rustdoc: use ThinVec and Box<str> to shrink clean::ItemKind

src/librustdoc/clean/inline.rs

@@ -3,7 +3,7 @@
 use std::iter::once;
 use std::sync::Arc;
 
-use thin_vec::ThinVec;
+use thin_vec::{thin_vec, ThinVec};
 
 use rustc_ast as ast;
 use rustc_data_structures::fx::FxHashSet;
@@ -596,7 +596,7 @@ fn build_module_items(
                         clean::ImportSource {
                             path: clean::Path {
                                 res,
-                                segments: vec![clean::PathSegment {
+                                segments: thin_vec![clean::PathSegment {
                                     name: prim_ty.as_sym(),
                                     args: clean::GenericArgs::AngleBracketed {
                                         args: Default::default(),

src/librustdoc/clean/mod.rs

@@ -227,7 +227,7 @@ pub(crate) fn clean_middle_const<'tcx>(
     // FIXME: instead of storing the stringified expression, store `self` directly instead.
     Constant {
         type_: clean_middle_ty(constant.ty(), cx, None),
-        kind: ConstantKind::TyConst { expr: constant.to_string() },
+        kind: ConstantKind::TyConst { expr: constant.to_string().into() },
     }
 }
 
@@ -1200,7 +1200,7 @@ pub(crate) fn clean_middle_assoc_item<'tcx>(
                         true
                     }
                     (GenericParamDefKind::Const { .. }, GenericArg::Const(c)) => match &c.kind {
-                        ConstantKind::TyConst { expr } => expr == param.name.as_str(),
+                        ConstantKind::TyConst { expr } => **expr == *param.name.as_str(),
                         _ => false,
                     },
                     _ => false,
@@ -1529,7 +1529,7 @@ pub(crate) fn clean_ty<'tcx>(ty: &hir::Ty<'tcx>, cx: &mut DocContext<'tcx>) -> T
                 }
             };
 
-            Array(Box::new(clean_ty(ty, cx)), length)
+            Array(Box::new(clean_ty(ty, cx)), length.into())
         }
         TyKind::Tup(tys) => Tuple(tys.iter().map(|ty| clean_ty(ty, cx)).collect()),
         TyKind::OpaqueDef(item_id, _, _) => {
@@ -1601,7 +1601,7 @@ pub(crate) fn clean_middle_ty<'tcx>(
         ty::Array(ty, mut n) => {
             n = n.eval(cx.tcx, ty::ParamEnv::reveal_all());
             let n = print_const(cx, n);
-            Array(Box::new(clean_middle_ty(ty, cx, None)), n)
+            Array(Box::new(clean_middle_ty(ty, cx, None)), n.into())
         }
         ty::RawPtr(mt) => RawPointer(mt.mutbl, Box::new(clean_middle_ty(mt.ty, cx, None))),
         ty::Ref(r, ty, mutbl) => BorrowedRef {

src/librustdoc/clean/types.rs

@@ -1621,7 +1621,7 @@ pub(crate) enum Type {
     /// An array type.
     ///
     /// The `String` field is a stringified version of the array's length parameter.
-    Array(Box<Type>, String),
+    Array(Box<Type>, Box<str>),
     /// A raw pointer type: `*const i32`, `*mut i32`
     RawPointer(Mutability, Box<Type>),
     /// A reference type: `&i32`, `&'a mut Foo`
@@ -2206,7 +2206,7 @@ impl Span {
 #[derive(Clone, PartialEq, Eq, Debug, Hash)]
 pub(crate) struct Path {
     pub(crate) res: Res,
-    pub(crate) segments: Vec<PathSegment>,
+    pub(crate) segments: ThinVec<PathSegment>,
 }
 
