Make rustc_abi compile on stable again

Author: Veykril

Diff for: compiler/rustc_abi/src/callconv.rs

@@ -3,18 +3,23 @@ mod abi {
     pub(crate) use crate::Variants;
 }
 
+#[cfg(feature = "nightly")]
 use rustc_macros::HashStable_Generic;
 
-use crate::{Abi, Align, FieldsShape, HasDataLayout, Size, TyAbiInterface, TyAndLayout};
+#[cfg(feature = "nightly")]
+use crate::{Abi, FieldsShape, TyAbiInterface, TyAndLayout};
+use crate::{Align, HasDataLayout, Size};
 
-#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, HashStable_Generic)]
+#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
 pub enum RegKind {
     Integer,
     Float,
     Vector,
 }
 
-#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, HashStable_Generic)]
+#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
 pub struct Reg {
     pub kind: RegKind,
     pub size: Size,
@@ -108,15 +113,8 @@ impl HomogeneousAggregate {
     }
 }
 
+#[cfg(feature = "nightly")]
 impl<'a, Ty> TyAndLayout<'a, Ty> {
-    /// Returns `true` if this is an aggregate type (including a ScalarPair!)
-    pub fn is_aggregate(&self) -> bool {
-        match self.abi {
-            Abi::Uninhabited | Abi::Scalar(_) | Abi::Vector { .. } => false,
-            Abi::ScalarPair(..) | Abi::Aggregate { .. } => true,
-        }
-    }
-
     /// Returns `Homogeneous` if this layout is an aggregate containing fields of
     /// only a single type (e.g., `(u32, u32)`). Such aggregates are often
     /// special-cased in ABIs.

Diff for: compiler/rustc_abi/src/layout.rs

@@ -11,8 +11,10 @@ use crate::{
     Variants, WrappingRange,
 };
 
+#[cfg(feature = "nightly")]
 mod ty;
 
+#[cfg(feature = "nightly")]
 pub use ty::{FIRST_VARIANT, FieldIdx, Layout, TyAbiInterface, TyAndLayout, VariantIdx};
 
 // A variant is absent if it's uninhabited and only has ZST fields.

Diff for: compiler/rustc_abi/src/lib.rs

@@ -29,14 +29,14 @@ mod layout;
 mod tests;
 
 pub use callconv::{Heterogeneous, HomogeneousAggregate, Reg, RegKind};
-pub use layout::{
-    FIRST_VARIANT, FieldIdx, Layout, LayoutCalculator, LayoutCalculatorError, TyAbiInterface,
-    TyAndLayout, VariantIdx,
-};
+#[cfg(feature = "nightly")]
+pub use layout::{FIRST_VARIANT, FieldIdx, Layout, TyAbiInterface, TyAndLayout, VariantIdx};
+pub use layout::{LayoutCalculator, LayoutCalculatorError};
 
 /// Requirements for a `StableHashingContext` to be used in this crate.
 /// This is a hack to allow using the `HashStable_Generic` derive macro
 /// instead of implementing everything in `rustc_middle`.
+#[cfg(feature = "nightly")]
 pub trait HashStableContext {}
 
 #[derive(Clone, Copy, PartialEq, Eq, Default)]
@@ -1644,6 +1644,14 @@ pub struct LayoutS<FieldIdx: Idx, VariantIdx: Idx> {
 }
 
 impl<FieldIdx: Idx, VariantIdx: Idx> LayoutS<FieldIdx, VariantIdx> {
+    /// Returns `true` if this is an aggregate type (including a ScalarPair!)
+    pub fn is_aggregate(&self) -> bool {
+        match self.abi {
+            Abi::Uninhabited | Abi::Scalar(_) | Abi::Vector { .. } => false,
+            Abi::ScalarPair(..) | Abi::Aggregate { .. } => true,
+        }
+    }
+
     pub fn scalar<C: HasDataLayout>(cx: &C, scalar: Scalar) -> Self {
         let largest_niche = Niche::from_scalar(cx, Size::ZERO, scalar);
         let size = scalar.size(cx);