Auto merge of #97224 - matthiaskrgr:rollup-it5nw68, r=matthiaskrgr

Rollup of 7 pull requests

Successful merges:

 - #97109 (Fix misleading `cannot infer type for type parameter` error)
 - #97187 (Reverse condition in Vec::retain_mut doctest)
 - #97201 (Fix typo)
 - #97203 (Minor tweaks to rustc book summary formatting.)
 - #97208 (Do not emit the lint `unused_attributes` for *inherent* `#[doc(hidden)]` associated items)
 - #97215 (Add complexity estimation of iterating over HashSet and HashMap)
 - #97220 (Add regression test for#81827)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs

@@ -866,6 +866,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                 }
             }
 
+            self.report_ambiguous_type_parameter(&mut err, arg);
             err.span_label(
                 span,
                 arg_data.cannot_infer_msg(use_diag.filter(|d| d.applies_to(span))),
@@ -933,6 +934,28 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
         }
     }
 
+    fn report_ambiguous_type_parameter(&self, err: &mut Diagnostic, arg: GenericArg<'tcx>) {
+        if let GenericArgKind::Type(ty) = arg.unpack()
+            && let ty::Infer(ty::TyVar(ty_vid)) = *ty.kind()
+        {
+            let mut inner = self.inner.borrow_mut();
+            let ty_vars = &inner.type_variables();
+            let var_origin = ty_vars.var_origin(ty_vid);
+            if let TypeVariableOriginKind::TypeParameterDefinition(_, Some(def_id)) =
+                var_origin.kind
+                && let Some(parent_def_id) = self.tcx.parent(def_id).as_local()
+                && let Some(node) = self.tcx.hir().find_by_def_id(parent_def_id)
+            {
+                match node {
+                    hir::Node::Item(item) if matches!(item.kind, hir::ItemKind::Impl(_) | hir::ItemKind::Fn(..)) => (),
+                    hir::Node::ImplItem(impl_item) if matches!(impl_item.kind, hir::ImplItemKind::Fn(..)) => (),
+                    _ => return,
+                }
+                err.span_help(self.tcx.def_span(def_id), "type parameter declared here");
+            }
+        }
+    }
+
     pub fn need_type_info_err_in_generator(
         &self,
         kind: hir::GeneratorKind,

compiler/rustc_passes/src/check_attr.rs

@@ -832,7 +832,7 @@ impl CheckAttrVisitor<'_> {
             let parent_hir_id = self.tcx.hir().get_parent_item(hir_id);
             let containing_item = self.tcx.hir().expect_item(parent_hir_id);
 
-            if Target::from_item(containing_item) == Target::Impl {
+            if let hir::ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }) = containing_item.kind {
                 let meta_items = attr.meta_item_list().unwrap();
 
                 let (span, replacement_span) = if meta_items.len() == 1 {

library/alloc/src/vec/mod.rs

@@ -1470,11 +1470,11 @@ impl<T, A: Allocator> Vec<T, A> {
     ///
     /// ```
     /// let mut vec = vec![1, 2, 3, 4];
-    /// vec.retain_mut(|x| if *x > 3 {
-    ///     false
-    /// } else {
+    /// vec.retain_mut(|x| if *x <= 3 {
     ///     *x += 1;
     ///     true
+    /// } else {
+    ///     false
     /// });
     /// assert_eq!(vec, [2, 3, 4]);
     /// ```

