Merge from rustc

41 files changed, 532 insertions, 326 deletions

diff --git a/src/bootstrap/src/core/build_steps/llvm.rs b/src/bootstrap/src/core/build_steps/llvm.rs
index 20a4d1a1515..2b7703000cb 100644
--- a/src/bootstrap/src/core/build_steps/llvm.rs
+++ b/src/bootstrap/src/core/build_steps/llvm.rs
@@ -443,23 +443,26 @@ impl Step for Llvm {
         // See https://github.com/rust-lang/rust/pull/50104
         cfg.define("LLVM_ENABLE_LIBXML2", "OFF");
 
-        if !enabled_llvm_projects.is_empty() {
-            enabled_llvm_projects.sort();
-            enabled_llvm_projects.dedup();
-            cfg.define("LLVM_ENABLE_PROJECTS", enabled_llvm_projects.join(";"));
-        }
-
         let mut enabled_llvm_runtimes = Vec::new();
 
         if helpers::forcing_clang_based_tests() {
             enabled_llvm_runtimes.push("compiler-rt");
         }
 
+        // This is an experimental flag, which likely builds more than necessary.
+        // We will optimize it when we get closer to releasing it on nightly.
         if builder.config.llvm_offload {
             enabled_llvm_runtimes.push("offload");
             //FIXME(ZuseZ4): LLVM intends to drop the offload dependency on openmp.
             //Remove this line once they achieved it.
             enabled_llvm_runtimes.push("openmp");
+            enabled_llvm_projects.push("compiler-rt");
+        }
+
+        if !enabled_llvm_projects.is_empty() {
+            enabled_llvm_projects.sort();
+            enabled_llvm_projects.dedup();
+            cfg.define("LLVM_ENABLE_PROJECTS", enabled_llvm_projects.join(";"));
         }
 
         if !enabled_llvm_runtimes.is_empty() {
diff --git a/src/bootstrap/src/lib.rs b/src/bootstrap/src/lib.rs
index cfb968f79ba..07772b8932d 100644
--- a/src/bootstrap/src/lib.rs
+++ b/src/bootstrap/src/lib.rs
@@ -1795,11 +1795,12 @@ Executed at: {executed_at}"#,
             let now = t!(SystemTime::now().duration_since(SystemTime::UNIX_EPOCH));
             let _ = fs::rename(dst, format!("{}-{}", dst.display(), now.as_nanos()));
         }
-        let metadata = t!(src.symlink_metadata(), format!("src = {}", src.display()));
+        let mut metadata = t!(src.symlink_metadata(), format!("src = {}", src.display()));
         let mut src = src.to_path_buf();
         if metadata.file_type().is_symlink() {
             if dereference_symlinks {
                 src = t!(fs::canonicalize(src));
+                metadata = t!(fs::metadata(&src), format!("target = {}", src.display()));
             } else {
                 let link = t!(fs::read_link(src));
                 t!(self.symlink_file(link, dst));
diff --git a/src/ci/docker/host-x86_64/dist-x86_64-linux/Dockerfile b/src/ci/docker/host-x86_64/dist-x86_64-linux/Dockerfile
index bedf45c8630..44f6a8d2a15 100644
--- a/src/ci/docker/host-x86_64/dist-x86_64-linux/Dockerfile
+++ b/src/ci/docker/host-x86_64/dist-x86_64-linux/Dockerfile
@@ -96,14 +96,13 @@ ENV RUST_CONFIGURE_ARGS \
       --set rust.lto=thin \
       --set rust.codegen-units=1
 
-# Note that `rust.debug` is set to true *only* for `opt-dist`
-ENV SCRIPT python3 ../x.py build --set rust.debug=true opt-dist && \
-    ./build/$HOSTS/stage0-tools-bin/opt-dist linux-ci -- python3 ../x.py dist \
-    --host $HOSTS --target $HOSTS \
-    --include-default-paths \
-    build-manifest bootstrap && \
-    # Use GCC for building GCC, as it seems to behave badly when built with Clang
-    CC=/rustroot/bin/cc CXX=/rustroot/bin/c++ python3 ../x.py dist gcc
+ARG SCRIPT_ARG
+
+COPY host-x86_64/dist-x86_64-linux/dist.sh /scripts/
+COPY host-x86_64/dist-x86_64-linux/dist-alt.sh /scripts/
+
+ENV SCRIPT /scripts/${SCRIPT_ARG}
+
 ENV CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER=clang
 
