Rollup merge of #60959 - petrochenkov:sassert, r=estebank

rustc: Improve type size assertions

Now they
- Tell what the new size is, when it changes
- Do not require passing an identifier

```
   ::: src\libsyntax\parse\token.rs:223:1
    |
223 |    static_assert_size!(Token, 123);
    |    -------------------------------- in this macro invocation
    |
    = note: expected type `[(); 123]`
               found type `[(); 16]`
```

src/librustc/hir/mod.rs

@@ -1356,7 +1356,7 @@ pub struct Expr {
 
 // `Expr` is used a lot. Make sure it doesn't unintentionally get bigger.
 #[cfg(target_arch = "x86_64")]
-static_assert!(MEM_SIZE_OF_EXPR: std::mem::size_of::<Expr>() == 72);
+static_assert_size!(Expr, 72);
 
 impl Expr {
     pub fn precedence(&self) -> ExprPrecedence {

src/librustc/middle/region.rs

@@ -158,7 +158,7 @@ newtype_index! {
 impl_stable_hash_for!(struct crate::middle::region::FirstStatementIndex { private });
 
 // compilation error if size of `ScopeData` is not the same as a `u32`
-static_assert!(ASSERT_SCOPE_DATA: mem::size_of::<ScopeData>() == 4);
+static_assert_size!(ScopeData, 4);
 
 impl Scope {
     /// Returns a item-local ID associated with this scope.

src/librustc/mir/interpret/pointer.rs

@@ -78,7 +78,7 @@ pub struct Pointer<Tag=(),Id=AllocId> {
     pub tag: Tag,
 }
 
-static_assert!(POINTER_SIZE: ::std::mem::size_of::<Pointer>() == 16);
+static_assert_size!(Pointer, 16);
 
 /// Produces a `Pointer` which points to the beginning of the Allocation
 impl From<AllocId> for Pointer {

src/librustc/mir/interpret/value.rs

@@ -54,7 +54,7 @@ pub enum ConstValue<'tcx> {
 }
 
 #[cfg(target_arch = "x86_64")]
-static_assert!(CONST_SIZE: ::std::mem::size_of::<ConstValue<'static>>() == 40);
+static_assert_size!(ConstValue<'_>, 40);
 
 impl<'tcx> ConstValue<'tcx> {
     #[inline]
@@ -111,7 +111,7 @@ pub enum Scalar<Tag=(), Id=AllocId> {
 }
 
 #[cfg(target_arch = "x86_64")]
-static_assert!(SCALAR_SIZE: ::std::mem::size_of::<Scalar>() == 24);
+static_assert_size!(Scalar, 24);
 
 impl<Tag> fmt::Display for Scalar<Tag> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {

src/librustc/mir/mod.rs

@@ -1738,7 +1738,7 @@ pub struct Statement<'tcx> {
 
 // `Statement` is used a lot. Make sure it doesn't unintentionally get bigger.
 #[cfg(target_arch = "x86_64")]
-static_assert!(MEM_SIZE_OF_STATEMENT: mem::size_of::<Statement<'_>>() == 56);
+static_assert_size!(Statement<'_>, 56);
 
 impl<'tcx> Statement<'tcx> {
     /// Changes a statement to a nop. This is both faster than deleting instructions and avoids
@@ -1997,10 +1997,9 @@ pub type PlaceProjection<'tcx> = Projection<Place<'tcx>, Local, Ty<'tcx>>;
 /// and the index is a local.
 pub type PlaceElem<'tcx> = ProjectionElem<Local, Ty<'tcx>>;
 
-// at least on 64 bit systems, `PlaceElem` should not be larger than two pointers
-static_assert!(PROJECTION_ELEM_IS_2_PTRS_LARGE:
-    mem::size_of::<PlaceElem<'_>>() <= 16
-);
+// At least on 64 bit systems, `PlaceElem` should not be larger than two pointers.
+#[cfg(target_arch = "x86_64")]
+static_assert_size!(PlaceElem<'_>, 16);
 
 /// Alias for projections as they appear in `UserTypeProjection`, where we
 /// need neither the `V` parameter for `Index` nor the `T` for `Field`.

src/librustc/mir/tcx.rs

@@ -17,9 +17,9 @@ pub struct PlaceTy<'tcx> {
     pub variant_index: Option<VariantIdx>,
 }
 