library/std/src/collections/hash/map.rs

@@ -344,6 +344,11 @@ impl<K, V, S> HashMap<K, V, S> {
     ///     println!("{key}");
     /// }
     /// ```
+    ///
+    /// # Performance
+    ///
+    /// In the current implementation, iterating over keys takes O(capacity) time
+    /// instead of O(len) because it internally visits empty buckets too.
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn keys(&self) -> Keys<'_, K, V> {
         Keys { inner: self.iter() }
@@ -370,6 +375,11 @@ impl<K, V, S> HashMap<K, V, S> {
     /// vec.sort_unstable();
     /// assert_eq!(vec, ["a", "b", "c"]);
     /// ```
+    ///
+    /// # Performance
+    ///
+    /// In the current implementation, iterating over keys takes O(capacity) time
+    /// instead of O(len) because it internally visits empty buckets too.
     #[inline]
     #[rustc_lint_query_instability]
     #[stable(feature = "map_into_keys_values", since = "1.54.0")]
@@ -395,6 +405,11 @@ impl<K, V, S> HashMap<K, V, S> {
     ///     println!("{val}");
     /// }
     /// ```
+    ///
+    /// # Performance
+    ///
+    /// In the current implementation, iterating over values takes O(capacity) time
+    /// instead of O(len) because it internally visits empty buckets too.
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn values(&self) -> Values<'_, K, V> {
         Values { inner: self.iter() }
@@ -422,6 +437,11 @@ impl<K, V, S> HashMap<K, V, S> {
     ///     println!("{val}");
     /// }
     /// ```
+    ///
+    /// # Performance
+    ///
+    /// In the current implementation, iterating over values takes O(capacity) time
+    /// instead of O(len) because it internally visits empty buckets too.
     #[stable(feature = "map_values_mut", since = "1.10.0")]
     pub fn values_mut(&mut self) -> ValuesMut<'_, K, V> {
         ValuesMut { inner: self.iter_mut() }
@@ -448,6 +468,11 @@ impl<K, V, S> HashMap<K, V, S> {
     /// vec.sort_unstable();
     /// assert_eq!(vec, [1, 2, 3]);
     /// ```
+    ///
+    /// # Performance
+    ///
+    /// In the current implementation, iterating over values takes O(capacity) time
+    /// instead of O(len) because it internally visits empty buckets too.
     #[inline]
     #[rustc_lint_query_instability]
     #[stable(feature = "map_into_keys_values", since = "1.54.0")]
@@ -473,6 +498,11 @@ impl<K, V, S> HashMap<K, V, S> {
     ///     println!("key: {key} val: {val}");
     /// }
     /// ```
+    ///
+    /// # Performance
+    ///
+    /// In the current implementation, iterating over map takes O(capacity) time
+    /// instead of O(len) because it internally visits empty buckets too.
     #[rustc_lint_query_instability]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn iter(&self) -> Iter<'_, K, V> {
@@ -503,6 +533,11 @@ impl<K, V, S> HashMap<K, V, S> {
     ///     println!("key: {key} val: {val}");
     /// }
     /// ```
+    ///
+    /// # Performance
+    ///
+    /// In the current implementation, iterating over map takes O(capacity) time
+    /// instead of O(len) because it internally visits empty buckets too.
     #[rustc_lint_query_instability]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn iter_mut(&mut self) -> IterMut<'_, K, V> {
@@ -633,6 +668,11 @@ impl<K, V, S> HashMap<K, V, S> {
     /// map.retain(|&k, _| k % 2 == 0);
     /// assert_eq!(map.len(), 4);
     /// ```
+    ///
+    /// # Performance
+    ///
+    /// In the current implementation, this operation takes O(capacity) time
+    /// instead of O(len) because it internally visits empty buckets too.
     #[inline]
     #[rustc_lint_query_instability]
     #[stable(feature = "retain_hash_collection", since = "1.18.0")]

library/std/src/collections/hash/set.rs

@@ -184,6 +184,11 @@ impl<T, S> HashSet<T, S> {
     ///     println!("{x}");
     /// }
     /// ```
+    ///
+    /// # Performance
+    ///
+    /// In the current implementation, iterating over set takes O(capacity) time
+    /// instead of O(len) because it internally visits empty buckets too.
     #[inline]
     #[rustc_lint_query_instability]
     #[stable(feature = "rust1", since = "1.0.0")]
@@ -312,6 +317,11 @@ impl<T, S> HashSet<T, S> {
     /// set.retain(|&k| k % 2 == 0);
     /// assert_eq!(set.len(), 3);
     /// ```
+    ///
+    /// # Performance
+    ///
+    /// In the current implementation, this operation takes O(capacity) time
+    /// instead of O(len) because it internally visits empty buckets too.
     #[rustc_lint_query_instability]
     #[stable(feature = "retain_hash_collection", since = "1.18.0")]
     pub fn retain<F>(&mut self, f: F)