 # This is the only builder which will create source tarballs
diff --git a/src/ci/docker/host-x86_64/dist-x86_64-linux/dist-alt.sh b/src/ci/docker/host-x86_64/dist-x86_64-linux/dist-alt.sh
new file mode 100755
index 00000000000..8e756c32431
--- /dev/null
+++ b/src/ci/docker/host-x86_64/dist-x86_64-linux/dist-alt.sh
@@ -0,0 +1,8 @@
+#!/bin/bash
+
+set -eux
+
+python3 ../x.py dist \
+    --host $HOSTS --target $HOSTS \
+    --include-default-paths \
+    build-manifest bootstrap
diff --git a/src/ci/docker/host-x86_64/dist-x86_64-linux/dist.sh b/src/ci/docker/host-x86_64/dist-x86_64-linux/dist.sh
new file mode 100755
index 00000000000..064ac5b0a5e
--- /dev/null
+++ b/src/ci/docker/host-x86_64/dist-x86_64-linux/dist.sh
@@ -0,0 +1,13 @@
+#!/bin/bash
+
+set -eux
+
+python3 ../x.py build --set rust.debug=true opt-dist
+
+./build/$HOSTS/stage0-tools-bin/opt-dist linux-ci -- python3 ../x.py dist \
+    --host $HOSTS --target $HOSTS \
+    --include-default-paths \
+    build-manifest bootstrap
+
+# Use GCC for building GCC, as it seems to behave badly when built with Clang
+CC=/rustroot/bin/cc CXX=/rustroot/bin/c++ python3 ../x.py dist gcc
diff --git a/src/ci/github-actions/jobs.yml b/src/ci/github-actions/jobs.yml
index d59e440fb68..b6b2792d0ec 100644
--- a/src/ci/github-actions/jobs.yml
+++ b/src/ci/github-actions/jobs.yml
@@ -10,6 +10,10 @@ runners:
     free_disk: true
     <<: *base-job
 
+  - &job-linux-4c-largedisk
+    os: ubuntu-24.04-4core-16gb
+    <<: *base-job
+
   - &job-linux-8c
     os: ubuntu-24.04-8core-32gb
     <<: *base-job
@@ -105,6 +109,15 @@ envs:
   pr:
     PR_CI_JOB: 1
 
+jobs:
+  dist-x86_64-linux: &job-dist-x86_64-linux
+    name: dist-x86_64-linux
+    env:
+      CODEGEN_BACKENDS: llvm,cranelift
+      DOCKER_SCRIPT: dist.sh
+    <<: *job-linux-36c-codebuild
+
+
 # Jobs that run on each push to a pull request (PR)
 # These jobs automatically inherit envs.pr, to avoid repeating
 # it in each job definition.
@@ -138,10 +151,7 @@ pr:
 # These jobs automatically inherit envs.try, to avoid repeating
 # it in each job definition.
 try:
-  - name: dist-x86_64-linux
-    env:
-      CODEGEN_BACKENDS: llvm,cranelift
-    <<: *job-linux-36c-codebuild
+  - <<: *job-dist-x86_64-linux
 
 # Main CI jobs that have to be green to merge a commit into master
 # These jobs automatically inherit envs.auto, to avoid repeating
@@ -234,16 +244,14 @@ auto:
   - name: dist-x86_64-illumos
     <<: *job-linux-4c
 
-  - name: dist-x86_64-linux
-    env:
-      CODEGEN_BACKENDS: llvm,cranelift
-    <<: *job-linux-36c-codebuild
+  - <<: *job-dist-x86_64-linux
 
