From c6015851f7e54d1e1e267afb315a2b4b23096d0d Mon Sep 17 00:00:00 2001
From: Michael Howell <michael@notriddle.com>
Date: Thu, 9 Mar 2023 13:18:07 -0700
Subject: [PATCH 1/5] rustdoc: move notable trait tests into their own
 directory

---
 .../doc-notable_trait-mut_t_is_not_an_iterator.rs                 | 0
 .../{ => notable-trait}/doc-notable_trait-mut_t_is_not_ref_t.rs   | 0
 .../doc-notable_trait-slice.bare_fn_matches.html                  | 0
 tests/rustdoc/{ => notable-trait}/doc-notable_trait-slice.rs      | 0
 tests/rustdoc/{ => notable-trait}/doc-notable_trait.bare-fn.html  | 0
 tests/rustdoc/{ => notable-trait}/doc-notable_trait.rs            | 0
 .../{ => notable-trait}/doc-notable_trait.some-struct-new.html    | 0
 tests/rustdoc/{ => notable-trait}/doc-notable_trait.wrap-me.html  | 0
 .../doc-notable_trait_box_is_not_an_iterator.rs                   | 0
 .../{ => notable-trait}/spotlight-from-dependency.odd.html        | 0
 tests/rustdoc/{ => notable-trait}/spotlight-from-dependency.rs    | 0
 11 files changed, 0 insertions(+), 0 deletions(-)
 rename tests/rustdoc/{ => notable-trait}/doc-notable_trait-mut_t_is_not_an_iterator.rs (100%)
 rename tests/rustdoc/{ => notable-trait}/doc-notable_trait-mut_t_is_not_ref_t.rs (100%)
 rename tests/rustdoc/{ => notable-trait}/doc-notable_trait-slice.bare_fn_matches.html (100%)
 rename tests/rustdoc/{ => notable-trait}/doc-notable_trait-slice.rs (100%)
 rename tests/rustdoc/{ => notable-trait}/doc-notable_trait.bare-fn.html (100%)
 rename tests/rustdoc/{ => notable-trait}/doc-notable_trait.rs (100%)
 rename tests/rustdoc/{ => notable-trait}/doc-notable_trait.some-struct-new.html (100%)
 rename tests/rustdoc/{ => notable-trait}/doc-notable_trait.wrap-me.html (100%)
 rename tests/rustdoc/{ => notable-trait}/doc-notable_trait_box_is_not_an_iterator.rs (100%)
 rename tests/rustdoc/{ => notable-trait}/spotlight-from-dependency.odd.html (100%)
 rename tests/rustdoc/{ => notable-trait}/spotlight-from-dependency.rs (100%)

