improper_ctypes_definitions: allow `Box`

This commit stops linting against `Box` in `extern "C" fn`s for the
`improper_ctypes_definitions` lint - boxes are documented to be
FFI-safe.

Signed-off-by: David Wood <david@davidtw.co>

4 files changed, 46 insertions, 63 deletions

diff --git a/src/test/ui/lint/lint-ctypes-fn.rs b/src/test/ui/lint/lint-ctypes-fn.rs
index 67dd7abcf79..aa02e578663 100644
--- a/src/test/ui/lint/lint-ctypes-fn.rs
+++ b/src/test/ui/lint/lint-ctypes-fn.rs
@@ -71,7 +71,8 @@ pub extern "C" fn str_type(p: &str) { }
 //~^ ERROR: uses type `str`
 
 pub extern "C" fn box_type(p: Box<u32>) { }
-//~^ ERROR uses type `std::boxed::Box<u32>`
+
+pub extern "C" fn opt_box_type(p: Option<Box<u32>>) { }
 
 pub extern "C" fn char_type(p: char) { }
 //~^ ERROR uses type `char`
@@ -106,7 +107,6 @@ pub extern "C" fn fn_type2(p: fn()) { }
 //~^ ERROR uses type `fn()`
 
 pub extern "C" fn fn_contained(p: RustBadRet) { }
-//~^ ERROR: uses type `std::boxed::Box<u32>`
 
 pub extern "C" fn transparent_i128(p: TransparentI128) { }
 //~^ ERROR: uses type `i128`
@@ -115,7 +115,6 @@ pub extern "C" fn transparent_str(p: TransparentStr) { }
 //~^ ERROR: uses type `str`
 
 pub extern "C" fn transparent_fn(p: TransparentBadFn) { }
-//~^ ERROR: uses type `std::boxed::Box<u32>`
 
 pub extern "C" fn good3(fptr: Option<extern fn()>) { }
 
diff --git a/src/test/ui/lint/lint-ctypes-fn.stderr b/src/test/ui/lint/lint-ctypes-fn.stderr
index 66cf1953278..d0a449514e5 100644
--- a/src/test/ui/lint/lint-ctypes-fn.stderr
+++ b/src/test/ui/lint/lint-ctypes-fn.stderr
@@ -21,17 +21,8 @@ LL | pub extern "C" fn str_type(p: &str) { }
    = help: consider using `*const u8` and a length instead
    = note: string slices have no C equivalent
 
-error: `extern` fn uses type `std::boxed::Box<u32>`, which is not FFI-safe
-  --> $DIR/lint-ctypes-fn.rs:73:31
-   |
-LL | pub extern "C" fn box_type(p: Box<u32>) { }
-   |                               ^^^^^^^^ not FFI-safe
-   |
-   = help: consider adding a `#[repr(C)]` or `#[repr(transparent)]` attribute to this struct
-   = note: this struct has unspecified layout
-
 error: `extern` fn uses type `char`, which is not FFI-safe
-  --> $DIR/lint-ctypes-fn.rs:76:32
+  --> $DIR/lint-ctypes-fn.rs:77:32
    |
 LL | pub extern "C" fn char_type(p: char) { }
    |                                ^^^^ not FFI-safe
@@ -40,7 +31,7 @@ LL | pub extern "C" fn char_type(p: char) { }
    = note: the `char` type has no C equivalent
 
 error: `extern` fn uses type `i128`, which is not FFI-safe
-  --> $DIR/lint-ctypes-fn.rs:79:32
+  --> $DIR/lint-ctypes-fn.rs:80:32
    |
 LL | pub extern "C" fn i128_type(p: i128) { }
    |                                ^^^^ not FFI-safe
@@ -48,7 +39,7 @@ LL | pub extern "C" fn i128_type(p: i128) { }
    = note: 128-bit integers don't currently have a known stable ABI
 
 error: `extern` fn uses type `u128`, which is not FFI-safe
-  --> $DIR/lint-ctypes-fn.rs:82:32
+  --> $DIR/lint-ctypes-fn.rs:83:32
    |
 LL | pub extern "C" fn u128_type(p: u128) { }
    |                                ^^^^ not FFI-safe
@@ -56,7 +47,7 @@ LL | pub extern "C" fn u128_type(p: u128) { }
    = note: 128-bit integers don't currently have a known stable ABI
 