src/doc/rustc/src/SUMMARY.md

@@ -1,19 +1,20 @@
 # The Rustc Book
 
 - [What is rustc?](what-is-rustc.md)
-- [Command-line arguments](command-line-arguments.md)
+- [Command-line Arguments](command-line-arguments.md)
+    - [Codegen Options](codegen-options/index.md)
 - [Lints](lints/index.md)
-    - [Lint levels](lints/levels.md)
+    - [Lint Levels](lints/levels.md)
     - [Lint Groups](lints/groups.md)
-    - [Lint listing](lints/listing/index.md)
-        - [Allowed-by-default lints](lints/listing/allowed-by-default.md)
-        - [Warn-by-default lints](lints/listing/warn-by-default.md)
-        - [Deny-by-default lints](lints/listing/deny-by-default.md)
-- [Codegen options](codegen-options/index.md)
+    - [Lint Listing](lints/listing/index.md)
+        - [Allowed-by-default Lints](lints/listing/allowed-by-default.md)
+        - [Warn-by-default Lints](lints/listing/warn-by-default.md)
+        - [Deny-by-default Lints](lints/listing/deny-by-default.md)
 - [JSON Output](json.md)
 - [Tests](tests/index.md)
 - [Platform Support](platform-support.md)
-    - [Template for target-specific documentation](platform-support/TEMPLATE.md)
+    - [Target Tier Policy](target-tier-policy.md)
+    - [Template for Target-specific Documentation](platform-support/TEMPLATE.md)
     - [aarch64-apple-ios-sim](platform-support/aarch64-apple-ios-sim.md)
     - [armv7-unknown-linux-uclibceabi](platform-support/armv7-unknown-linux-uclibceabi.md)
     - [armv7-unknown-linux-uclibceabihf](platform-support/armv7-unknown-linux-uclibceabihf.md)
@@ -25,13 +26,12 @@
     - [*-unknown-openbsd](platform-support/openbsd.md)
     - [wasm64-unknown-unknown](platform-support/wasm64-unknown-unknown.md)
     - [x86_64-unknown-none](platform-support/x86_64-unknown-none.md)
-- [Target Tier Policy](target-tier-policy.md)
 - [Targets](targets/index.md)
     - [Built-in Targets](targets/built-in.md)
     - [Custom Targets](targets/custom.md)
     - [Known Issues](targets/known-issues.md)
 - [Profile-guided Optimization](profile-guided-optimization.md)
 - [Instrumentation-based Code Coverage](instrument-coverage.md)
-- [Linker-plugin based LTO](linker-plugin-lto.md)
+- [Linker-plugin-based LTO](linker-plugin-lto.md)
 - [Exploit Mitigations](exploit-mitigations.md)
 - [Contributing to `rustc`](contributing.md)

src/doc/rustc/src/codegen-options/index.md

@@ -1,4 +1,4 @@
-# Codegen options
+# Codegen Options
 
 All of these options are passed to `rustc` via the `-C` flag, short for "codegen." You can see
 a version of this list for your exact compiler by running `rustc -C help`.

src/doc/rustc/src/command-line-arguments.md

@@ -1,4 +1,4 @@
-# Command-line arguments
+# Command-line Arguments
 
 Here's a list of command-line arguments to `rustc` and what they do.
 

src/doc/rustc/src/instrument-coverage.md

@@ -1,4 +1,4 @@
-# `instrument-coverage`
+# Instrumentation-based Code Coverage
 
 ## Introduction
 

src/doc/rustc/src/linker-plugin-lto.md

@@ -1,4 +1,4 @@
-# Linker-plugin-LTO
+# Linker-plugin-based LTO
 
 The `-C linker-plugin-lto` flag allows for deferring the LTO optimization
 to the actual linking step, which in turn allows for performing

src/doc/rustc/src/lints/levels.md

@@ -1,4 +1,4 @@
-# Lint levels
+# Lint Levels
 
 In `rustc`, lints are divided into five *levels*:
 

src/doc/rustc/src/lints/listing/allowed-by-default.md

@@ -1,3 +1,3 @@
-# Allowed-by-default lints
+# Allowed-by-default Lints
 
 This file is auto-generated by the lint-docs script.

src/doc/rustc/src/lints/listing/deny-by-default.md

@@ -1,3 +1,3 @@
-# Deny-by-default lints
+# Deny-by-default Lints
 
 This file is auto-generated by the lint-docs script.

src/doc/rustc/src/lints/listing/index.md

@@ -1,4 +1,4 @@
-# Lint listing
+# Lint Listing
 
 This section lists out all of the lints, grouped by their default lint levels.
 

src/doc/rustc/src/lints/listing/warn-by-default.md

@@ -1,3 +1,3 @@
-# Warn-by-default lints
+# Warn-by-default Lints
 
 This file is auto-generated by the lint-docs script.

src/doc/rustc/src/platform-support/pc-windows-gnullvm.md

@@ -4,7 +4,7 @@
 
 Windows targets similar to `*-pc-windows-gnu` but using UCRT as the runtime and various LLVM tools/libraries instead of GCC/Binutils.
 