diff --git a/tests/rustdoc/doc-notable_trait-mut_t_is_not_an_iterator.rs b/tests/rustdoc/notable-trait/doc-notable_trait-mut_t_is_not_an_iterator.rs
similarity index 100%
rename from tests/rustdoc/doc-notable_trait-mut_t_is_not_an_iterator.rs
rename to tests/rustdoc/notable-trait/doc-notable_trait-mut_t_is_not_an_iterator.rs
diff --git a/tests/rustdoc/doc-notable_trait-mut_t_is_not_ref_t.rs b/tests/rustdoc/notable-trait/doc-notable_trait-mut_t_is_not_ref_t.rs
similarity index 100%
rename from tests/rustdoc/doc-notable_trait-mut_t_is_not_ref_t.rs
rename to tests/rustdoc/notable-trait/doc-notable_trait-mut_t_is_not_ref_t.rs
diff --git a/tests/rustdoc/doc-notable_trait-slice.bare_fn_matches.html b/tests/rustdoc/notable-trait/doc-notable_trait-slice.bare_fn_matches.html
similarity index 100%
rename from tests/rustdoc/doc-notable_trait-slice.bare_fn_matches.html
rename to tests/rustdoc/notable-trait/doc-notable_trait-slice.bare_fn_matches.html
diff --git a/tests/rustdoc/doc-notable_trait-slice.rs b/tests/rustdoc/notable-trait/doc-notable_trait-slice.rs
similarity index 100%
rename from tests/rustdoc/doc-notable_trait-slice.rs
rename to tests/rustdoc/notable-trait/doc-notable_trait-slice.rs
diff --git a/tests/rustdoc/doc-notable_trait.bare-fn.html b/tests/rustdoc/notable-trait/doc-notable_trait.bare-fn.html
similarity index 100%
rename from tests/rustdoc/doc-notable_trait.bare-fn.html
rename to tests/rustdoc/notable-trait/doc-notable_trait.bare-fn.html
diff --git a/tests/rustdoc/doc-notable_trait.rs b/tests/rustdoc/notable-trait/doc-notable_trait.rs
similarity index 100%
rename from tests/rustdoc/doc-notable_trait.rs
rename to tests/rustdoc/notable-trait/doc-notable_trait.rs
diff --git a/tests/rustdoc/doc-notable_trait.some-struct-new.html b/tests/rustdoc/notable-trait/doc-notable_trait.some-struct-new.html
similarity index 100%
rename from tests/rustdoc/doc-notable_trait.some-struct-new.html
rename to tests/rustdoc/notable-trait/doc-notable_trait.some-struct-new.html
diff --git a/tests/rustdoc/doc-notable_trait.wrap-me.html b/tests/rustdoc/notable-trait/doc-notable_trait.wrap-me.html
similarity index 100%
rename from tests/rustdoc/doc-notable_trait.wrap-me.html
rename to tests/rustdoc/notable-trait/doc-notable_trait.wrap-me.html
diff --git a/tests/rustdoc/doc-notable_trait_box_is_not_an_iterator.rs b/tests/rustdoc/notable-trait/doc-notable_trait_box_is_not_an_iterator.rs
similarity index 100%
rename from tests/rustdoc/doc-notable_trait_box_is_not_an_iterator.rs
rename to tests/rustdoc/notable-trait/doc-notable_trait_box_is_not_an_iterator.rs
diff --git a/tests/rustdoc/spotlight-from-dependency.odd.html b/tests/rustdoc/notable-trait/spotlight-from-dependency.odd.html
similarity index 100%
rename from tests/rustdoc/spotlight-from-dependency.odd.html
rename to tests/rustdoc/notable-trait/spotlight-from-dependency.odd.html
diff --git a/tests/rustdoc/spotlight-from-dependency.rs b/tests/rustdoc/notable-trait/spotlight-from-dependency.rs
similarity index 100%
rename from tests/rustdoc/spotlight-from-dependency.rs
rename to tests/rustdoc/notable-trait/spotlight-from-dependency.rs

From ee6b228b6a8b874ca8b6e88cd58d4618cf20fb20 Mon Sep 17 00:00:00 2001
From: Michael Howell <michael@notriddle.com>
Date: Thu, 9 Mar 2023 13:41:13 -0700
Subject: [PATCH 2/5] rustdoc: handle generics better when matching notable
 traits

This commit makes the `clean::Type::is_same` non-commutative, so
that a generic `impl` matches a concrete return, but a generic return
does not match a concrete `impl`. It makes slice and vector Write
for `u8` not match on every generic return value.
---
 src/librustdoc/clean/types.rs                 | 46 +++++++++++++++++--
 src/librustdoc/clean/types/tests.rs           | 11 +++++
 src/librustdoc/html/render/mod.rs             |  4 +-
 .../notable-trait/doc-notable_trait-slice.rs  |  6 +++
 .../notable-trait/notable-trait-generics.rs   | 35 ++++++++++++++
 5 files changed, 96 insertions(+), 6 deletions(-)
 create mode 100644 tests/rustdoc/notable-trait/notable-trait-generics.rs

diff --git a/src/librustdoc/clean/types.rs b/src/librustdoc/clean/types.rs
index 6d8380c5fcc18..5217de7aa8a4f 100644
--- a/src/librustdoc/clean/types.rs
+++ b/src/librustdoc/clean/types.rs
@@ -1471,11 +1471,37 @@ impl Type {
         result
     }
 
