[tests] add transmute! UI tests (#456)

These tests are split into distinct files, so that changes to
`transmute!` can be more easily carefully and incrementally
reviewed.

.github/workflows/ci.yml

@@ -162,7 +162,10 @@ jobs:
           --package ${{ matrix.crate }} \
           --target ${{ matrix.target }} \
           ${{ matrix.features }} \
-          --verbose
+          --verbose \
+          -- \
+          ${{ (matrix.features == '--no-default-features' || matrix.features == '') &&  '--skip ui' || '' }} \
+
       # Only run tests when targetting x86 (32- or 64-bit) - we're executing on
       # x86_64, so we can't run tests for any non-x86 target.
       #

tests/ui-msrv/transmute-dst-not-frombytes.rs

@@ -0,0 +1 @@
+../ui-nightly/transmute-dst-not-frombytes.rs

tests/ui-msrv/transmute-dst-not-frombytes.stderr

@@ -0,0 +1,12 @@
+error[E0277]: the trait bound `NotZerocopy: FromBytes` is not satisfied
+  --> tests/ui-msrv/transmute-dst-not-frombytes.rs:14:41
+   |
+14 | const DST_NOT_FROM_BYTES: NotZerocopy = transmute!(AU16(0));
+   |                                         ^^^^^^^^^^^^^^^^^^^ the trait `FromBytes` is not implemented for `NotZerocopy`
+   |
+note: required by a bound in `DST_NOT_FROM_BYTES::transmute`
+  --> tests/ui-msrv/transmute-dst-not-frombytes.rs:14:41
+   |
+14 | const DST_NOT_FROM_BYTES: NotZerocopy = transmute!(AU16(0));
+   |                                         ^^^^^^^^^^^^^^^^^^^ required by this bound in `DST_NOT_FROM_BYTES::transmute`
+   = note: this error originates in the macro `transmute` (in Nightly builds, run with -Z macro-backtrace for more info)

tests/ui-msrv/transmute-ptr-to-usize.rs

@@ -0,0 +1 @@
+../ui-nightly/transmute-ptr-to-usize.rs

tests/ui-msrv/transmute-ptr-to-usize.stderr

@@ -0,0 +1,18 @@
+error[E0277]: the trait bound `*const usize: AsBytes` is not satisfied
+  --> tests/ui-msrv/transmute-ptr-to-usize.rs:16:30
+   |
+16 | const POINTER_VALUE: usize = transmute!(&0usize as *const usize);
+   |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `AsBytes` is not implemented for `*const usize`
+   |
+   = help: the following implementations were found:
+             <usize as AsBytes>
+             <f32 as AsBytes>
+             <f64 as AsBytes>
+             <i128 as AsBytes>
+           and $N others
+note: required by a bound in `POINTER_VALUE::transmute`
+  --> tests/ui-msrv/transmute-ptr-to-usize.rs:16:30
+   |
+16 | const POINTER_VALUE: usize = transmute!(&0usize as *const usize);
+   |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `POINTER_VALUE::transmute`
+   = note: this error originates in the macro `transmute` (in Nightly builds, run with -Z macro-backtrace for more info)

tests/ui-msrv/transmute-size-decrease.rs

@@ -0,0 +1 @@
+../ui-nightly/transmute-size-decrease.rs

tests/ui-msrv/transmute-size-decrease.stderr

@@ -0,0 +1,9 @@
+error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
+  --> tests/ui-msrv/transmute-size-decrease.rs:15:27
+   |
+15 | const DECREASE_SIZE: u8 = transmute!(AU16(0));
+   |                           ^^^^^^^^^^^^^^^^^^^
+   |
+   = note: source type: `AU16` (16 bits)
+   = note: target type: `u8` (8 bits)
+   = note: this error originates in the macro `transmute` (in Nightly builds, run with -Z macro-backtrace for more info)

tests/ui-msrv/transmute-size-increase.rs

@@ -0,0 +1 @@
+../ui-nightly/transmute-size-increase.rs

tests/ui-msrv/transmute-size-increase.stderr

@@ -0,0 +1,9 @@
+error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
+  --> tests/ui-msrv/transmute-size-increase.rs:15:29
+   |
+15 | const INCREASE_SIZE: AU16 = transmute!(0u8);
+   |                             ^^^^^^^^^^^^^^^
+   |
+   = note: source type: `u8` (8 bits)
+   = note: target type: `AU16` (16 bits)
+   = note: this error originates in the macro `transmute` (in Nightly builds, run with -Z macro-backtrace for more info)

