Auto merge of #116670 - oli-obk:host_docs, r=fmease

Hide host effect params from docs

addresses (only on nightly, needs backport) https://github.com/rust-lang/rust/issues/116629

r? `@compiler-errors`

cc `@GuillaumeGomez` `@fee1-dead`

src/librustdoc/clean/mod.rs

@@ -521,7 +521,7 @@ fn clean_generic_param_def<'tcx>(
                 },
             )
         }
-        ty::GenericParamDefKind::Const { has_default, .. } => (
+        ty::GenericParamDefKind::Const { has_default, is_host_effect } => (
             def.name,
             GenericParamDefKind::Const {
                 ty: Box::new(clean_middle_ty(
@@ -541,6 +541,7 @@ fn clean_generic_param_def<'tcx>(
                     )),
                     false => None,
                 },
+                is_host_effect,
             },
         ),
     };
@@ -597,6 +598,7 @@ fn clean_generic_param<'tcx>(
                 ty: Box::new(clean_ty(ty, cx)),
                 default: default
                     .map(|ct| Box::new(ty::Const::from_anon_const(cx.tcx, ct.def_id).to_string())),
+                is_host_effect: cx.tcx.has_attr(param.def_id, sym::rustc_host),
             },
         ),
     };
@@ -2508,15 +2510,23 @@ fn clean_generic_args<'tcx>(
         let args = generic_args
             .args
             .iter()
-            .map(|arg| match arg {
+            .filter_map(|arg| {
+                Some(match arg {
                     hir::GenericArg::Lifetime(lt) if !lt.is_anonymous() => {
                         GenericArg::Lifetime(clean_lifetime(*lt, cx))
                     }
                     hir::GenericArg::Lifetime(_) => GenericArg::Lifetime(Lifetime::elided()),
                     hir::GenericArg::Type(ty) => GenericArg::Type(clean_ty(ty, cx)),
+                    // FIXME(effects): This will still emit `<true>` for non-const impls of const traits
+                    hir::GenericArg::Const(ct)
+                        if cx.tcx.has_attr(ct.value.def_id, sym::rustc_host) =>
+                    {
+                        return None;
+                    }
                     hir::GenericArg::Const(ct) => GenericArg::Const(Box::new(clean_const(ct, cx))),
                     hir::GenericArg::Infer(_inf) => GenericArg::Infer,
                 })
+            })
             .collect::<Vec<_>>()
             .into();
         let bindings =

src/librustdoc/clean/types.rs

@@ -1306,7 +1306,7 @@ pub(crate) fn get_bounds(&self) -> Option<&[GenericBound]> {
 pub(crate) enum GenericParamDefKind {
     Lifetime { outlives: Vec<Lifetime> },
     Type { did: DefId, bounds: Vec<GenericBound>, default: Option<Box<Type>>, synthetic: bool },
-    Const { ty: Box<Type>, default: Option<Box<String>> },
+    Const { ty: Box<Type>, default: Option<Box<String>>, is_host_effect: bool },
 }
 
 impl GenericParamDefKind {
@@ -1326,9 +1326,10 @@ pub(crate) fn lifetime(name: Symbol) -> Self {
         Self { name, kind: GenericParamDefKind::Lifetime { outlives: Vec::new() } }
     }
 
-    pub(crate) fn is_synthetic_type_param(&self) -> bool {
+    pub(crate) fn is_synthetic_param(&self) -> bool {
         match self.kind {
-            GenericParamDefKind::Lifetime { .. } | GenericParamDefKind::Const { .. } => false,
+            GenericParamDefKind::Lifetime { .. } => false,
+            GenericParamDefKind::Const { is_host_effect, .. } => is_host_effect,
             GenericParamDefKind::Type { synthetic, .. } => synthetic,
         }
     }

src/librustdoc/clean/utils.rs

@@ -104,6 +104,10 @@ pub(crate) fn ty_args_to_args<'tcx>(
                     arg: index,
                 }),
             ))),
+            // FIXME(effects): this relies on the host effect being called `host`, which users could also name
+            // their const generics.
+            // FIXME(effects): this causes `host = true` and `host = false` generics to also be emitted.
+            GenericArgKind::Const(ct) if let ty::ConstKind::Param(p) = ct.kind() && p.name == sym::host => None,
             GenericArgKind::Const(ct) => {
                 Some(GenericArg::Const(Box::new(clean_middle_const(kind.rebind(ct), cx))))
             }