 error: `extern` fn uses type `(i32, i32)`, which is not FFI-safe
-  --> $DIR/lint-ctypes-fn.rs:85:33
+  --> $DIR/lint-ctypes-fn.rs:86:33
    |
 LL | pub extern "C" fn tuple_type(p: (i32, i32)) { }
    |                                 ^^^^^^^^^^ not FFI-safe
@@ -65,7 +56,7 @@ LL | pub extern "C" fn tuple_type(p: (i32, i32)) { }
    = note: tuples have unspecified layout
 
 error: `extern` fn uses type `(i32, i32)`, which is not FFI-safe
-  --> $DIR/lint-ctypes-fn.rs:88:34
+  --> $DIR/lint-ctypes-fn.rs:89:34
    |
 LL | pub extern "C" fn tuple_type2(p: I32Pair) { }
    |                                  ^^^^^^^ not FFI-safe
@@ -74,7 +65,7 @@ LL | pub extern "C" fn tuple_type2(p: I32Pair) { }
    = note: tuples have unspecified layout
 
 error: `extern` fn uses type `ZeroSize`, which is not FFI-safe
-  --> $DIR/lint-ctypes-fn.rs:91:32
+  --> $DIR/lint-ctypes-fn.rs:92:32
    |
 LL | pub extern "C" fn zero_size(p: ZeroSize) { }
    |                                ^^^^^^^^ not FFI-safe
@@ -88,7 +79,7 @@ LL | pub struct ZeroSize;
    | ^^^^^^^^^^^^^^^^^^^^
 
 error: `extern` fn uses type `ZeroSizeWithPhantomData`, which is not FFI-safe
-  --> $DIR/lint-ctypes-fn.rs:94:40
+  --> $DIR/lint-ctypes-fn.rs:95:40
    |
 LL | pub extern "C" fn zero_size_phantom(p: ZeroSizeWithPhantomData) { }
    |                                        ^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
@@ -101,7 +92,7 @@ LL | pub struct ZeroSizeWithPhantomData(PhantomData<i32>);
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: `extern` fn uses type `std::marker::PhantomData<bool>`, which is not FFI-safe
-  --> $DIR/lint-ctypes-fn.rs:97:51
+  --> $DIR/lint-ctypes-fn.rs:98:51
    |
 LL | pub extern "C" fn zero_size_phantom_toplevel() -> PhantomData<bool> {
    |                                                   ^^^^^^^^^^^^^^^^^ not FFI-safe
@@ -109,7 +100,7 @@ LL | pub extern "C" fn zero_size_phantom_toplevel() -> PhantomData<bool> {
    = note: composed only of `PhantomData`
 
 error: `extern` fn uses type `fn()`, which is not FFI-safe
-  --> $DIR/lint-ctypes-fn.rs:102:30
+  --> $DIR/lint-ctypes-fn.rs:103:30
    |
 LL | pub extern "C" fn fn_type(p: RustFn) { }
    |                              ^^^^^^ not FFI-safe
@@ -118,7 +109,7 @@ LL | pub extern "C" fn fn_type(p: RustFn) { }
    = note: this function pointer has Rust-specific calling convention
 
 error: `extern` fn uses type `fn()`, which is not FFI-safe
-  --> $DIR/lint-ctypes-fn.rs:105:31
+  --> $DIR/lint-ctypes-fn.rs:106:31
    |
 LL | pub extern "C" fn fn_type2(p: fn()) { }
    |                               ^^^^ not FFI-safe
@@ -126,15 +117,6 @@ LL | pub extern "C" fn fn_type2(p: fn()) { }
    = help: consider using an `extern fn(...) -> ...` function pointer instead
    = note: this function pointer has Rust-specific calling convention
 
-error: `extern` fn uses type `std::boxed::Box<u32>`, which is not FFI-safe
-  --> $DIR/lint-ctypes-fn.rs:108:35
-   |
-LL | pub extern "C" fn fn_contained(p: RustBadRet) { }
-   |                                   ^^^^^^^^^^ not FFI-safe
-   |
-   = help: consider adding a `#[repr(C)]` or `#[repr(transparent)]` attribute to this struct
-   = note: this struct has unspecified layout
-
 error: `extern` fn uses type `i128`, which is not FFI-safe
   --> $DIR/lint-ctypes-fn.rs:111:39
    |
@@ -152,17 +134,8 @@ LL | pub extern "C" fn transparent_str(p: TransparentStr) { }
    = help: consider using `*const u8` and a length instead
    = note: string slices have no C equivalent
 