tests/ui-msrv/transmute-src-not-asbytes.rs

@@ -0,0 +1 @@
+../ui-nightly/transmute-src-not-asbytes.rs

tests/ui-msrv/transmute-src-not-asbytes.stderr

@@ -0,0 +1,12 @@
+error[E0277]: the trait bound `NotZerocopy<AU16>: AsBytes` is not satisfied
+  --> tests/ui-msrv/transmute-src-not-asbytes.rs:14:32
+   |
+14 | const SRC_NOT_AS_BYTES: AU16 = transmute!(NotZerocopy(AU16(0)));
+   |                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `AsBytes` is not implemented for `NotZerocopy<AU16>`
+   |
+note: required by a bound in `SRC_NOT_AS_BYTES::transmute`
+  --> tests/ui-msrv/transmute-src-not-asbytes.rs:14:32
+   |
+14 | const SRC_NOT_AS_BYTES: AU16 = transmute!(NotZerocopy(AU16(0)));
+   |                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `SRC_NOT_AS_BYTES::transmute`
+   = note: this error originates in the macro `transmute` (in Nightly builds, run with -Z macro-backtrace for more info)

tests/ui-nightly/transmute-dst-not-frombytes.rs

@@ -0,0 +1,14 @@
+// Copyright 2022 The Fuchsia Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+include!("../../zerocopy-derive/tests/util.rs");
+
+extern crate zerocopy;
+
+use zerocopy::transmute;
+
+fn main() {}
+
+// `transmute` requires that the destination type implements `FromBytes`
+const DST_NOT_FROM_BYTES: NotZerocopy = transmute!(AU16(0));

tests/ui-nightly/transmute-dst-not-frombytes.stderr

@@ -0,0 +1,22 @@
+error[E0277]: the trait bound `NotZerocopy: FromBytes` is not satisfied
+  --> tests/ui-nightly/transmute-dst-not-frombytes.rs:14:41
+   |
+14 | const DST_NOT_FROM_BYTES: NotZerocopy = transmute!(AU16(0));
+   |                                         ^^^^^^^^^^^^^^^^^^^ the trait `FromBytes` is not implemented for `NotZerocopy`
+   |
+   = help: the following other types implement trait `FromBytes`:
+             ()
+             AU16
+             F32<O>
+             F64<O>
+             I128<O>
+             I16<O>
+             I32<O>
+             I64<O>
+           and $N others
+note: required by a bound in `DST_NOT_FROM_BYTES::transmute`
+  --> tests/ui-nightly/transmute-dst-not-frombytes.rs:14:41
+   |
+14 | const DST_NOT_FROM_BYTES: NotZerocopy = transmute!(AU16(0));
+   |                                         ^^^^^^^^^^^^^^^^^^^ required by this bound in `transmute`
+   = note: this error originates in the macro `transmute` (in Nightly builds, run with -Z macro-backtrace for more info)

tests/ui-nightly/transmute-ptr-to-usize.rs

@@ -0,0 +1,16 @@
+// Copyright 2022 The Fuchsia Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+extern crate zerocopy;
+
+use zerocopy::transmute;
+
+fn main() {}
+
+// It is unclear whether we can or should support this transmutation, especially
+// in a const context. This test ensures that even if such a transmutation
+// becomes valid due to the requisite implementations of `FromBytes` being
+// added, that we re-examine whether it should specifically be valid in a const
+// context.
+const POINTER_VALUE: usize = transmute!(&0usize as *const usize);

tests/ui-stable/transmute-illegal.stderr → tests/ui-nightly/transmute-ptr-to-usize.stderr

@@ -1,16 +1,16 @@
 error[E0277]: the trait bound `*const usize: AsBytes` is not satisfied
-  --> tests/ui-stable/transmute-illegal.rs:10:30
+  --> tests/ui-nightly/transmute-ptr-to-usize.rs:16:30
    |
-10 | const POINTER_VALUE: usize = zerocopy::transmute!(&0usize as *const usize);
-   |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+16 | const POINTER_VALUE: usize = transmute!(&0usize as *const usize);
+   |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |                              |
    |                              the trait `AsBytes` is not implemented for `*const usize`
    |                              required by a bound introduced by this call
    |
    = help: the trait `AsBytes` is implemented for `usize`
 note: required by a bound in `POINTER_VALUE::transmute`
-  --> tests/ui-stable/transmute-illegal.rs:10:30
+  --> tests/ui-nightly/transmute-ptr-to-usize.rs:16:30
    |
-10 | const POINTER_VALUE: usize = zerocopy::transmute!(&0usize as *const usize);
-   |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `transmute`
-   = note: this error originates in the macro `zerocopy::transmute` (in Nightly builds, run with -Z macro-backtrace for more info)
+16 | const POINTER_VALUE: usize = transmute!(&0usize as *const usize);
+   |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `transmute`
+   = note: this error originates in the macro `transmute` (in Nightly builds, run with -Z macro-backtrace for more info)