-    /// Check if two types are "potentially the same".
+    pub(crate) fn is_borrowed_ref(&self) -> bool {
+        matches!(self, Type::BorrowedRef { .. })
+    }
+
+    /// Check if two types are "the same" for documentation purposes.
+    ///
     /// This is different from `Eq`, because it knows that things like
     /// `Placeholder` are possible matches for everything.
+    ///
+    /// This relation is not commutative when generics are involved:
+    ///
+    /// ```ignore(private)
+    /// # // see types/tests.rs:is_same_generic for the real test
+    /// use rustdoc::format::cache::Cache;
+    /// use rustdoc::clean::types::{Type, PrimitiveType};
+    /// let cache = Cache::new(false);
+    /// let generic = Type::Generic(rustc_span::symbol::sym::Any);
+    /// let unit = Type::Primitive(PrimitiveType::Unit);
+    /// assert!(!generic.is_same(&unit, &cache));
+    /// assert!(unit.is_same(&generic, &cache));
+    /// ```
+    ///
+    /// An owned type is also the same as its borrowed variants (this is commutative),
+    /// but `&T` is not the same as `&mut T`.
     pub(crate) fn is_same(&self, other: &Self, cache: &Cache) -> bool {
-        match (self, other) {
+        let (self_cleared, other_cleared) = if !self.is_borrowed_ref() || !other.is_borrowed_ref() {
+            (self.without_borrowed_ref(), other.without_borrowed_ref())
+        } else {
+            (self, other)
+        };
+        match (self_cleared, other_cleared) {
             // Recursive cases.
             (Type::Tuple(a), Type::Tuple(b)) => {
                 a.len() == b.len() && a.iter().zip(b).all(|(a, b)| a.is_same(b, cache))
@@ -1489,9 +1515,21 @@ impl Type {
                 Type::BorrowedRef { mutability, type_, .. },
                 Type::BorrowedRef { mutability: b_mutability, type_: b_type_, .. },
             ) => mutability == b_mutability && type_.is_same(b_type_, cache),
-            // Placeholders and generics are equal to all other types.
+            // Placeholders are equal to all other types.
             (Type::Infer, _) | (_, Type::Infer) => true,
-            (Type::Generic(_), _) | (_, Type::Generic(_)) => true,
+            // Generics match everything on the right, but not on the left.
+            (_, Type::Generic(_)) => true,
+            (Type::Generic(_), _) => false,
+            // Paths account for both the path itself and its generics.
+            (Type::Path { path: a }, Type::Path { path: b }) => {
+                a.def_id() == b.def_id()
+                    && a.generics()
+                        .zip(b.generics())
+                        .map(|(ag, bg)| {
+                            ag.iter().zip(bg.iter()).all(|(at, bt)| at.is_same(bt, cache))
+                        })
+                        .unwrap_or(true)
+            }
             // Other cases, such as primitives, just use recursion.
             (a, b) => a
                 .def_id(cache)
diff --git a/src/librustdoc/clean/types/tests.rs b/src/librustdoc/clean/types/tests.rs
index 20627c2cfc164..7df87a9804aa2 100644
--- a/src/librustdoc/clean/types/tests.rs
+++ b/src/librustdoc/clean/types/tests.rs
@@ -69,3 +69,14 @@ fn should_not_trim() {
     run_test("\t    line1  \n\t    line2", "line1  \nline2");
     run_test("    \tline1  \n    \tline2", "line1  \nline2");
 }
+
+#[test]
+fn is_same_generic() {
+    use crate::clean::types::{PrimitiveType, Type};
+    use crate::formats::cache::Cache;
+    let cache = Cache::new(false);
+    let generic = Type::Generic(rustc_span::symbol::sym::Any);
+    let unit = Type::Primitive(PrimitiveType::Unit);
+    assert!(!generic.is_same(&unit, &cache));
+    assert!(unit.is_same(&generic, &cache));
+}
diff --git a/src/librustdoc/html/render/mod.rs b/src/librustdoc/html/render/mod.rs
index e6a040d02e565..f8c26dc4706b1 100644
--- a/src/librustdoc/html/render/mod.rs
+++ b/src/librustdoc/html/render/mod.rs
@@ -1291,7 +1291,7 @@ pub(crate) fn notable_traits_button(ty: &clean::Type, cx: &mut Context<'_>) -> O
     if let Some(impls) = cx.cache().impls.get(&did) {
         for i in impls {
             let impl_ = i.inner_impl();
-            if !impl_.for_.without_borrowed_ref().is_same(ty.without_borrowed_ref(), cx.cache()) {
+            if !ty.is_same(&impl_.for_, cx.cache()) {
                 // Two different types might have the same did,
                 // without actually being the same.
                 continue;
@@ -1327,7 +1327,7 @@ fn notable_traits_decl(ty: &clean::Type, cx: &Context<'_>) -> (String, String) {
 