   - name: dist-x86_64-linux-alt
     env:
       IMAGE: dist-x86_64-linux
       CODEGEN_BACKENDS: llvm,cranelift
-    <<: *job-linux-16c
+      DOCKER_SCRIPT: dist-alt.sh
+    <<: *job-linux-4c-largedisk
 
   - name: dist-x86_64-musl
     env:
diff --git a/src/doc/rustc-dev-guide/rust-version b/src/doc/rustc-dev-guide/rust-version
index b1e9eec529e..8b48bd518bd 100644
--- a/src/doc/rustc-dev-guide/rust-version
+++ b/src/doc/rustc-dev-guide/rust-version
@@ -1 +1 @@
-99e7c15e81385b38a8186b51edc4577d5d7b5bdd
+c68032fd4c442d275f4daa571ba19c076106b490
diff --git a/src/doc/rustc-dev-guide/src/autodiff/flags.md b/src/doc/rustc-dev-guide/src/autodiff/flags.md
index 946ae1d03ae..65287d9ba4c 100644
--- a/src/doc/rustc-dev-guide/src/autodiff/flags.md
+++ b/src/doc/rustc-dev-guide/src/autodiff/flags.md
@@ -16,7 +16,9 @@ LooseTypes // Risk incorrect derivatives instead of aborting when missing Type I
 ```
 
 <div class="warning">
+
 `LooseTypes` is often helpful to get rid of Enzyme errors stating `Can not deduce type of <X>` and to be able to run some code. But please keep in mind that this flag absolutely has the chance to cause incorrect gradients. Even worse, the gradients might be correct for certain input values, but not for others. So please create issues about such bugs and only use this flag temporarily while you wait for your bug to be fixed.
+
 </div>
 
 ### Benchmark flags
diff --git a/src/doc/rustc-dev-guide/src/coroutine-closures.md b/src/doc/rustc-dev-guide/src/coroutine-closures.md
index 04742d03c50..48cdba44a9f 100644
--- a/src/doc/rustc-dev-guide/src/coroutine-closures.md
+++ b/src/doc/rustc-dev-guide/src/coroutine-closures.md
@@ -1,6 +1,10 @@
+# Async closures/"coroutine-closures"
+
+<!-- toc -->
+
 Please read [RFC 3668](https://rust-lang.github.io/rfcs/3668-async-closures.html) to understand the general motivation of the feature. This is a very technical and somewhat "vertical" chapter; ideally we'd split this and sprinkle it across all the relevant chapters, but for the purposes of understanding async closures *holistically*, I've put this together all here in one chapter.
 
-# Coroutine-closures -- a technical deep dive
+## Coroutine-closures -- a technical deep dive
 
 Coroutine-closures are a generalization of async closures, being special syntax for closure expressions which return a coroutine, notably one that is allowed to capture from the closure's upvars.
 
@@ -8,9 +12,11 @@ For now, the only usable kind of coroutine-closure is the async closure, and sup
 
 As a consequence of the code being somewhat general, this document may flip between calling them "async closures" and "coroutine-closures". The future that is returned by the async closure will generally be called the "coroutine" or the "child coroutine".
 
-## HIR
+### HIR
 
-Async closures (and in the future, other coroutine flavors such as `gen`) are represented in HIR as a `hir::Closure` whose closure-kind is `ClosureKind::CoroutineClosure(_)`[^k1], which wraps an async block, which is also represented in HIR as a `hir::Closure`) and whose closure-kind is `ClosureKind::Closure(CoroutineKind::Desugared(_, CoroutineSource::Closure))`[^k2].
+Async closures (and in the future, other coroutine flavors such as `gen`) are represented in HIR as a `hir::Closure`.
+The closure-kind of the `hir::Closure` is `ClosureKind::CoroutineClosure(_)`[^k1], which wraps an async block, which is also represented in HIR as a `hir::Closure`.
+The closure-kind of the async block is `ClosureKind::Closure(CoroutineKind::Desugared(_, CoroutineSource::Closure))`[^k2].
 
 [^k1]: <https://github.com/rust-lang/rust/blob/5ca0e9fa9b2f92b463a0a2b0b34315e09c0b7236/compiler/rustc_ast_lowering/src/expr.rs#L1147>
 
@@ -24,7 +30,7 @@ Like `async fn`, when lowering an async closure's body, we need to unconditional
 
 [^l3]: <https://github.com/rust-lang/rust/blob/5ca0e9fa9b2f92b463a0a2b0b34315e09c0b7236/compiler/rustc_hir_typeck/src/upvar.rs#L250-L256>
 
-## `rustc_middle::ty` Representation
+### `rustc_middle::ty` Representation
 