-Target triples avaiable so far:
+Target triples available so far:
 - `aarch64-pc-windows-gnullvm`
 - `x86_64-pc-windows-gnullvm`
 
@@ -26,7 +26,7 @@ Like with any other Windows target created binaries are in PE format.
 ## Building the target
 
 For cross-compilation I recommend using [llvm-mingw](https://github.com/mstorsjo/llvm-mingw) toolchain, one change that seems necessary beside configuring corss compilers is disabling experimental `m86k` target. Otherwise LLVM build fails with `multiple definition ...` errors.
-Native bootstrapping builds require rather fragile hacks until host artifacts are avaiable so I won't describe them here.
+Native bootstrapping builds require rather fragile hacks until host artifacts are available so I won't describe them here.
 
 ## Building Rust programs
 

src/doc/rustc/src/profile-guided-optimization.md

@@ -1,4 +1,4 @@
-# Profile Guided Optimization
+# Profile-guided Optimization
 
 `rustc` supports doing profile-guided optimization (PGO).
 This chapter describes what PGO is, what it is good for, and how it can be used.

src/test/ui/const-generics/issues/issue-83249.stderr

@@ -5,6 +5,12 @@ LL |     let _ = foo([0; 1]);
    |         -   ^^^ cannot infer type for type parameter `T` declared on the function `foo`
    |         |
    |         consider giving this pattern a type
+   |
+help: type parameter declared here
+  --> $DIR/issue-83249.rs:12:8
+   |
+LL | fn foo<T: Foo>(_: [u8; T::N]) -> T {
+   |        ^
 
 error: aborting due to previous error
 

src/test/ui/consts/issue-64662.stderr

@@ -3,12 +3,24 @@ error[E0282]: type annotations needed
    |
 LL |     A = foo(),
    |         ^^^ cannot infer type for type parameter `T` declared on the function `foo`
+   |
+help: type parameter declared here
+  --> $DIR/issue-64662.rs:6:14
+   |
+LL | const fn foo<T>() -> isize {
+   |              ^
 
 error[E0282]: type annotations needed
   --> $DIR/issue-64662.rs:3:9
    |
 LL |     B = foo(),
    |         ^^^ cannot infer type for type parameter `T` declared on the function `foo`
+   |
+help: type parameter declared here
+  --> $DIR/issue-64662.rs:6:14
+   |
+LL | const fn foo<T>() -> isize {
+   |              ^
 
 error: aborting due to 2 previous errors
 

src/test/ui/error-codes/E0401.stderr

@@ -37,6 +37,12 @@ error[E0282]: type annotations needed
    |
 LL |     bfnr(x);
    |     ^^^^ cannot infer type for type parameter `U` declared on the function `bfnr`
+   |
+help: type parameter declared here
+  --> $DIR/E0401.rs:4:13
+   |
+LL |     fn bfnr<U, V: Baz<U>, W: Fn()>(y: T) {
+   |             ^
 
 error: aborting due to 4 previous errors
 

src/test/ui/inference/ambiguous_type_parameter.rs

@@ -0,0 +1,17 @@
+use std::collections::HashMap;
+
+trait Store<K, V> {
+    fn get_raw(&self, key: &K) -> Option<()>;
+}
+
+struct InMemoryStore;
+
+impl<K> Store<String, HashMap<K, String>> for InMemoryStore {
+    fn get_raw(&self, key: &String) -> Option<()> {
+        None
+    }
+}
+
+fn main() {
+    InMemoryStore.get_raw(&String::default()); //~ ERROR type annotations needed
+}

src/test/ui/inference/ambiguous_type_parameter.stderr

@@ -0,0 +1,15 @@
+error[E0282]: type annotations needed
+  --> $DIR/ambiguous_type_parameter.rs:16:19
+   |
+LL |     InMemoryStore.get_raw(&String::default());
+   |                   ^^^^^^^ cannot infer type for type parameter `K`
+   |
+help: type parameter declared here
+  --> $DIR/ambiguous_type_parameter.rs:9:6
+   |
+LL | impl<K> Store<String, HashMap<K, String>> for InMemoryStore {
+   |      ^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0282`.