major test improvements

library/core/tests/mem.rs

@@ -388,6 +388,115 @@ fn offset_of() {
     assert!(offset_of!((u8, u16), 1) <= size_of::<(u8, u16)>() - 2);
 }
 
+#[test]
+#[cfg(not(bootstrap))]
+fn offset_of_union() {
+    #[repr(C)]
+    union Foo {
+        x: u8,
+        y: u16,
+        z: Bar,
+    }
+
+    #[repr(C)]
+    #[derive(Copy, Clone)]
+    struct Bar(u8, u8);
+
+    assert_eq!(offset_of!(Foo, x), 0);
+    assert_eq!(offset_of!(Foo, y), 0);
+    assert_eq!(offset_of!(Foo, z.0), 0);
+    assert_eq!(offset_of!(Foo, z.1), 1);
+}
+
+#[test]
+#[cfg(not(bootstrap))]
+fn offset_of_dst() {
+    #[repr(C)]
+    struct Alpha {
+        x: u8,
+        y: u16,
+        z: [u8],
+    }
+
+    trait Trait {}
+
+    #[repr(C)]
+    struct Beta {
+        x: u8,
+        y: u16,
+        z: dyn Trait,
+    }
+
+    extern "C" {
+        type Extern;
+    }
+
+    #[repr(C)]
+    struct Gamma {
+        x: u8,
+        y: u16,
+        z: Extern,
+    }
+
+    assert_eq!(offset_of!(Alpha, x), 0);
+    assert_eq!(offset_of!(Alpha, y), 2);
+
+    assert_eq!(offset_of!(Beta, x), 0);
+    assert_eq!(offset_of!(Beta, y), 2);
+
+    assert_eq!(offset_of!(Gamma, x), 0);
+    assert_eq!(offset_of!(Gamma, y), 2);
+}
+
+#[test]
+#[cfg(not(bootstrap))]
+fn offset_of_packed() {
+    #[repr(C, packed)]
+    struct Foo {
+        x: u8,
+        y: u16,
+    }
+
+    assert_eq!(offset_of!(Foo, x), 0);
+    assert_eq!(offset_of!(Foo, y), 1);
+}
+
+#[test]
+#[cfg(not(bootstrap))]
+fn offset_of_projection() {
+    #[repr(C)]
+    struct Foo {
+        x: u8,
+        y: u16,
+    }
+
+    trait Projector {
+        type Type;
+    }
+
+    impl Projector for () {
+        type Type = Foo;
+    }
+
+    assert_eq!(offset_of!(<() as Projector>::Type, x), 0);
+    assert_eq!(offset_of!(<() as Projector>::Type, y), 2);
+}
+
+#[test]
+#[cfg(not(bootstrap))]
+fn offset_of_alias() {
+    #[repr(C)]
+    struct Foo {
+        x: u8,
+        y: u16,
+    }
+
+    type Bar = Foo;
+
+    assert_eq!(offset_of!(Bar, x), 0);
+    assert_eq!(offset_of!(Bar, y), 2);
+}
+
 #[test]
 #[cfg(not(bootstrap))]
 fn const_offset_of() {
@@ -425,20 +534,6 @@ fn offset_of_without_const_promotion() {
     inner::<()>();
 }
 
-#[test]
-#[cfg(not(bootstrap))]
-fn offset_of_dst() {
-    #[repr(C)]
-    struct Foo {
-        x: u8,
-        y: u16,
-        slice: [u8],
-    }
-
-    assert_eq!(offset_of!(Foo, x), 0);
-    assert_eq!(offset_of!(Foo, y), 2);
-}
-
 #[test]
 #[cfg(not(bootstrap))]
 fn offset_of_addr() {

tests/ui/lint/dead-code/offset-of-correct-param-env.rs

@@ -33,7 +33,7 @@ where
     // But importantly, the normalization ends up with T, which, as we've declared in our param
     // env is MyFieldDead. When we're in the param env of the `a` field, the where bound above
     // is not in scope, so we don't know what T is - it's generic.
-    // We cannot access a field on T. Boom!
+    // If we use the wrong param env, the lint will ICE.
     std::mem::offset_of!(A<GenericIsEqual<T>>, a.not_dead)
 }
 

tests/ui/offset-of/auxiliary/offset-of-staged-api.rs

@@ -0,0 +1,33 @@
+#![crate_type = "lib"]
+#![feature(staged_api)]
+#![stable(feature = "stable_test_feature", since = "1.0")]
+
+#[unstable(feature = "unstable_test_feature", issue = "none")]
+pub struct Unstable {
+    #[unstable(feature = "unstable_test_feature", issue = "none")]
+    pub unstable: u8,
+}
+
+#[stable(feature = "stable_test_feature", since = "1.0")]
+pub struct Stable {
+    #[stable(feature = "stable_test_feature", since = "1.0")]
+    pub stable: u8,
+}
+
+#[stable(feature = "stable_test_feature", since = "1.0")]
+pub struct StableWithUnstableField {
+    #[unstable(feature = "unstable_test_feature", issue = "none")]
+    pub unstable: u8,
+}
+
+#[stable(feature = "stable_test_feature", since = "1.0")]
+pub struct StableWithUnstableFieldType {
+    #[stable(feature = "stable_test_feature", since = "1.0")]
+    pub stable: Unstable,
+}
+
+#[unstable(feature = "unstable_test_feature", issue = "none")]
+pub struct UnstableWithStableFieldType {
+    #[unstable(feature = "unstable_test_feature", issue = "none")]
+    pub unstable: Stable,
+}

tests/ui/offset-of/offset-of-dst-field.rs

@@ -1,14 +1,33 @@
-#![feature(offset_of)]
+#![feature(offset_of, extern_types)]
 
 use std::mem::offset_of;
 