 For the purposes of keeping the implementation mostly future-compatible (i.e. with gen `|| {}` and `async gen || {}`), most of this section calls async closures "coroutine-closures".
 
@@ -72,7 +78,7 @@ To most easily construct the `Coroutine` that a coroutine-closure returns, you c
 
 Most of the args to that function will be components that you can get out of the `CoroutineArgs`, except for the `goal_kind: ClosureKind` which controls which flavor of coroutine to return based off of the `ClosureKind` passed in -- i.e. it will prepare the by-ref coroutine if `ClosureKind::Fn | ClosureKind::FnMut`, and the by-move coroutine if `ClosureKind::FnOnce`.
 
-## Trait Hierarchy
+### Trait Hierarchy
 
 We introduce a parallel hierarchy of `Fn*` traits that are implemented for . The motivation for the introduction was covered in a blog post: [Async Closures](https://hackmd.io/@compiler-errors/async-closures).
 
@@ -98,11 +104,11 @@ We mention above that "regular" callable types can implement `AsyncFn*`, but the
 
 See the "follow-up: when do..." section below for an elaborated answer. The full answer describes a pretty interesting and hopefully thorough heuristic that is used to ensure that most async closures "just work".
 
-## Tale of two bodies...
+### Tale of two bodies...
 
 When async closures are called with `AsyncFn`/`AsyncFnMut`, they return a coroutine that borrows from the closure. However, when they are called via `AsyncFnOnce`, we consume that closure, and cannot return a coroutine that borrows from data that is now dropped.
 
-To work around around this limitation, we synthesize a separate by-move MIR body for calling `AsyncFnOnce::call_once` on a coroutine-closure that can be called by-ref.
+To work around this limitation, we synthesize a separate by-move MIR body for calling `AsyncFnOnce::call_once` on a coroutine-closure that can be called by-ref.
 
 This body operates identically to the "normal" coroutine returned from calling the coroutine-closure, except for the fact that it has a different set of upvars, since we must *move* the captures from the parent coroutine-closure into the child coroutine.
 
@@ -120,7 +126,7 @@ Since we've synthesized a new def id, this query is also responsible for feeding
 
 [^b3]: <https://github.com/rust-lang/rust/blob/5ca0e9fa9b2f92b463a0a2b0b34315e09c0b7236/compiler/rustc_mir_transform/src/lib.rs#L339-L342>
 
-## Closure signature inference
+### Closure signature inference
 
 The closure signature inference algorithm for async closures is a bit more complicated than the inference algorithm for "traditional" closures. Like closures, we iterate through all of the clauses that may be relevant (for the expectation type passed in)[^deduce1].
 
@@ -173,7 +179,7 @@ s.as_bytes();
 
 So *instead*, we use this alias (in this case, a projection: `AsyncFnKindHelper::Upvars<'env, ...>`) to delay the computation of the *tupled upvars* and give us something to put in its place, while still allowing us to return a `TyKind::Coroutine` (which is a rigid type) and we may successfully confirm the built-in traits we need (in our case, `Future`), since the `Future` implementation doesn't depend on the upvars at all.
 
-## Upvar analysis
+### Upvar analysis
 
 By and large, the upvar analysis for coroutine-closures and their child coroutines proceeds like normal upvar analysis. However, there are several interesting bits that happen to account for async closures' special natures:
 
@@ -262,7 +268,7 @@ let c = async || {
 
 If either of these cases apply, then we should capture the borrow with the lifetime of the parent coroutine-closure's env. Luckily, if this function is not correct, then the program is not unsound, since we still borrowck and validate the choices made from this function -- the only side-effect is that the user may receive unnecessary borrowck errors.
 
-## Instance resolution
+### Instance resolution
 