tests/ui-nightly/transmute-size-decrease.rs

@@ -0,0 +1,15 @@
+// Copyright 2022 The Fuchsia Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+include!("../../zerocopy-derive/tests/util.rs");
+
+extern crate zerocopy;
+
+use zerocopy::transmute;
+
+fn main() {}
+
+// Although this is not a soundness requirement, we currently require that the
+// size of the destination type is not smaller than the size of the source type.
+const DECREASE_SIZE: u8 = transmute!(AU16(0));

tests/ui-nightly/transmute-size-decrease.stderr

@@ -0,0 +1,9 @@
+error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
+  --> tests/ui-nightly/transmute-size-decrease.rs:15:27
+   |
+15 | const DECREASE_SIZE: u8 = transmute!(AU16(0));
+   |                           ^^^^^^^^^^^^^^^^^^^
+   |
+   = note: source type: `AU16` (16 bits)
+   = note: target type: `u8` (8 bits)
+   = note: this error originates in the macro `transmute` (in Nightly builds, run with -Z macro-backtrace for more info)

tests/ui-nightly/transmute-size-increase.rs

@@ -0,0 +1,15 @@
+// Copyright 2022 The Fuchsia Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+include!("../../zerocopy-derive/tests/util.rs");
+
+extern crate zerocopy;
+
+use zerocopy::transmute;
+
+fn main() {}
+
+// Although this is not a soundness requirement, we currently require that the
+// size of the destination type is not larger than the size of the source type.
+const INCREASE_SIZE: AU16 = transmute!(0u8);

tests/ui-nightly/transmute-size-increase.stderr

@@ -0,0 +1,9 @@
+error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
+  --> tests/ui-nightly/transmute-size-increase.rs:15:29
+   |
+15 | const INCREASE_SIZE: AU16 = transmute!(0u8);
+   |                             ^^^^^^^^^^^^^^^
+   |
+   = note: source type: `u8` (8 bits)
+   = note: target type: `AU16` (16 bits)
+   = note: this error originates in the macro `transmute` (in Nightly builds, run with -Z macro-backtrace for more info)

tests/ui-nightly/transmute-src-not-asbytes.rs

@@ -0,0 +1,14 @@
+// Copyright 2022 The Fuchsia Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+include!("../../zerocopy-derive/tests/util.rs");
+
+extern crate zerocopy;
+
+use zerocopy::transmute;
+
+fn main() {}
+
+// `transmute` requires that the source type implements `AsBytes`
+const SRC_NOT_AS_BYTES: AU16 = transmute!(NotZerocopy(AU16(0)));

tests/ui-nightly/transmute-src-not-asbytes.stderr

@@ -0,0 +1,25 @@
+error[E0277]: the trait bound `NotZerocopy<AU16>: AsBytes` is not satisfied
+  --> tests/ui-nightly/transmute-src-not-asbytes.rs:14:32
+   |
+14 | const SRC_NOT_AS_BYTES: AU16 = transmute!(NotZerocopy(AU16(0)));
+   |                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |                                |
+   |                                the trait `AsBytes` is not implemented for `NotZerocopy<AU16>`
+   |                                required by a bound introduced by this call
+   |
+   = help: the following other types implement trait `AsBytes`:
+             ()
+             AU16
+             F32<O>
+             F64<O>
+             I128<O>
+             I16<O>
+             I32<O>
+             I64<O>
+           and $N others
+note: required by a bound in `SRC_NOT_AS_BYTES::transmute`
+  --> tests/ui-nightly/transmute-src-not-asbytes.rs:14:32
+   |
+14 | const SRC_NOT_AS_BYTES: AU16 = transmute!(NotZerocopy(AU16(0)));
+   |                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `transmute`
+   = note: this error originates in the macro `transmute` (in Nightly builds, run with -Z macro-backtrace for more info)