-#[repr(C)]
-struct Foo {
+struct Alpha {
     x: u8,
     y: u16,
-    slice: [u8],
+    z: [u8],
+}
+
+trait Trait {}
+
+struct Beta {
+    x: u8,
+    y: u16,
+    z: dyn Trait,
+}
+
+extern {
+    type Extern;
+}
+
+struct Gamma {
+    x: u8,
+    y: u16,
+    z: Extern,
 }
 
 fn main() {
-    offset_of!(Foo, slice); //~ ERROR the size for values of type
+    offset_of!(Alpha, z); //~ ERROR the size for values of type
+    offset_of!(Beta, z); //~ ERROR the size for values of type
+    offset_of!(Gamma, z); //~ ERROR the size for values of type
 }

tests/ui/offset-of/offset-of-dst-field.stderr

@@ -1,11 +1,27 @@
 error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
-  --> $DIR/offset-of-dst-field.rs:13:5
+  --> $DIR/offset-of-dst-field.rs:30:5
    |
-LL |     offset_of!(Foo, slice);
-   |     ^^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
+LL |     offset_of!(Alpha, z);
+   |     ^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
    |
    = help: the trait `Sized` is not implemented for `[u8]`
 
-error: aborting due to previous error
+error[E0277]: the size for values of type `(dyn Trait + 'static)` cannot be known at compilation time
+  --> $DIR/offset-of-dst-field.rs:31:5
+   |
+LL |     offset_of!(Beta, z);
+   |     ^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `(dyn Trait + 'static)`
+
+error[E0277]: the size for values of type `Extern` cannot be known at compilation time
+  --> $DIR/offset-of-dst-field.rs:32:5
+   |
+LL |     offset_of!(Gamma, z);
+   |     ^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `Extern`
+
+error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0277`.

tests/ui/offset-of/offset-of-enum.rs

@@ -0,0 +1,13 @@
+#![feature(offset_of)]
+
+use std::mem::offset_of;
+
+enum Alpha {
+    One(u8),
+    Two(u8),
+}
+
+fn main() {
+    offset_of!(Alpha::One, 0); //~ ERROR expected type, found variant `Alpha::One`
+    offset_of!(Alpha, Two.0); //~ ERROR no field `Two` on type `Alpha`
+}

tests/ui/offset-of/offset-of-enum.stderr

@@ -0,0 +1,19 @@
+error[E0573]: expected type, found variant `Alpha::One`
+  --> $DIR/offset-of-enum.rs:11:16
+   |
+LL |     offset_of!(Alpha::One, 0);
+   |                ^^^^^^^^^^
+   |                |
+   |                not a type
+   |                help: try using the variant's enum: `Alpha`
+
+error[E0609]: no field `Two` on type `Alpha`
+  --> $DIR/offset-of-enum.rs:12:23
+   |
+LL |     offset_of!(Alpha, Two.0);
+   |                       ^^^
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0573, E0609.
+For more information about an error, try `rustc --explain E0573`.

tests/ui/offset-of/offset-of-unstable-with-feature.rs

@@ -0,0 +1,20 @@
+// check-pass
+// aux-build:offset-of-staged-api.rs
+
+#![feature(offset_of, unstable_test_feature)]
+
+use std::mem::offset_of;
+
+extern crate offset_of_staged_api;
+
+use offset_of_staged_api::*;
+
+fn main() {
+    offset_of!(Unstable, unstable);
+    offset_of!(Stable, stable);
+    offset_of!(StableWithUnstableField, unstable);
+    offset_of!(StableWithUnstableFieldType, stable);
+    offset_of!(StableWithUnstableFieldType, stable.unstable);
+    offset_of!(UnstableWithStableFieldType, unstable);
+    offset_of!(UnstableWithStableFieldType, unstable.stable);
+}

tests/ui/offset-of/offset-of-unstable.rs

@@ -0,0 +1,31 @@
+// aux-build:offset-of-staged-api.rs
+
+#![feature(offset_of)]
+
+use std::mem::offset_of;
+
+extern crate offset_of_staged_api;
+
+use offset_of_staged_api::*;
+
+fn main() {
+    offset_of!(
+        //~^ ERROR use of unstable library feature
+        Unstable, //~ ERROR use of unstable library feature
+        unstable
+    );
+    offset_of!(Stable, stable);
+    offset_of!(StableWithUnstableField, unstable); //~ ERROR use of unstable library feature
+    offset_of!(StableWithUnstableFieldType, stable);
+    offset_of!(StableWithUnstableFieldType, stable.unstable); //~ ERROR use of unstable library feature
+    offset_of!(
+        //~^ ERROR use of unstable library feature
+        UnstableWithStableFieldType, //~ ERROR use of unstable library feature
+        unstable
+    );
+    offset_of!(
+        //~^ ERROR use of unstable library feature
+        UnstableWithStableFieldType, //~ ERROR use of unstable library feature
+        unstable.stable
+    );
+}