 If a coroutine-closure has a closure-kind of `FnOnce`, then its `AsyncFnOnce::call_once` and `FnOnce::call_once` implementations resolve to the coroutine-closure's body[^res1], and the `Future::poll` of the coroutine that gets returned resolves to the body of the child closure.
 
@@ -282,7 +288,7 @@ This is represented by the `ConstructCoroutineInClosureShim`[^i1]. The `receiver
 
 [^i3]: <https://github.com/rust-lang/rust/blob/07cbbdd69363da97075650e9be24b78af0bcdd23/compiler/rustc_middle/src/ty/instance.rs#L841>
 
-## Borrow-checking
+### Borrow-checking
 
 It turns out that borrow-checking async closures is pretty straightforward. After adding a new `DefiningTy::CoroutineClosure`[^bck1] variant, and teaching borrowck how to generate the signature of the coroutine-closure[^bck2], borrowck proceeds totally fine.
 
diff --git a/src/doc/rustc-dev-guide/src/normalization.md b/src/doc/rustc-dev-guide/src/normalization.md
index 9705b1a244a..eb0962a4122 100644
--- a/src/doc/rustc-dev-guide/src/normalization.md
+++ b/src/doc/rustc-dev-guide/src/normalization.md
@@ -265,13 +265,13 @@ Another problem was that it was not possible to normalize `ParamEnv`s correctly
 
 Given a type such as `for<'a> fn(<?x as Trait<'a>::Assoc>)`, it is not possible to correctly handle this with the old solver's approach to normalization.
 
-If we were to normalize it to `for<'a> fn(?y)` and register a goal to normalize `for<'a> <?x as Trait<'a>>::Assoc -> ?y`, this would result in errors in cases where `<?x as Trait<'a>>::Assoc` normalized to `&'a u32`. The inference variable `?y` would be in a lower [universe][universes] than the placeholders made when instantiating the `for<'a>` binder.
+If we were to normalize it to `for<'a> fn(?y)` and register a goal to normalize `for<'a> <?x as Trait<'a>>::Assoc -> ?y`, this would result in errors in cases where `<?x as Trait<'a>>::Assoc` normalized to `&'a u32`. The inference variable `?y` would be in a lower [universe] than the placeholders made when instantiating the `for<'a>` binder.
 
 Leaving the alias unnormalized would also be wrong as the old solver expects all aliases to be rigid. This was a soundness bug before the new solver was stabilized in coherence: [relating projection substs is unsound during coherence](https://github.com/rust-lang/rust/issues/102048).
 
 Ultimately this means that it is not always possible to ensure all aliases inside of a value are rigid.
 
-[universes]: https://rustc-dev-guide.rust-lang.org/borrow_check/region_inference/placeholders_and_universes.html#what-is-a-universe
+[universe]: borrow_check/region_inference/placeholders_and_universes.md#what-is-a-universe
 [deeply_normalize]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_trait_selection/traits/normalize/trait.NormalizeExt.html#tymethod.deeply_normalize
 
 ## Handling uses of diverging aliases
diff --git a/src/doc/rustc-dev-guide/src/tests/ci.md b/src/doc/rustc-dev-guide/src/tests/ci.md
index ef3f4c7070c..96e4edc17a5 100644
--- a/src/doc/rustc-dev-guide/src/tests/ci.md
+++ b/src/doc/rustc-dev-guide/src/tests/ci.md
@@ -186,9 +186,11 @@ Note that if you start the default try job using `@bors try`, it will skip build
 Multiple try builds can execute concurrently across different PRs.
 
 <div class="warning">
-bors identify try jobs by commit hash. This means that if you have two PRs
+
+Bors identifies try jobs by commit hash. This means that if you have two PRs
 containing the same (latest) commits, running `@bors try` will result in the
 *same* try job and it really confuses `bors`. Please refrain from doing so.
+
 </div>
 
 [rustc-perf]: https://github.com/rust-lang/rustc-perf
diff --git a/src/doc/rustc-dev-guide/src/tests/compiletest.md b/src/doc/rustc-dev-guide/src/tests/compiletest.md
index e1b23748de3..ee06ca3b698 100644
--- a/src/doc/rustc-dev-guide/src/tests/compiletest.md
+++ b/src/doc/rustc-dev-guide/src/tests/compiletest.md
@@ -438,7 +438,9 @@ To work around this when working on a particular test, temporarily create a
 with these contents:
 
 <div class="warning">
+
 Be careful not to add this `Cargo.toml` or its `Cargo.lock` to your actual PR!
+
 </div>
 
