Auto merge of #82873 - GuillaumeGomez:rustdoc-const-ty, r=jyn514

Rework rustdoc const type

This PR is mostly about two things:
 1. Not storing some information in the `clean::Constant` type
 2. Using `TyCtxt` in the formatting (which we will need in any case as we move forward in any case).

Also: I'm very curious of the perf change in here.

Thanks a lot `@danielhenrymantilla` for your `Captures` idea! It allowed me to solve the lifetime issue completely. :)

r? `@jyn514`

src/librustdoc/clean/inline.rs

@@ -9,7 +9,7 @@ use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::{DefId, CRATE_DEF_INDEX};
 use rustc_hir::Mutability;
 use rustc_metadata::creader::LoadedMacro;
-use rustc_middle::ty;
+use rustc_middle::ty::{self, TyCtxt};
 use rustc_mir::const_eval::is_min_const_fn;
 use rustc_span::hygiene::MacroKind;
 use rustc_span::symbol::{kw, sym, Symbol};
@@ -490,23 +490,19 @@ fn build_module(
     clean::Module { items, is_crate: false }
 }
 
-crate fn print_inlined_const(cx: &DocContext<'_>, did: DefId) -> String {
+crate fn print_inlined_const(tcx: TyCtxt<'_>, did: DefId) -> String {
     if let Some(did) = did.as_local() {
-        let hir_id = cx.tcx.hir().local_def_id_to_hir_id(did);
-        rustc_hir_pretty::id_to_string(&cx.tcx.hir(), hir_id)
+        let hir_id = tcx.hir().local_def_id_to_hir_id(did);
+        rustc_hir_pretty::id_to_string(&tcx.hir(), hir_id)
     } else {
-        cx.tcx.rendered_const(did)
+        tcx.rendered_const(did)
     }
 }
 
-fn build_const(cx: &mut DocContext<'_>, did: DefId) -> clean::Constant {
+fn build_const(cx: &mut DocContext<'_>, def_id: DefId) -> clean::Constant {
     clean::Constant {
-        type_: cx.tcx.type_of(did).clean(cx),
-        expr: print_inlined_const(cx, did),
-        value: clean::utils::print_evaluated_const(cx, did),
-        is_literal: did.as_local().map_or(false, |did| {
-            clean::utils::is_literal_expr(cx, cx.tcx.hir().local_def_id_to_hir_id(did))
-        }),
+        type_: cx.tcx.type_of(def_id).clean(cx),
+        kind: clean::ConstantKind::Extern { def_id },
     }
 }
 

src/librustdoc/clean/mod.rs

@@ -398,9 +398,7 @@ impl Clean<Constant> for hir::ConstArg {
                 .tcx
                 .type_of(cx.tcx.hir().body_owner_def_id(self.value.body).to_def_id())
                 .clean(cx),
-            expr: print_const_expr(cx.tcx, self.value.body),
-            value: None,
-            is_literal: is_literal_expr(cx, self.value.body.hir_id),
+            kind: ConstantKind::Anonymous { body: self.value.body },
         }
     }
 }
@@ -1135,7 +1133,7 @@ impl Clean<Item> for ty::AssocItem {
             ty::AssocKind::Const => {
                 let ty = tcx.type_of(self.def_id);
                 let default = if self.defaultness.has_value() {
-                    Some(inline::print_inlined_const(cx, self.def_id))
+                    Some(inline::print_inlined_const(tcx, self.def_id))
                 } else {
                     None
                 };
@@ -1745,11 +1743,10 @@ impl<'tcx> Clean<Type> for Ty<'tcx> {
 
