> tests/fail/function_pointers/abi_mismatch_vector.rs:LL:CC
    |
 LL |     g(Default::default())

src/tools/miri/tests/fail/shims/input_arg_mismatch.rs

@@ -16,6 +16,6 @@ fn main() {
     } as u32;
     let _ = unsafe {
         close(fd);
-        //~^ ERROR: calling a function with argument of type i32 passing data of type u32
+        //~^ ERROR: type i32 passing argument of type u32
     };
 }

src/tools/miri/tests/fail/shims/input_arg_mismatch.stderr

@@ -1,4 +1,4 @@
-error: Undefined Behavior: calling a function with argument of type i32 passing data of type u32
+error: Undefined Behavior: calling a function whose parameter #1 has type i32 passing argument of type u32
   --> tests/fail/shims/input_arg_mismatch.rs:LL:CC
    |
 LL |         close(fd);

src/tools/miri/tests/fail/shims/return_type_mismatch.stderr

@@ -6,8 +6,6 @@ LL |         close(fd);
    |
    = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
    = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
-   = help: this means these two types are not *guaranteed* to be ABI-compatible across all targets
-   = help: if you think this code should be accepted anyway, please report an issue with Miri
    = note: BACKTRACE:
    = note: inside `main` at tests/fail/shims/return_type_mismatch.rs:LL:CC
 

src/tools/miri/tests/fail/tail_calls/signature-mismatch-arg.rs

@@ -6,7 +6,7 @@ fn main() {
     //   the error should point to `become g(x)`,
     //   but tail calls mess up the backtrace it seems like...
     f(0);
-    //~^ error: Undefined Behavior: calling a function with argument of type i32 passing data of type u32
+    //~^ error: type i32 passing argument of type u32
 }
 
 fn f(x: u32) {

src/tools/miri/tests/fail/tail_calls/signature-mismatch-arg.stderr

@@ -1,4 +1,4 @@
-error: Undefined Behavior: calling a function with argument of type i32 passing data of type u32
+error: Undefined Behavior: calling a function whose parameter #1 has type i32 passing argument of type u32
   --> tests/fail/tail_calls/signature-mismatch-arg.rs:LL:CC
    |
 LL |     f(0);