 ```toml
diff --git a/src/doc/rustc-dev-guide/src/tests/directives.md b/src/doc/rustc-dev-guide/src/tests/directives.md
index 8a862417b0d..2dff21ed61c 100644
--- a/src/doc/rustc-dev-guide/src/tests/directives.md
+++ b/src/doc/rustc-dev-guide/src/tests/directives.md
@@ -248,11 +248,13 @@ ignoring debuggers.
 | `no-prefer-dynamic` | Don't use `-C prefer-dynamic`, don't build as a dylib via a `--crate-type=dylib` preset flag | `ui`, `crashes`           | N/A                                                                                        |
 
 <div class="warning">
+
 Tests (outside of `run-make`) that want to use incremental tests not in the
 incremental test-suite must not pass `-C incremental` via `compile-flags`, and
 must instead use the `//@ incremental` directive.
 
 Consider writing the test as a proper incremental test instead.
+
 </div>
 
 ### Rustdoc
diff --git a/src/doc/rustc-dev-guide/src/tests/minicore.md b/src/doc/rustc-dev-guide/src/tests/minicore.md
index 507b259e027..def9aaf8733 100644
--- a/src/doc/rustc-dev-guide/src/tests/minicore.md
+++ b/src/doc/rustc-dev-guide/src/tests/minicore.md
@@ -7,9 +7,11 @@ ui/codegen/assembly test suites. It provides `core` stubs for tests that need to
 build for cross-compiled targets but do not need/want to run.
 
 <div class="warning">
+
 Please note that [`minicore`] is only intended for `core` items, and explicitly
 **not** `std` or `alloc` items because `core` items are applicable to a wider
 range of tests.
+
 </div>
 
 A test can use [`minicore`] by specifying the `//@ add-core-stubs` directive.
diff --git a/src/doc/rustc-dev-guide/src/tests/running.md b/src/doc/rustc-dev-guide/src/tests/running.md
index 73c38736812..6526fe9c235 100644
--- a/src/doc/rustc-dev-guide/src/tests/running.md
+++ b/src/doc/rustc-dev-guide/src/tests/running.md
@@ -8,6 +8,7 @@ development because it takes a really long time. For local development, see the
 subsection after on how to run a subset of tests.
 