 impl Path {
@@ -2356,7 +2356,7 @@ pub(crate) enum ConstantKind {
     ///
     /// Note that `ty::Const` includes generic parameters, and may not always be uniquely identified
     /// by a DefId. So this field must be different from `Extern`.
-    TyConst { expr: String },
+    TyConst { expr: Box<str> },
     /// A constant (expression) that's not an item or associated item. These are usually found
     /// nested inside types (e.g., array lengths) or expressions (e.g., repeat counts), and also
     /// used to define explicit discriminant values for enum variants.
@@ -2384,7 +2384,7 @@ impl Constant {
 impl ConstantKind {
     pub(crate) fn expr(&self, tcx: TyCtxt<'_>) -> String {
         match *self {
-            ConstantKind::TyConst { ref expr } => expr.clone(),
+            ConstantKind::TyConst { ref expr } => expr.to_string(),
             ConstantKind::Extern { def_id } => print_inlined_const(tcx, def_id),
             ConstantKind::Local { body, .. } | ConstantKind::Anonymous { body } => {
                 print_const_expr(tcx, body)
@@ -2570,13 +2570,13 @@ mod size_asserts {
     // tidy-alphabetical-start
     static_assert_size!(Crate, 72); // frequently moved by-value
     static_assert_size!(DocFragment, 32);
-    static_assert_size!(GenericArg, 48);
+    static_assert_size!(GenericArg, 32);
     static_assert_size!(GenericArgs, 32);
     static_assert_size!(GenericParamDef, 56);
     static_assert_size!(Generics, 16);
     static_assert_size!(Item, 56);
-    static_assert_size!(ItemKind, 88);
+    static_assert_size!(ItemKind, 64);
     static_assert_size!(PathSegment, 40);
-    static_assert_size!(Type, 48);
+    static_assert_size!(Type, 32);
     // tidy-alphabetical-end
 }

src/librustdoc/clean/utils.rs

@@ -21,7 +21,7 @@ use rustc_middle::ty::{self, DefIdTree, TyCtxt};
 use rustc_span::symbol::{kw, sym, Symbol};
 use std::fmt::Write as _;
 use std::mem;
-use thin_vec::ThinVec;
+use thin_vec::{thin_vec, ThinVec};
 
 #[cfg(test)]
 mod tests;
@@ -136,7 +136,7 @@ pub(super) fn external_path<'tcx>(
     let name = cx.tcx.item_name(did);
     Path {
         res: Res::Def(def_kind, did),
-        segments: vec![PathSegment {
+        segments: thin_vec![PathSegment {
             name,
             args: external_generic_args(cx, did, has_self, bindings, substs),
         }],
@@ -242,19 +242,13 @@ pub(crate) fn print_const(cx: &DocContext<'_>, n: ty::Const<'_>) -> String {
 
             s
         }
-        _ => {
-            let mut s = n.to_string();
-            // array lengths are obviously usize
-            if s.ends_with("_usize") {
-                let n = s.len() - "_usize".len();
-                s.truncate(n);
-                if s.ends_with(": ") {
-                    let n = s.len() - ": ".len();
-                    s.truncate(n);
-                }
-            }
-            s
+        // array lengths are obviously usize
+        ty::ConstKind::Value(ty::ValTree::Leaf(scalar))
+            if *n.ty().kind() == ty::Uint(ty::UintTy::Usize) =>
+        {
+            scalar.to_string()
         }
+        _ => n.to_string(),
     }
 }
 

src/librustdoc/json/conversions.rs

@@ -485,7 +485,7 @@ impl FromWithTcx<clean::Type> for Type {
             BareFunction(f) => Type::FunctionPointer(Box::new((*f).into_tcx(tcx))),
             Tuple(t) => Type::Tuple(t.into_tcx(tcx)),
             Slice(t) => Type::Slice(Box::new((*t).into_tcx(tcx))),
-            Array(t, s) => Type::Array { type_: Box::new((*t).into_tcx(tcx)), len: s },
+            Array(t, s) => Type::Array { type_: Box::new((*t).into_tcx(tcx)), len: s.to_string() },
             ImplTrait(g) => Type::ImplTrait(g.into_tcx(tcx)),
             Infer => Type::Infer,
             RawPointer(mutability, type_) => Type::RawPointer {