     for i in impls {
         let impl_ = i.inner_impl();
-        if !impl_.for_.without_borrowed_ref().is_same(ty.without_borrowed_ref(), cx.cache()) {
+        if !ty.is_same(&impl_.for_, cx.cache()) {
             // Two different types might have the same did,
             // without actually being the same.
             continue;
diff --git a/tests/rustdoc/notable-trait/doc-notable_trait-slice.rs b/tests/rustdoc/notable-trait/doc-notable_trait-slice.rs
index 2411da8cd4549..ef206710b4b08 100644
--- a/tests/rustdoc/notable-trait/doc-notable_trait-slice.rs
+++ b/tests/rustdoc/notable-trait/doc-notable_trait-slice.rs
@@ -18,3 +18,9 @@ pub fn bare_fn_matches() -> &'static [SomeStruct] {
 pub fn bare_fn_no_matches() -> &'static [OtherStruct] {
     &[]
 }
+
+// @has doc_notable_trait_slice/fn.bare_fn_mut_no_matches.html
+// @count - '//script[@id="notable-traits-data"]' 0
+pub fn bare_fn_mut_no_matches() -> &'static mut [SomeStruct] {
+    &mut []
+}
diff --git a/tests/rustdoc/notable-trait/notable-trait-generics.rs b/tests/rustdoc/notable-trait/notable-trait-generics.rs
new file mode 100644
index 0000000000000..7bfe9d43ea986
--- /dev/null
+++ b/tests/rustdoc/notable-trait/notable-trait-generics.rs
@@ -0,0 +1,35 @@
+#![feature(doc_notable_trait)]
+
+// Notable traits SHOULD be shown when the `impl` has a generic type and the
+// return type has a concrete type.
+pub mod generic_return {
+    pub struct Wrapper<T>(T);
+
+    #[doc(notable_trait)]
+    pub trait NotableTrait {}
+
+    impl NotableTrait for Wrapper<u8> {}
+
+    // @has notable_trait_generics/generic_return/fn.returning.html
+    // @!has - '//a[@class="tooltip"]/@data-notable-ty' 'Wrapper<T>'
+    pub fn returning<T>() -> Wrapper<T> {
+        loop {}
+    }
+}
+
+// Notable traits SHOULD NOT be shown when the `impl` has a concrete type and
+// the return type has a generic type.
+pub mod generic_impl {
+    pub struct Wrapper<T>(T);
+
+    #[doc(notable_trait)]
+    pub trait NotableTrait {}
+
+    impl<T> NotableTrait for Wrapper<T> {}
+
+    // @has notable_trait_generics/generic_impl/fn.returning.html
+    // @has - '//a[@class="tooltip"]/@data-notable-ty' 'Wrapper<u8>'
+    pub fn returning() -> Wrapper<u8> {
+        loop {}
+    }
+}

From 86179c4549e74acf22fc4da02b64f0bb2ce1f4aa Mon Sep 17 00:00:00 2001
From: Michael Howell <michael@notriddle.com>
Date: Sun, 12 Mar 2023 17:45:15 -0700
Subject: [PATCH 3/5] rustdoc: rename `Type::is_same` to `is_doc_subtype_of`