 impl<'tcx> Clean<Constant> for ty::Const<'tcx> {
     fn clean(&self, cx: &mut DocContext<'_>) -> Constant {
+        // FIXME: instead of storing the stringified expression, store `self` directly instead.
         Constant {
             type_: self.ty.clean(cx),
-            expr: format!("{}", self),
-            value: None,
-            is_literal: false,
+            kind: ConstantKind::TyConst { expr: self.to_string() },
         }
     }
 }
@@ -1953,9 +1950,7 @@ impl Clean<Vec<Item>> for (&hir::Item<'_>, Option<Symbol>) {
                 }
                 ItemKind::Const(ty, body_id) => ConstantItem(Constant {
                     type_: ty.clean(cx),
-                    expr: print_const_expr(cx.tcx, body_id),
-                    value: print_evaluated_const(cx, def_id),
-                    is_literal: is_literal_expr(cx, body_id.hir_id),
+                    kind: ConstantKind::Local { body: body_id, def_id },
                 }),
                 ItemKind::OpaqueTy(ref ty) => OpaqueTyItem(OpaqueTy {
                     bounds: ty.bounds.clean(cx),

src/librustdoc/clean/types.rs

@@ -32,8 +32,9 @@ use rustc_target::spec::abi::Abi;
 
 use crate::clean::cfg::Cfg;
 use crate::clean::external_path;
-use crate::clean::inline;
+use crate::clean::inline::{self, print_inlined_const};
 use crate::clean::types::Type::{QPath, ResolvedPath};
+use crate::clean::utils::{is_literal_expr, print_const_expr, print_evaluated_const};
 use crate::clean::Clean;
 use crate::core::DocContext;
 use crate::formats::cache::Cache;
@@ -1988,9 +1989,58 @@ crate struct Static {
 #[derive(Clone, PartialEq, Eq, Hash, Debug)]
 crate struct Constant {
     crate type_: Type,
-    crate expr: String,
-    crate value: Option<String>,
-    crate is_literal: bool,
+    crate kind: ConstantKind,
+}
+
+#[derive(Clone, PartialEq, Eq, Hash, Debug)]
+crate enum ConstantKind {
+    /// This is the wrapper around `ty::Const` for a non-local constant. Because it doesn't have a
+    /// `BodyId`, we need to handle it on its own.
+    ///
+    /// 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 },
+    /// 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.
+    Anonymous { body: BodyId },
+    /// A constant from a different crate.
+    Extern { def_id: DefId },
+    /// `const FOO: u32 = ...;`
+    Local { def_id: DefId, body: BodyId },
+}
+
+impl Constant {
+    crate fn expr(&self, tcx: TyCtxt<'_>) -> String {
+        match self.kind {
+            ConstantKind::TyConst { ref expr } => expr.clone(),
+            ConstantKind::Extern { def_id } => print_inlined_const(tcx, def_id),
+            ConstantKind::Local { body, .. } | ConstantKind::Anonymous { body } => {
+                print_const_expr(tcx, body)
+            }
+        }
+    }
+
+    crate fn value(&self, tcx: TyCtxt<'_>) -> Option<String> {
+        match self.kind {
+            ConstantKind::TyConst { .. } | ConstantKind::Anonymous { .. } => None,
+            ConstantKind::Extern { def_id } | ConstantKind::Local { def_id, .. } => {
+                print_evaluated_const(tcx, def_id)
+            }
+        }
+    }
+
+    crate fn is_literal(&self, tcx: TyCtxt<'_>) -> bool {
+        match self.kind {
+            ConstantKind::TyConst { .. } => false,
+            ConstantKind::Extern { def_id } => def_id.as_local().map_or(false, |def_id| {
+                is_literal_expr(tcx, tcx.hir().local_def_id_to_hir_id(def_id))
+            }),
+            ConstantKind::Local { body, .. } | ConstantKind::Anonymous { body } => {
+                is_literal_expr(tcx, body.hir_id)
+            }
+        }
+    }
 }
 
 #[derive(Clone, Debug)]

src/librustdoc/clean/utils.rs

@@ -301,7 +301,7 @@ crate fn print_const(cx: &DocContext<'_>, n: &'tcx ty::Const<'_>) -> String {
                 let hir_id = cx.tcx.hir().local_def_id_to_hir_id(def.did);
                 print_const_expr(cx.tcx, cx.tcx.hir().body_owned_by(hir_id))
             } else {
-                inline::print_inlined_const(cx, def.did)
+                inline::print_inlined_const(cx.tcx, def.did)
             };
             if let Some(promoted) = promoted {
                 s.push_str(&format!("::{:?}", promoted))
@@ -324,15 +324,15 @@ crate fn print_const(cx: &DocContext<'_>, n: &'tcx ty::Const<'_>) -> String {
     }
 }
 