-error: `extern` fn uses type `std::boxed::Box<u32>`, which is not FFI-safe
-  --> $DIR/lint-ctypes-fn.rs:117:37
-   |
-LL | pub extern "C" fn transparent_fn(p: TransparentBadFn) { }
-   |                                     ^^^^^^^^^^^^^^^^ not FFI-safe
-   |
-   = help: consider adding a `#[repr(C)]` or `#[repr(transparent)]` attribute to this struct
-   = note: this struct has unspecified layout
-
 error: `extern` fn uses type `std::marker::PhantomData<bool>`, which is not FFI-safe
-  --> $DIR/lint-ctypes-fn.rs:161:43
+  --> $DIR/lint-ctypes-fn.rs:160:43
    |
 LL | pub extern "C" fn unused_generic2<T>() -> PhantomData<bool> {
    |                                           ^^^^^^^^^^^^^^^^^ not FFI-safe
@@ -170,7 +143,7 @@ LL | pub extern "C" fn unused_generic2<T>() -> PhantomData<bool> {
    = note: composed only of `PhantomData`
 
 error: `extern` fn uses type `std::vec::Vec<T>`, which is not FFI-safe
-  --> $DIR/lint-ctypes-fn.rs:174:39
+  --> $DIR/lint-ctypes-fn.rs:173:39
    |
 LL | pub extern "C" fn used_generic4<T>(x: Vec<T>) { }
    |                                       ^^^^^^ not FFI-safe
@@ -179,7 +152,7 @@ LL | pub extern "C" fn used_generic4<T>(x: Vec<T>) { }
    = note: this struct has unspecified layout
 
 error: `extern` fn uses type `std::vec::Vec<T>`, which is not FFI-safe
-  --> $DIR/lint-ctypes-fn.rs:177:41
+  --> $DIR/lint-ctypes-fn.rs:176:41
    |
 LL | pub extern "C" fn used_generic5<T>() -> Vec<T> {
    |                                         ^^^^^^ not FFI-safe
@@ -187,5 +160,5 @@ LL | pub extern "C" fn used_generic5<T>() -> Vec<T> {
    = help: consider adding a `#[repr(C)]` or `#[repr(transparent)]` attribute to this struct
    = note: this struct has unspecified layout
 
-error: aborting due to 20 previous errors
+error: aborting due to 17 previous errors
 
diff --git a/src/test/ui/lint/lint-ctypes.rs b/src/test/ui/lint/lint-ctypes.rs
index a439a1f339a..bdf95350c70 100644
--- a/src/test/ui/lint/lint-ctypes.rs
+++ b/src/test/ui/lint/lint-ctypes.rs
@@ -48,6 +48,8 @@ extern {
     pub fn slice_type(p: &[u32]); //~ ERROR: uses type `[u32]`
     pub fn str_type(p: &str); //~ ERROR: uses type `str`
     pub fn box_type(p: Box<u32>); //~ ERROR uses type `std::boxed::Box<u32>`
+    pub fn opt_box_type(p: Option<Box<u32>>);
+    //~^ ERROR uses type `std::option::Option<std::boxed::Box<u32>>`
     pub fn char_type(p: char); //~ ERROR uses type `char`
     pub fn i128_type(p: i128); //~ ERROR uses type `i128`
     pub fn u128_type(p: u128); //~ ERROR uses type `u128`
diff --git a/src/test/ui/lint/lint-ctypes.stderr b/src/test/ui/lint/lint-ctypes.stderr
index 9821f858d9c..13b9adca3f9 100644
--- a/src/test/ui/lint/lint-ctypes.stderr
+++ b/src/test/ui/lint/lint-ctypes.stderr
@@ -58,8 +58,17 @@ LL |     pub fn box_type(p: Box<u32>);
    = help: consider adding a `#[repr(C)]` or `#[repr(transparent)]` attribute to this struct
    = note: this struct has unspecified layout
 