---
 src/librustdoc/clean/types.rs       | 14 +++++++-------
 src/librustdoc/clean/types/tests.rs |  4 ++--
 src/librustdoc/html/render/mod.rs   |  4 ++--
 3 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/src/librustdoc/clean/types.rs b/src/librustdoc/clean/types.rs
index 5217de7aa8a4f..1b8478ee21c68 100644
--- a/src/librustdoc/clean/types.rs
+++ b/src/librustdoc/clean/types.rs
@@ -1495,7 +1495,7 @@ impl Type {
     ///
     /// An owned type is also the same as its borrowed variants (this is commutative),
     /// but `&T` is not the same as `&mut T`.
-    pub(crate) fn is_same(&self, other: &Self, cache: &Cache) -> bool {
+    pub(crate) fn is_doc_subtype_of(&self, other: &Self, cache: &Cache) -> bool {
         let (self_cleared, other_cleared) = if !self.is_borrowed_ref() || !other.is_borrowed_ref() {
             (self.without_borrowed_ref(), other.without_borrowed_ref())
         } else {
@@ -1504,17 +1504,17 @@ impl Type {
         match (self_cleared, other_cleared) {
             // Recursive cases.
             (Type::Tuple(a), Type::Tuple(b)) => {
-                a.len() == b.len() && a.iter().zip(b).all(|(a, b)| a.is_same(b, cache))
+                a.len() == b.len() && a.iter().zip(b).all(|(a, b)| a.is_doc_subtype_of(b, cache))
             }
-            (Type::Slice(a), Type::Slice(b)) => a.is_same(b, cache),
-            (Type::Array(a, al), Type::Array(b, bl)) => al == bl && a.is_same(b, cache),
+            (Type::Slice(a), Type::Slice(b)) => a.is_doc_subtype_of(b, cache),
+            (Type::Array(a, al), Type::Array(b, bl)) => al == bl && a.is_doc_subtype_of(b, cache),
             (Type::RawPointer(mutability, type_), Type::RawPointer(b_mutability, b_type_)) => {
-                mutability == b_mutability && type_.is_same(b_type_, cache)
+                mutability == b_mutability && type_.is_doc_subtype_of(b_type_, cache)
             }
             (
                 Type::BorrowedRef { mutability, type_, .. },
                 Type::BorrowedRef { mutability: b_mutability, type_: b_type_, .. },
-            ) => mutability == b_mutability && type_.is_same(b_type_, cache),
+            ) => mutability == b_mutability && type_.is_doc_subtype_of(b_type_, cache),
             // Placeholders are equal to all other types.
             (Type::Infer, _) | (_, Type::Infer) => true,
             // Generics match everything on the right, but not on the left.
@@ -1526,7 +1526,7 @@ impl Type {
                     && a.generics()
                         .zip(b.generics())
                         .map(|(ag, bg)| {
-                            ag.iter().zip(bg.iter()).all(|(at, bt)| at.is_same(bt, cache))
+                            ag.iter().zip(bg.iter()).all(|(at, bt)| at.is_doc_subtype_of(bt, cache))
                         })
                         .unwrap_or(true)
             }
diff --git a/src/librustdoc/clean/types/tests.rs b/src/librustdoc/clean/types/tests.rs
index 7df87a9804aa2..afbee3e5f78ca 100644
--- a/src/librustdoc/clean/types/tests.rs
+++ b/src/librustdoc/clean/types/tests.rs
@@ -77,6 +77,6 @@ fn is_same_generic() {
     let cache = Cache::new(false);
     let generic = Type::Generic(rustc_span::symbol::sym::Any);
     let unit = Type::Primitive(PrimitiveType::Unit);
-    assert!(!generic.is_same(&unit, &cache));
-    assert!(unit.is_same(&generic, &cache));
+    assert!(!generic.is_doc_subtype_of(&unit, &cache));
+    assert!(unit.is_doc_subtype_of(&generic, &cache));
 }
diff --git a/src/librustdoc/html/render/mod.rs b/src/librustdoc/html/render/mod.rs
index f8c26dc4706b1..832c4e7cfe77b 100644
--- a/src/librustdoc/html/render/mod.rs
+++ b/src/librustdoc/html/render/mod.rs
@@ -1291,7 +1291,7 @@ pub(crate) fn notable_traits_button(ty: &clean::Type, cx: &mut Context<'_>) -> O
     if let Some(impls) = cx.cache().impls.get(&did) {
         for i in impls {
             let impl_ = i.inner_impl();
-            if !ty.is_same(&impl_.for_, cx.cache()) {
+            if !ty.is_doc_subtype_of(&impl_.for_, cx.cache()) {
                 // Two different types might have the same did,
                 // without actually being the same.
                 continue;
@@ -1327,7 +1327,7 @@ fn notable_traits_decl(ty: &clean::Type, cx: &Context<'_>) -> (String, String) {
 
