Auto merge of #77467 - jyn514:query-docs, r=oli-obk

Normalize `<X as Y>::T` for rustdoc

- Only run for `QPath::Resolved` with `Some` self parameter (`<X as Y>::T`)
- Fall back to the previous behavior if the path can't be resolved

The first commit is a pure refactor and should probably be reviewed by `@GuillaumeGomez.` I recommend reviewing the second commit on its own.

Fixes https://github.com/rust-lang/rust/issues/77459.

r? `@EddyB`
cc `@danielhenrymantilla` , `@lcnr`

src/librustdoc/core.rs

@@ -15,7 +15,7 @@
 use rustc_middle::hir::map::Map;
 use rustc_middle::middle::cstore::CrateStore;
 use rustc_middle::middle::privacy::AccessLevels;
-use rustc_middle::ty::{Ty, TyCtxt};
+use rustc_middle::ty::{ParamEnv, Ty, TyCtxt};
 use rustc_resolve as resolve;
 use rustc_session::config::{self, CrateType, ErrorOutputType};
 use rustc_session::lint;
@@ -25,7 +25,7 @@
 use rustc_span::symbol::sym;
 use rustc_span::DUMMY_SP;
 
-use std::cell::RefCell;
+use std::cell::{Cell, RefCell};
 use std::mem;
 use std::rc::Rc;
 
@@ -42,6 +42,10 @@
 crate struct DocContext<'tcx> {
     crate tcx: TyCtxt<'tcx>,
     crate resolver: Rc<RefCell<interface::BoxedResolver>>,
+    /// Used for normalization.
+    ///
+    /// Most of this logic is copied from rustc_lint::late.
+    crate param_env: Cell<ParamEnv<'tcx>>,
     /// Later on moved into `CACHE_KEY`
     crate renderinfo: RefCell<RenderInfo>,
     /// Later on moved through `clean::Crate` into `CACHE_KEY`
@@ -79,6 +83,13 @@ impl<'tcx> DocContext<'tcx> {
         &self.tcx.sess
     }
 
+    crate fn with_param_env<T, F: FnOnce() -> T>(&self, def_id: DefId, f: F) -> T {
+        let old_param_env = self.param_env.replace(self.tcx.param_env(def_id));
+        let ret = f();
+        self.param_env.set(old_param_env);
+        ret
+    }
+
     crate fn enter_resolver<F, R>(&self, f: F) -> R
     where
         F: FnOnce(&mut resolve::Resolver<'_>) -> R,
@@ -524,6 +535,7 @@ fn run_global_ctxt(
     let mut ctxt = DocContext {
         tcx,
         resolver,
+        param_env: Cell::new(ParamEnv::empty()),
         external_traits: Default::default(),
         active_extern_traits: Default::default(),
         renderinfo: RefCell::new(renderinfo),

src/test/rustdoc/auxiliary/normalize-assoc-item.rs

+#![crate_name = "inner"]
+pub trait MyTrait {
+    type Y;
+}
+
+impl MyTrait for u32 {
+    type Y = i32;
+}
+
+pub fn foo() -> <u32 as MyTrait>::Y {
+    0
+}

src/test/rustdoc/normalize-assoc-item.rs

+// ignore-tidy-linelength
+// aux-build:normalize-assoc-item.rs
+// build-aux-docs
+
+pub trait Trait {
+    type X;
+}
+
+impl Trait for usize {
+    type X = isize;
+}
+
+// @has 'normalize_assoc_item/fn.f.html' '//pre[@class="rust fn"]' 'pub fn f() -> isize'
+pub fn f() -> <usize as Trait>::X {
+    0
+}
+
+pub struct S {
+    // @has 'normalize_assoc_item/struct.S.html' '//span[@id="structfield.box_me_up"]' 'box_me_up: Box<S, Global>'
+    pub box_me_up: <S as Trait>::X,
+    // @has 'normalize_assoc_item/struct.S.html' '//span[@id="structfield.generic"]' 'generic: (usize, isize)'
+    pub generic: <Generic<usize> as Trait>::X,
+}
+
+impl Trait for S {
+    type X = Box<S>;
+}
+
+pub struct Generic<Inner>(Inner);
+
+impl<Inner: Trait> Trait for Generic<Inner> {
+    type X = (Inner, Inner::X);
+}
+
+// These can't be normalized because they depend on a generic parameter.
+// However the user can choose whether the text should be displayed as `Inner::X` or `<Inner as Trait>::X`.
+
+// @has 'normalize_assoc_item/struct.Unknown.html' '//pre[@class="rust struct"]' 'pub struct Unknown<Inner: Trait>(pub <Inner as Trait>::X);'
+pub struct Unknown<Inner: Trait>(pub <Inner as Trait>::X);
+
+// @has 'normalize_assoc_item/struct.Unknown2.html' '//pre[@class="rust struct"]' 'pub struct Unknown2<Inner: Trait>(pub Inner::X);'
+pub struct Unknown2<Inner: Trait>(pub Inner::X);
+
+trait Lifetimes<'a> {
+    type Y;
+}
+
+impl<'a> Lifetimes<'a> for usize {
+    type Y = &'a isize;
+}
+
+// @has 'normalize_assoc_item/fn.g.html' '//pre[@class="rust fn"]' "pub fn g() -> &isize"
+pub fn g() -> <usize as Lifetimes<'static>>::Y {
+    &0
+}
+
+// @has 'normalize_assoc_item/constant.A.html' '//pre[@class="rust const"]' "pub const A: &isize"
+pub const A: <usize as Lifetimes<'static>>::Y = &0;
+
+// test cross-crate re-exports
+extern crate inner;
+// @has 'normalize_assoc_item/fn.foo.html' '//pre[@class="rust fn"]' "pub fn foo() -> i32"
+pub use inner::foo;
+
+// @has 'normalize_assoc_item/fn.h.html' '//pre[@class="rust fn"]' "pub fn h<T>() -> IntoIter<T, Global>"
+pub fn h<T>() -> <Vec<T> as IntoIterator>::IntoIter {
+    vec![].into_iter()
+}