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Auto merge of rust-lang#116236 - dtolnay:builtinmacrocomment, r=cjgillot
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Modernize rustc_builtin_macros generics helpers

- Rustfmt-compatible formatting for the code snippets in comments
- Eliminate an _"Extra scope required"_ obsoleted by NLL
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@bors
bors committed Oct 23, 2023
2 parents 62fae23 + 45363f1 commit a43b129
Showing 1 changed file with 112 additions and 94 deletions.
206 changes: 112 additions & 94 deletions compiler/rustc_builtin_macros/src/deriving/generic/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -37,8 +37,9 @@
//! following snippet
//!
//! ```rust
//! # #![allow(dead_code)]
//! struct A { x : i32 }
//! struct A {
//! x: i32,
//! }
//!
//! struct B(i32);
//!
Expand Down Expand Up @@ -74,6 +75,7 @@
//! trait PartialEq {
//! fn eq(&self, other: &Self) -> bool;
//! }
//!
//! impl PartialEq for i32 {
//! fn eq(&self, other: &i32) -> bool {
//! *self == *other
Expand All @@ -90,22 +92,22 @@
//!
//! ```text
//! Struct(vec![FieldInfo {
//! span: <span of x>
//! name: Some(<ident of x>),
//! self_: <expr for &self.x>,
//! other: vec![<expr for &other.x]
//! }])
//! span: <span of x>,
//! name: Some(<ident of x>),
//! self_: <expr for &self.x>,
//! other: vec![<expr for &other.x>],
//! }])
//! ```
//!
//! For the `B` impl, called with `B(a)` and `B(b)`,
//!
//! ```text
//! Struct(vec![FieldInfo {
//! span: <span of `i32`>,
//! name: None,
//! self_: <expr for &a>
//! other: vec![<expr for &b>]
//! }])
//! span: <span of i32>,
//! name: None,
//! self_: <expr for &a>,
//! other: vec![<expr for &b>],
//! }])
//! ```
//!
//! ## Enums
Expand All @@ -114,33 +116,42 @@
//! == C0(b)`, the SubstructureFields is
//!
//! ```text
//! EnumMatching(0, <ast::Variant for C0>,
//! vec![FieldInfo {
//! span: <span of i32>
//! name: None,
//! self_: <expr for &a>,
//! other: vec![<expr for &b>]
//! }])
//! EnumMatching(
//! 0,
//! <ast::Variant for C0>,
//! vec![FieldInfo {
//! span: <span of i32>,
//! name: None,
//! self_: <expr for &a>,
//! other: vec![<expr for &b>],
//! }],
//! )
//! ```
//!
//! For `C1 {x}` and `C1 {x}`,
//!
//! ```text
//! EnumMatching(1, <ast::Variant for C1>,
//! vec![FieldInfo {
//! span: <span of x>
//! name: Some(<ident of x>),
//! self_: <expr for &self.x>,
//! other: vec![<expr for &other.x>]
//! }])
//! EnumMatching(
//! 1,
//! <ast::Variant for C1>,
//! vec![FieldInfo {
//! span: <span of x>,
//! name: Some(<ident of x>),
//! self_: <expr for &self.x>,
//! other: vec![<expr for &other.x>],
//! }],
//! )
//! ```
//!
//! For the tags,
//!
//! ```text
//! EnumTag(
//! &[<ident of self tag>, <ident of other tag>], <expr to combine with>)
//! &[<ident of self tag>, <ident of other tag>],
//! <expr to combine with>,
//! )
//! ```
//!
//! Note that this setup doesn't allow for the brute-force "match every variant
//! against every other variant" approach, which is bad because it produces a
//! quadratic amount of code (see #15375).
Expand All @@ -154,9 +165,13 @@
//!
//! StaticStruct(<ast::VariantData of B>, Unnamed(vec![<span of x>]))
//!
//! StaticEnum(<ast::EnumDef of C>,
//! vec![(<ident of C0>, <span of C0>, Unnamed(vec![<span of i32>])),
//! (<ident of C1>, <span of C1>, Named(vec![(<ident of x>, <span of x>)]))])
//! StaticEnum(
//! <ast::EnumDef of C>,
//! vec![
//! (<ident of C0>, <span of C0>, Unnamed(vec![<span of i32>])),
//! (<ident of C1>, <span of C1>, Named(vec![(<ident of x>, <span of x>)])),
//! ],
//! )
//! ```
pub use StaticFields::*;
Expand Down Expand Up @@ -522,7 +537,10 @@ impl<'a> TraitDef<'a> {
/// Given that we are deriving a trait `DerivedTrait` for a type like:
///
/// ```ignore (only-for-syntax-highlight)
/// struct Struct<'a, ..., 'z, A, B: DeclaredTrait, C, ..., Z> where C: WhereTrait {
/// struct Struct<'a, ..., 'z, A, B: DeclaredTrait, C, ..., Z>
/// where
/// C: WhereTrait,
/// {
/// a: A,
/// b: B::Item,
/// b1: <B as DeclaredTrait>::Item,
Expand All @@ -535,12 +553,13 @@ impl<'a> TraitDef<'a> {
/// create an impl like:
///
/// ```ignore (only-for-syntax-highlight)
/// impl<'a, ..., 'z, A, B: DeclaredTrait, C, ... Z> where
/// C: WhereTrait,
/// impl<'a, ..., 'z, A, B: DeclaredTrait, C, ..., Z>
/// where
/// C: WhereTrait,
/// A: DerivedTrait + B1 + ... + BN,
/// B: DerivedTrait + B1 + ... + BN,
/// C: DerivedTrait + B1 + ... + BN,
/// B::Item: DerivedTrait + B1 + ... + BN,
/// B::Item: DerivedTrait + B1 + ... + BN,
/// <C as WhereTrait>::Item: DerivedTrait + B1 + ... + BN,
/// ...
/// {
Expand Down Expand Up @@ -676,65 +695,59 @@ impl<'a> TraitDef<'a> {
}
}));