     for i in impls {
         let impl_ = i.inner_impl();
-        if !ty.is_same(&impl_.for_, cx.cache()) {
+        if !ty.is_doc_subtype_of(&impl_.for_, cx.cache()) {
             // Two different types might have the same did,
             // without actually being the same.
             continue;

From bfb66eb4bb4ada8a0b4d48d73a93e8f5df0e54be Mon Sep 17 00:00:00 2001
From: Michael Howell <michael@notriddle.com>
Date: Mon, 13 Mar 2023 23:03:53 -0700
Subject: [PATCH 4/5] rustdoc: fix comments in test

---
 tests/rustdoc/notable-trait/notable-trait-generics.rs | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/tests/rustdoc/notable-trait/notable-trait-generics.rs b/tests/rustdoc/notable-trait/notable-trait-generics.rs
index 7bfe9d43ea986..611902abad65b 100644
--- a/tests/rustdoc/notable-trait/notable-trait-generics.rs
+++ b/tests/rustdoc/notable-trait/notable-trait-generics.rs
@@ -1,7 +1,7 @@
 #![feature(doc_notable_trait)]
 
-// Notable traits SHOULD be shown when the `impl` has a generic type and the
-// return type has a concrete type.
+// Notable traits SHOULD NOT be shown when the `impl` has a concrete type and
+// the return type has a generic type.
 pub mod generic_return {
     pub struct Wrapper<T>(T);
 
@@ -17,8 +17,8 @@ pub mod generic_return {
     }
 }
 
-// Notable traits SHOULD NOT be shown when the `impl` has a concrete type and
-// the return type has a generic type.
+// Notable traits SHOULD be shown when the `impl` has a generic type and the
+// return type has a concrete type.
 pub mod generic_impl {
     pub struct Wrapper<T>(T);
 

From 7f76084933b69ae856bc872c3eecdc2378a21f4b Mon Sep 17 00:00:00 2001
From: Michael Howell <michael@notriddle.com>
Date: Fri, 17 Mar 2023 10:46:38 -0700
Subject: [PATCH 5/5] Add clarifying comments

---
 src/librustdoc/clean/types.rs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/librustdoc/clean/types.rs b/src/librustdoc/clean/types.rs
index 1b8478ee21c68..7dbb3f76a0a83 100644
--- a/src/librustdoc/clean/types.rs
+++ b/src/librustdoc/clean/types.rs
@@ -1496,6 +1496,8 @@ impl Type {
     /// An owned type is also the same as its borrowed variants (this is commutative),
     /// but `&T` is not the same as `&mut T`.
     pub(crate) fn is_doc_subtype_of(&self, other: &Self, cache: &Cache) -> bool {
+        // Strip the references so that it can compare the actual types, unless both are references.
+        // If both are references, leave them alone and compare the mutabilities later.
         let (self_cleared, other_cleared) = if !self.is_borrowed_ref() || !other.is_borrowed_ref() {
             (self.without_borrowed_ref(), other.without_borrowed_ref())
         } else {
@@ -1518,6 +1520,7 @@ impl Type {
             // Placeholders are equal to all other types.
             (Type::Infer, _) | (_, Type::Infer) => true,
             // Generics match everything on the right, but not on the left.
+            // If both sides are generic, this returns true.
             (_, Type::Generic(_)) => true,
             (Type::Generic(_), _) => false,
             // Paths account for both the path itself and its generics.