+error: `extern` block uses type `std::option::Option<std::boxed::Box<u32>>`, which is not FFI-safe
+  --> $DIR/lint-ctypes.rs:51:28
+   |
+LL |     pub fn opt_box_type(p: Option<Box<u32>>);
+   |                            ^^^^^^^^^^^^^^^^ not FFI-safe
+   |
+   = help: consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum
+   = note: enum has no representation hint
+
 error: `extern` block uses type `char`, which is not FFI-safe
-  --> $DIR/lint-ctypes.rs:51:25
+  --> $DIR/lint-ctypes.rs:53:25
    |
 LL |     pub fn char_type(p: char);
    |                         ^^^^ not FFI-safe
@@ -68,7 +77,7 @@ LL |     pub fn char_type(p: char);
    = note: the `char` type has no C equivalent
 
 error: `extern` block uses type `i128`, which is not FFI-safe
-  --> $DIR/lint-ctypes.rs:52:25
+  --> $DIR/lint-ctypes.rs:54:25
    |
 LL |     pub fn i128_type(p: i128);
    |                         ^^^^ not FFI-safe
@@ -76,7 +85,7 @@ LL |     pub fn i128_type(p: i128);
    = note: 128-bit integers don't currently have a known stable ABI
 
 error: `extern` block uses type `u128`, which is not FFI-safe
-  --> $DIR/lint-ctypes.rs:53:25
+  --> $DIR/lint-ctypes.rs:55:25
    |
 LL |     pub fn u128_type(p: u128);
    |                         ^^^^ not FFI-safe
@@ -84,7 +93,7 @@ LL |     pub fn u128_type(p: u128);
    = note: 128-bit integers don't currently have a known stable ABI
 
 error: `extern` block uses type `dyn std::clone::Clone`, which is not FFI-safe
-  --> $DIR/lint-ctypes.rs:54:26
+  --> $DIR/lint-ctypes.rs:56:26
    |
 LL |     pub fn trait_type(p: &dyn Clone);
    |                          ^^^^^^^^^^ not FFI-safe
@@ -92,7 +101,7 @@ LL |     pub fn trait_type(p: &dyn Clone);
    = note: trait objects have no C equivalent
 
 error: `extern` block uses type `(i32, i32)`, which is not FFI-safe
-  --> $DIR/lint-ctypes.rs:55:26
+  --> $DIR/lint-ctypes.rs:57:26
    |
 LL |     pub fn tuple_type(p: (i32, i32));
    |                          ^^^^^^^^^^ not FFI-safe
@@ -101,7 +110,7 @@ LL |     pub fn tuple_type(p: (i32, i32));
    = note: tuples have unspecified layout
 
 error: `extern` block uses type `(i32, i32)`, which is not FFI-safe
-  --> $DIR/lint-ctypes.rs:56:27
+  --> $DIR/lint-ctypes.rs:58:27
    |
 LL |     pub fn tuple_type2(p: I32Pair);
    |                           ^^^^^^^ not FFI-safe
@@ -110,7 +119,7 @@ LL |     pub fn tuple_type2(p: I32Pair);
    = note: tuples have unspecified layout
 
 error: `extern` block uses type `ZeroSize`, which is not FFI-safe
-  --> $DIR/lint-ctypes.rs:57:25
+  --> $DIR/lint-ctypes.rs:59:25
    |
 LL |     pub fn zero_size(p: ZeroSize);
    |                         ^^^^^^^^ not FFI-safe
@@ -124,7 +133,7 @@ LL | pub struct ZeroSize;
    | ^^^^^^^^^^^^^^^^^^^^
 
 error: `extern` block uses type `ZeroSizeWithPhantomData`, which is not FFI-safe
-  --> $DIR/lint-ctypes.rs:58:33
+  --> $DIR/lint-ctypes.rs:60:33
    |
 LL |     pub fn zero_size_phantom(p: ZeroSizeWithPhantomData);
    |                                 ^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
@@ -137,7 +146,7 @@ LL | pub struct ZeroSizeWithPhantomData(::std::marker::PhantomData<i32>);
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: `extern` block uses type `std::marker::PhantomData<bool>`, which is not FFI-safe
-  --> $DIR/lint-ctypes.rs:61:12
+  --> $DIR/lint-ctypes.rs:63:12
    |
 LL |         -> ::std::marker::PhantomData<bool>;
    |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
@@ -145,7 +154,7 @@ LL |         -> ::std::marker::PhantomData<bool>;
    = note: composed only of `PhantomData`
 