src/librustdoc/html/format.rs

@@ -250,8 +250,7 @@ pub(crate) fn print<'a, 'tcx: 'a>(
         cx: &'a Context<'tcx>,
     ) -> impl fmt::Display + 'a + Captures<'tcx> {
         display_fn(move |f| {
-            let mut real_params =
+            let mut real_params = self.params.iter().filter(|p| !p.is_synthetic_param()).peekable();
-                self.params.iter().filter(|p| !p.is_synthetic_type_param()).peekable();
             if real_params.peek().is_none() {
                 return Ok(());
             }

src/librustdoc/json/conversions.rs

@@ -453,7 +453,7 @@ fn from_tcx(kind: clean::GenericParamDefKind, tcx: TyCtxt<'_>) -> Self {
                 default: default.map(|x| (*x).into_tcx(tcx)),
                 synthetic,
             },
-            Const { ty, default } => GenericParamDefKind::Const {
+            Const { ty, default, is_host_effect: _ } => GenericParamDefKind::Const {
                 type_: (*ty).into_tcx(tcx),
                 default: default.map(|x| *x),
             },
@@ -491,12 +491,14 @@ fn from_tcx(predicate: clean::WherePredicate, tcx: TyCtxt<'_>) -> Self {
                                 default: default.map(|ty| (*ty).into_tcx(tcx)),
                                 synthetic,
                             },
-                            clean::GenericParamDefKind::Const { ty, default } => {
+                            clean::GenericParamDefKind::Const {
-                                GenericParamDefKind::Const {
+                                ty,
+                                default,
+                                is_host_effect: _,
+                            } => GenericParamDefKind::Const {
                                 type_: (*ty).into_tcx(tcx),
                                 default: default.map(|d| *d),
-                                }
+                            },
-                            }
                         };
                         GenericParamDef { name, kind }
                     })

src/librustdoc/lib.rs

@@ -6,6 +6,7 @@
 #![feature(array_methods)]
 #![feature(assert_matches)]
 #![feature(box_patterns)]
+#![feature(if_let_guard)]
 #![feature(impl_trait_in_assoc_type)]
 #![feature(iter_intersperse)]
 #![feature(lazy_cell)]

tests/rustdoc/const-effect-param.rs

@@ -0,0 +1,12 @@
+#![crate_name = "foo"]
+#![feature(effects, const_trait_impl)]
+
+#[const_trait]
+pub trait Tr {
+    fn f();
+}
+
+// @has foo/fn.g.html
+// @has - '//pre[@class="rust item-decl"]' 'pub const fn g<T: Tr>()'
+/// foo
+pub const fn g<T: ~const Tr>() {}

tests/rustdoc/const-fn-effects.rs

@@ -0,0 +1,19 @@
+#![crate_name = "foo"]
+#![feature(effects)]
+
+// @has foo/fn.bar.html
+// @has - '//pre[@class="rust item-decl"]' 'pub const fn bar() -> '
+/// foo
+pub const fn bar() -> usize {
+    2
+}
+
+// @has foo/struct.Foo.html
+// @has - '//*[@class="method"]' 'const fn new()'
+pub struct Foo(usize);
+
+impl Foo {
+    pub const fn new() -> Foo {
+        Foo(0)
+    }
+}

tests/rustdoc/inline_cross/auxiliary/const-fn.rs

@@ -0,0 +1,5 @@
+#![feature(effects)]
+
+pub const fn load() -> i32 {
+    0
+}

tests/rustdoc/inline_cross/const-fn.rs

@@ -0,0 +1,10 @@
+// Regression test for issue #116629.
+// Check that we render the correct generic params of const fn
+
+// aux-crate:const_fn=const-fn.rs
+// edition: 2021
+#![crate_name = "user"]
+
+// @has user/fn.load.html
+// @has - '//pre[@class="rust item-decl"]' "pub const fn load() -> i32"
+pub use const_fn::load;