-static_assert!(PLACE_TY_IS_3_PTRS_LARGE:
-    mem::size_of::<PlaceTy<'_>>() <= 24
-);
+// At least on 64 bit systems, `PlaceTy` should not be larger than two or three pointers.
+#[cfg(target_arch = "x86_64")]
+static_assert_size!(PlaceTy<'_>, 16);
 
 impl<'a, 'gcx, 'tcx> PlaceTy<'tcx> {
     pub fn from_ty(ty: Ty<'tcx>) -> PlaceTy<'tcx> {

src/librustc/ty/mod.rs

@@ -510,7 +510,7 @@ pub struct TyS<'tcx> {
 
 // `TyS` is used a lot. Make sure it doesn't unintentionally get bigger.
 #[cfg(target_arch = "x86_64")]
-static_assert!(MEM_SIZE_OF_TY_S: ::std::mem::size_of::<TyS<'_>>() == 32);
+static_assert_size!(TyS<'_>, 32);
 
 impl<'tcx> Ord for TyS<'tcx> {
     fn cmp(&self, other: &TyS<'tcx>) -> Ordering {

src/librustc/ty/sty.rs

@@ -211,7 +211,7 @@ pub enum TyKind<'tcx> {
 
 // `TyKind` is used a lot. Make sure it doesn't unintentionally get bigger.
 #[cfg(target_arch = "x86_64")]
-static_assert!(MEM_SIZE_OF_TY_KIND: ::std::mem::size_of::<TyKind<'_>>() == 24);
+static_assert_size!(TyKind<'_>, 24);
 
 /// A closure can be modeled as a struct that looks like:
 ///
@@ -2207,7 +2207,7 @@ pub struct Const<'tcx> {
 }
 
 #[cfg(target_arch = "x86_64")]
-static_assert!(CONST_SIZE: ::std::mem::size_of::<Const<'static>>() == 48);
+static_assert_size!(Const<'_>, 48);
 
 impl<'tcx> Const<'tcx> {
     #[inline]

src/librustc_data_structures/macros.rs

@@ -10,3 +10,12 @@ macro_rules! static_assert {
         static $name: () = [()][!($test: bool) as usize];
     }
 }
+
+/// Type size assertion. The first argument is a type and the second argument is its expected size.
+#[macro_export]
+#[allow_internal_unstable(underscore_const_names)]
+macro_rules! static_assert_size {
+    ($ty:ty, $size:expr) => {
+        const _: [(); $size] = [(); ::std::mem::size_of::<$ty>()];
+    }
+}

src/libsyntax/ast.rs

@@ -16,7 +16,7 @@ use crate::ThinVec;
 
 use rustc_data_structures::indexed_vec::Idx;
 #[cfg(target_arch = "x86_64")]
-use rustc_data_structures::static_assert;
+use rustc_data_structures::static_assert_size;
 use rustc_target::spec::abi::Abi;
 use syntax_pos::{Span, DUMMY_SP};
 
@@ -964,7 +964,7 @@ pub struct Expr {
 
 // `Expr` is used a lot. Make sure it doesn't unintentionally get bigger.
 #[cfg(target_arch = "x86_64")]
-static_assert!(MEM_SIZE_OF_EXPR: std::mem::size_of::<Expr>() == 96);
+static_assert_size!(Expr, 96);
 
 impl Expr {
     /// Whether this expression would be valid somewhere that expects a value; for example, an `if`

src/libsyntax/parse/token.rs

@@ -19,7 +19,7 @@ use log::info;
 use std::fmt;
 use std::mem;
 #[cfg(target_arch = "x86_64")]
-use rustc_data_structures::static_assert;
+use rustc_data_structures::static_assert_size;
 use rustc_data_structures::sync::Lrc;
 
 #[derive(Clone, PartialEq, RustcEncodable, RustcDecodable, Hash, Debug, Copy)]
@@ -74,7 +74,7 @@ pub enum Lit {
 }
 
 #[cfg(target_arch = "x86_64")]
-static_assert!(MEM_SIZE_OF_LIT: mem::size_of::<Lit>() == 8);
+static_assert_size!(Lit, 8);
 
 impl Lit {
     crate fn literal_name(&self) -> &'static str {
@@ -220,7 +220,7 @@ pub enum Token {
 
 // `Token` is used a lot. Make sure it doesn't unintentionally get bigger.
 #[cfg(target_arch = "x86_64")]
-static_assert!(MEM_SIZE_OF_STATEMENT: mem::size_of::<Token>() == 16);
+static_assert_size!(Token, 16);
 
 impl Token {
     /// Recovers a `Token` from an `ast::Ident`. This creates a raw identifier if necessary.

src/libsyntax/tokenstream.rs

@@ -21,7 +21,7 @@ use crate::print::pprust;
 
 use syntax_pos::{BytePos, Mark, Span, DUMMY_SP};
 #[cfg(target_arch = "x86_64")]
-use rustc_data_structures::static_assert;
+use rustc_data_structures::static_assert_size;
 use rustc_data_structures::sync::Lrc;
 use serialize::{Decoder, Decodable, Encoder, Encodable};
 use smallvec::{SmallVec, smallvec};
@@ -158,7 +158,7 @@ pub type TreeAndJoint = (TokenTree, IsJoint);
 
 // `TokenStream` is used a lot. Make sure it doesn't unintentionally get bigger.
 #[cfg(target_arch = "x86_64")]
-static_assert!(MEM_SIZE_OF_TOKEN_STREAM: mem::size_of::<TokenStream>() == 8);
+static_assert_size!(TokenStream, 8);
 
 #[derive(Clone, Copy, Debug, PartialEq)]
 pub enum IsJoint {