{
// Extra scope required here so ty_params goes out of scope before params is moved

let mut ty_params = params
.iter()
.filter(|param| matches!(param.kind, ast::GenericParamKind::Type { .. }))
.peekable();

if ty_params.peek().is_some() {
let ty_param_names: Vec<Symbol> =
ty_params.map(|ty_param| ty_param.ident.name).collect();

for field_ty in field_tys {
let field_ty_params = find_type_parameters(&field_ty, &ty_param_names, cx);

for field_ty_param in field_ty_params {
// if we have already handled this type, skip it
if let ast::TyKind::Path(_, p) = &field_ty_param.ty.kind
&& let [sole_segment] = &*p.segments
&& ty_param_names.contains(&sole_segment.ident.name)
{
continue;
}
let mut bounds: Vec<_> = self
.additional_bounds
.iter()
.map(|p| {
cx.trait_bound(
p.to_path(cx, self.span, type_ident, generics),
self.is_const,
)
})
.collect();

// Require the current trait.
if !self.skip_path_as_bound {
bounds.push(cx.trait_bound(trait_path.clone(), self.is_const));
}
let ty_param_names: Vec<Symbol> = params
.iter()
.filter(|param| matches!(param.kind, ast::GenericParamKind::Type { .. }))
.map(|ty_param| ty_param.ident.name)
.collect();

// Add a `Copy` bound if required.
if is_packed && self.needs_copy_as_bound_if_packed {
let p = deriving::path_std!(marker::Copy);
bounds.push(cx.trait_bound(
if !ty_param_names.is_empty() {
for field_ty in field_tys {
let field_ty_params = find_type_parameters(&field_ty, &ty_param_names, cx);

for field_ty_param in field_ty_params {
// if we have already handled this type, skip it
if let ast::TyKind::Path(_, p) = &field_ty_param.ty.kind
&& let [sole_segment] = &*p.segments
&& ty_param_names.contains(&sole_segment.ident.name)
{
continue;
}
let mut bounds: Vec<_> = self
.additional_bounds
.iter()
.map(|p| {
cx.trait_bound(
p.to_path(cx, self.span, type_ident, generics),
self.is_const,
));
}
)
})
.collect();