-crate fn print_evaluated_const(cx: &DocContext<'_>, def_id: DefId) -> Option<String> {
-    cx.tcx.const_eval_poly(def_id).ok().and_then(|val| {
-        let ty = cx.tcx.type_of(def_id);
+crate fn print_evaluated_const(tcx: TyCtxt<'_>, def_id: DefId) -> Option<String> {
+    tcx.const_eval_poly(def_id).ok().and_then(|val| {
+        let ty = tcx.type_of(def_id);
         match (val, ty.kind()) {
             (_, &ty::Ref(..)) => None,
             (ConstValue::Scalar(_), &ty::Adt(_, _)) => None,
             (ConstValue::Scalar(_), _) => {
-                let const_ = ty::Const::from_value(cx.tcx, val, ty);
-                Some(print_const_with_custom_print_scalar(cx, const_))
+                let const_ = ty::Const::from_value(tcx, val, ty);
+                Some(print_const_with_custom_print_scalar(tcx, const_))
             }
             _ => None,
         }
@@ -349,16 +349,16 @@ fn format_integer_with_underscore_sep(num: &str) -> String {
         .collect()
 }
 
-fn print_const_with_custom_print_scalar(cx: &DocContext<'_>, ct: &'tcx ty::Const<'tcx>) -> String {
+fn print_const_with_custom_print_scalar(tcx: TyCtxt<'_>, ct: &'tcx ty::Const<'tcx>) -> String {
     // Use a slightly different format for integer types which always shows the actual value.
     // For all other types, fallback to the original `pretty_print_const`.
     match (ct.val, ct.ty.kind()) {
         (ty::ConstKind::Value(ConstValue::Scalar(int)), ty::Uint(ui)) => {
             format!("{}{}", format_integer_with_underscore_sep(&int.to_string()), ui.name_str())
         }
         (ty::ConstKind::Value(ConstValue::Scalar(int)), ty::Int(i)) => {
-            let ty = cx.tcx.lift(ct.ty).unwrap();
-            let size = cx.tcx.layout_of(ty::ParamEnv::empty().and(ty)).unwrap().size;
+            let ty = tcx.lift(ct.ty).unwrap();
+            let size = tcx.layout_of(ty::ParamEnv::empty().and(ty)).unwrap().size;
             let data = int.assert_bits(size);
             let sign_extended_data = size.sign_extend(data) as i128;
 
@@ -372,8 +372,8 @@ fn print_const_with_custom_print_scalar(cx: &DocContext<'_>, ct: &'tcx ty::Const
     }
 }
 
-crate fn is_literal_expr(cx: &DocContext<'_>, hir_id: hir::HirId) -> bool {
-    if let hir::Node::Expr(expr) = cx.tcx.hir().get(hir_id) {
+crate fn is_literal_expr(tcx: TyCtxt<'_>, hir_id: hir::HirId) -> bool {
+    if let hir::Node::Expr(expr) = tcx.hir().get(hir_id) {
         if let hir::ExprKind::Lit(_) = &expr.kind {
             return true;
         }
@@ -411,7 +411,7 @@ crate fn resolve_type(cx: &mut DocContext<'_>, path: Path, id: hir::HirId) -> Ty
             return Generic(kw::SelfUpper);
         }
         Res::Def(DefKind::TyParam, _) if path.segments.len() == 1 => {
-            return Generic(Symbol::intern(&format!("{:#}", path.print(&cx.cache))));
+            return Generic(Symbol::intern(&format!("{:#}", path.print(&cx.cache, cx.tcx))));
         }
         Res::SelfTy(..) | Res::Def(DefKind::TyParam | DefKind::AssocTy, _) => true,
         _ => false,