 error: `extern` block uses type `fn()`, which is not FFI-safe
-  --> $DIR/lint-ctypes.rs:62:23
+  --> $DIR/lint-ctypes.rs:64:23
    |
 LL |     pub fn fn_type(p: RustFn);
    |                       ^^^^^^ not FFI-safe
@@ -154,7 +163,7 @@ LL |     pub fn fn_type(p: RustFn);
    = note: this function pointer has Rust-specific calling convention
 
 error: `extern` block uses type `fn()`, which is not FFI-safe
-  --> $DIR/lint-ctypes.rs:63:24
+  --> $DIR/lint-ctypes.rs:65:24
    |
 LL |     pub fn fn_type2(p: fn());
    |                        ^^^^ not FFI-safe
@@ -163,7 +172,7 @@ LL |     pub fn fn_type2(p: fn());
    = note: this function pointer has Rust-specific calling convention
 
 error: `extern` block uses type `std::boxed::Box<u32>`, which is not FFI-safe
-  --> $DIR/lint-ctypes.rs:64:28
+  --> $DIR/lint-ctypes.rs:66:28
    |
 LL |     pub fn fn_contained(p: RustBadRet);
    |                            ^^^^^^^^^^ not FFI-safe
@@ -172,7 +181,7 @@ LL |     pub fn fn_contained(p: RustBadRet);
    = note: this struct has unspecified layout
 
 error: `extern` block uses type `i128`, which is not FFI-safe
-  --> $DIR/lint-ctypes.rs:65:32
+  --> $DIR/lint-ctypes.rs:67:32
    |
 LL |     pub fn transparent_i128(p: TransparentI128);
    |                                ^^^^^^^^^^^^^^^ not FFI-safe
@@ -180,7 +189,7 @@ LL |     pub fn transparent_i128(p: TransparentI128);
    = note: 128-bit integers don't currently have a known stable ABI
 
 error: `extern` block uses type `str`, which is not FFI-safe
-  --> $DIR/lint-ctypes.rs:66:31
+  --> $DIR/lint-ctypes.rs:68:31
    |
 LL |     pub fn transparent_str(p: TransparentStr);
    |                               ^^^^^^^^^^^^^^ not FFI-safe
@@ -189,7 +198,7 @@ LL |     pub fn transparent_str(p: TransparentStr);
    = note: string slices have no C equivalent
 
 error: `extern` block uses type `std::boxed::Box<u32>`, which is not FFI-safe
-  --> $DIR/lint-ctypes.rs:67:30
+  --> $DIR/lint-ctypes.rs:69:30
    |
 LL |     pub fn transparent_fn(p: TransparentBadFn);
    |                              ^^^^^^^^^^^^^^^^ not FFI-safe
@@ -198,7 +207,7 @@ LL |     pub fn transparent_fn(p: TransparentBadFn);
    = note: this struct has unspecified layout
 
 error: `extern` block uses type `[u8; 8]`, which is not FFI-safe
-  --> $DIR/lint-ctypes.rs:68:27
+  --> $DIR/lint-ctypes.rs:70:27
    |
 LL |     pub fn raw_array(arr: [u8; 8]);
    |                           ^^^^^^^ not FFI-safe
@@ -207,7 +216,7 @@ LL |     pub fn raw_array(arr: [u8; 8]);
    = note: passing raw arrays by value is not FFI-safe
 
 error: `extern` block uses type `u128`, which is not FFI-safe
-  --> $DIR/lint-ctypes.rs:70:34
+  --> $DIR/lint-ctypes.rs:72:34
    |
 LL |     pub static static_u128_type: u128;
    |                                  ^^^^ not FFI-safe
@@ -215,12 +224,12 @@ LL |     pub static static_u128_type: u128;
    = note: 128-bit integers don't currently have a known stable ABI
 
 error: `extern` block uses type `u128`, which is not FFI-safe
-  --> $DIR/lint-ctypes.rs:71:40
+  --> $DIR/lint-ctypes.rs:73:40
    |
 LL |     pub static static_u128_array_type: [u128; 16];
    |                                        ^^^^^^^^^^ not FFI-safe
    |
    = note: 128-bit integers don't currently have a known stable ABI
 
-error: aborting due to 23 previous errors
+error: aborting due to 24 previous errors