tests/ui-stable/transmute-dst-not-frombytes.rs

@@ -0,0 +1 @@
+../ui-nightly/transmute-dst-not-frombytes.rs

tests/ui-stable/transmute-dst-not-frombytes.stderr

@@ -0,0 +1,22 @@
+error[E0277]: the trait bound `NotZerocopy: FromBytes` is not satisfied
+  --> tests/ui-stable/transmute-dst-not-frombytes.rs:14:41
+   |
+14 | const DST_NOT_FROM_BYTES: NotZerocopy = transmute!(AU16(0));
+   |                                         ^^^^^^^^^^^^^^^^^^^ the trait `FromBytes` is not implemented for `NotZerocopy`
+   |
+   = help: the following other types implement trait `FromBytes`:
+             ()
+             AU16
+             F32<O>
+             F64<O>
+             I128<O>
+             I16<O>
+             I32<O>
+             I64<O>
+           and $N others
+note: required by a bound in `DST_NOT_FROM_BYTES::transmute`
+  --> tests/ui-stable/transmute-dst-not-frombytes.rs:14:41
+   |
+14 | const DST_NOT_FROM_BYTES: NotZerocopy = transmute!(AU16(0));
+   |                                         ^^^^^^^^^^^^^^^^^^^ required by this bound in `transmute`
+   = note: this error originates in the macro `transmute` (in Nightly builds, run with -Z macro-backtrace for more info)

tests/ui-stable/transmute-ptr-to-usize.rs

@@ -0,0 +1 @@
+../ui-nightly/transmute-ptr-to-usize.rs

tests/ui-nightly/transmute-illegal.stderr → tests/ui-stable/transmute-ptr-to-usize.stderr

@@ -1,16 +1,16 @@
 error[E0277]: the trait bound `*const usize: AsBytes` is not satisfied
-  --> tests/ui-nightly/transmute-illegal.rs:10:30
+  --> tests/ui-stable/transmute-ptr-to-usize.rs:16:30
    |
-10 | const POINTER_VALUE: usize = zerocopy::transmute!(&0usize as *const usize);
-   |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+16 | const POINTER_VALUE: usize = transmute!(&0usize as *const usize);
+   |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |                              |
    |                              the trait `AsBytes` is not implemented for `*const usize`
    |                              required by a bound introduced by this call
    |
    = help: the trait `AsBytes` is implemented for `usize`
 note: required by a bound in `POINTER_VALUE::transmute`
-  --> tests/ui-nightly/transmute-illegal.rs:10:30
+  --> tests/ui-stable/transmute-ptr-to-usize.rs:16:30
    |
-10 | const POINTER_VALUE: usize = zerocopy::transmute!(&0usize as *const usize);
-   |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `transmute`
-   = note: this error originates in the macro `zerocopy::transmute` (in Nightly builds, run with -Z macro-backtrace for more info)
+16 | const POINTER_VALUE: usize = transmute!(&0usize as *const usize);
+   |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `transmute`
+   = note: this error originates in the macro `transmute` (in Nightly builds, run with -Z macro-backtrace for more info)

tests/ui-stable/transmute-size-decrease.rs

@@ -0,0 +1 @@
+../ui-nightly/transmute-size-decrease.rs

tests/ui-stable/transmute-size-decrease.stderr

@@ -0,0 +1,9 @@
+error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
+  --> tests/ui-stable/transmute-size-decrease.rs:15:27
+   |
+15 | const DECREASE_SIZE: u8 = transmute!(AU16(0));
+   |                           ^^^^^^^^^^^^^^^^^^^
+   |
+   = note: source type: `AU16` (16 bits)
+   = note: target type: `u8` (8 bits)
+   = note: this error originates in the macro `transmute` (in Nightly builds, run with -Z macro-backtrace for more info)

tests/ui-stable/transmute-size-increase.rs

@@ -0,0 +1 @@
+../ui-nightly/transmute-size-increase.rs

tests/ui-stable/transmute-size-increase.stderr

@@ -0,0 +1,9 @@
+error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
+  --> tests/ui-stable/transmute-size-increase.rs:15:29
+   |
+15 | const INCREASE_SIZE: AU16 = transmute!(0u8);
+   |                             ^^^^^^^^^^^^^^^
+   |
+   = note: source type: `u8` (8 bits)
+   = note: target type: `AU16` (16 bits)
+   = note: this error originates in the macro `transmute` (in Nightly builds, run with -Z macro-backtrace for more info)

tests/ui-stable/transmute-src-not-asbytes.rs

@@ -0,0 +1 @@
+../ui-nightly/transmute-src-not-asbytes.rs