if !bounds.is_empty() {
let predicate = ast::WhereBoundPredicate {
span: self.span,
bound_generic_params: field_ty_param.bound_generic_params,
bounded_ty: field_ty_param.ty,
bounds,
};
// Require the current trait.
if !self.skip_path_as_bound {
bounds.push(cx.trait_bound(trait_path.clone(), self.is_const));
}

let predicate = ast::WherePredicate::BoundPredicate(predicate);
where_clause.predicates.push(predicate);
}
// Add a `Copy` bound if required.
if is_packed && self.needs_copy_as_bound_if_packed {
let p = deriving::path_std!(marker::Copy);
bounds.push(cx.trait_bound(
p.to_path(cx, self.span, type_ident, generics),
self.is_const,
));
}

if !bounds.is_empty() {
let predicate = ast::WhereBoundPredicate {
span: self.span,
bound_generic_params: field_ty_param.bound_generic_params,
bounded_ty: field_ty_param.ty,
bounds,
};

let predicate = ast::WherePredicate::BoundPredicate(predicate);
where_clause.predicates.push(predicate);
}
}
}
Expand Down Expand Up @@ -1026,6 +1039,7 @@ impl<'a> MethodDef<'a> {
}

/// The normal case uses field access.
///
/// ```
/// #[derive(PartialEq)]
/// # struct Dummy;
Expand All @@ -1038,10 +1052,12 @@ impl<'a> MethodDef<'a> {
/// }
/// }
/// ```
///
/// But if the struct is `repr(packed)`, we can't use something like
/// `&self.x` because that might cause an unaligned ref. So for any trait
/// method that takes a reference, we use a local block to force a copy.
/// This requires that the field impl `Copy`.
///
/// ```rust,ignore (example)
/// # struct A { x: u8, y: u8 }
/// impl PartialEq for A {
Expand All @@ -1053,7 +1069,7 @@ impl<'a> MethodDef<'a> {
/// impl Hash for A {
/// fn hash<__H: ::core::hash::Hasher>(&self, state: &mut __H) -> () {
/// ::core::hash::Hash::hash(&{ self.x }, state);
/// ::core::hash::Hash::hash(&{ self.y }, state)
/// ::core::hash::Hash::hash(&{ self.y }, state);
/// }
/// }
/// ```
Expand Down Expand Up @@ -1107,7 +1123,9 @@ impl<'a> MethodDef<'a> {
/// A2(i32)
/// }
/// ```
///
/// is equivalent to:
///
/// ```
/// #![feature(core_intrinsics)]
/// enum A {
Expand All @@ -1119,15 +1137,15 @@ impl<'a> MethodDef<'a> {
/// fn eq(&self, other: &A) -> bool {
/// let __self_tag = ::core::intrinsics::discriminant_value(self);
/// let __arg1_tag = ::core::intrinsics::discriminant_value(other);
/// __self_tag == __arg1_tag &&
/// match (self, other) {
/// (A::A2(__self_0), A::A2(__arg1_0)) =>
/// *__self_0 == *__arg1_0,
/// __self_tag == __arg1_tag
/// && match (self, other) {
/// (A::A2(__self_0), A::A2(__arg1_0)) => *__self_0 == *__arg1_0,
/// _ => true,
/// }
/// }
/// }
/// ```
///
/// Creates a tag check combined with a match for a tuple of all
/// `selflike_args`, with an arm for each variant with fields, possibly an
/// arm for each fieldless variant (if `unify_fieldless_variants` is not
Expand Down Expand Up @@ -1349,7 +1367,7 @@ impl<'a> MethodDef<'a> {
// (Variant1, Variant1, ...) => Body1
// (Variant2, Variant2, ...) => Body2,
// ...
// _ => ::core::intrinsics::unreachable()
// _ => ::core::intrinsics::unreachable(),
// }
let get_match_expr = |mut selflike_args: ThinVec<P<Expr>>| {
let match_arg = if selflike_args.len() == 1 {
Expand Down

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