 <div class="warning">
+
 Running plain `./x test` will build the stage 1 compiler and then run the whole
 test suite. This not only include `tests/`, but also `library/`, `compiler/`,
 `src/tools/` package tests and more.
@@ -16,6 +17,7 @@ You usually only want to run a subset of the test suites (or even a smaller set
 of tests than that) which you expect will exercise your changes. PR CI exercises
 a subset of test collections, and merge queue CI will exercise all of the test
 collection.
+
 </div>
 
 ```text
@@ -116,8 +118,10 @@ By listing which test suites you want to run,
 you avoid having to run tests for components you did not change at all.
 
 <div class="warning">
+
 Note that bors only runs the tests with the full stage 2 build; therefore, while
 the tests **usually** work fine with stage 1, there are some limitations.
+
 </div>
 
 ### Run all tests using a stage 2 compiler
diff --git a/src/rustdoc-json-types/Cargo.toml b/src/rustdoc-json-types/Cargo.toml
index 14ff1d08816..a38d34ef0e7 100644
--- a/src/rustdoc-json-types/Cargo.toml
+++ b/src/rustdoc-json-types/Cargo.toml
@@ -10,7 +10,8 @@ path = "lib.rs"
 default = ["rustc-hash"]
 
 [dependencies]
-serde = { version = "1.0", features = ["derive"] }
+serde = "1.0"
+serde_derive = "1.0"
 rustc-hash = { version = "2.0", optional = true }
 
 [dev-dependencies]
diff --git a/src/rustdoc-json-types/lib.rs b/src/rustdoc-json-types/lib.rs
index f1c375bd2fe..8a3ab6f8640 100644
--- a/src/rustdoc-json-types/lib.rs
+++ b/src/rustdoc-json-types/lib.rs
@@ -21,7 +21,7 @@ use std::path::PathBuf;
 
 #[cfg(feature = "rustc-hash")]
 use rustc_hash::FxHashMap as HashMap;
-use serde::{Deserialize, Serialize};
+use serde_derive::{Deserialize, Serialize};
 
 pub type FxHashMap<K, V> = HashMap<K, V>; // re-export for use in src/librustdoc
 
diff --git a/src/tools/clippy/tests/ui/explicit_iter_loop.fixed b/src/tools/clippy/tests/ui/explicit_iter_loop.fixed
index f246ec61800..bffa1c4cf40 100644
--- a/src/tools/clippy/tests/ui/explicit_iter_loop.fixed
+++ b/src/tools/clippy/tests/ui/explicit_iter_loop.fixed
@@ -77,11 +77,11 @@ fn main() {
 
     struct NoIntoIter();
     impl NoIntoIter {
-        fn iter(&self) -> slice::Iter<u8> {
+        fn iter(&self) -> slice::Iter<'_, u8> {
             unimplemented!()
         }
 
-        fn iter_mut(&mut self) -> slice::IterMut<u8> {
+        fn iter_mut(&mut self) -> slice::IterMut<'_, u8> {
             unimplemented!()
         }
     }
diff --git a/src/tools/clippy/tests/ui/explicit_iter_loop.rs b/src/tools/clippy/tests/ui/explicit_iter_loop.rs
index 35f4fb7097d..6a5a3dd00ba 100644
--- a/src/tools/clippy/tests/ui/explicit_iter_loop.rs
+++ b/src/tools/clippy/tests/ui/explicit_iter_loop.rs
@@ -77,11 +77,11 @@ fn main() {
 
     struct NoIntoIter();
     impl NoIntoIter {
-        fn iter(&self) -> slice::Iter<u8> {
+        fn iter(&self) -> slice::Iter<'_, u8> {
             unimplemented!()
         }
 
-        fn iter_mut(&mut self) -> slice::IterMut<u8> {
+        fn iter_mut(&mut self) -> slice::IterMut<'_, u8> {
             unimplemented!()
         }
     }
diff --git a/src/tools/clippy/tests/ui/iter_next_loop.rs b/src/tools/clippy/tests/ui/iter_next_loop.rs
index 8e62ed963b9..969c51006af 100644
--- a/src/tools/clippy/tests/ui/iter_next_loop.rs
+++ b/src/tools/clippy/tests/ui/iter_next_loop.rs
@@ -8,7 +8,7 @@ fn main() {
 
     struct Unrelated(&'static [u8]);
     impl Unrelated {
-        fn next(&self) -> std::slice::Iter<u8> {
+        fn next(&self) -> std::slice::Iter<'_, u8> {
             self.0.iter()
         }
     }
diff --git a/src/tools/clippy/tests/ui/iter_not_returning_iterator.rs b/src/tools/clippy/tests/ui/iter_not_returning_iterator.rs
index 5c8c8eb4a43..d2497ed4330 100644
--- a/src/tools/clippy/tests/ui/iter_not_returning_iterator.rs
+++ b/src/tools/clippy/tests/ui/iter_not_returning_iterator.rs
@@ -71,7 +71,7 @@ impl S {
 
 struct S2([u8]);
 impl S2 {
-    fn iter(&self) -> core::slice::Iter<u8> {
+    fn iter(&self) -> core::slice::Iter<'_, u8> {
         self.0.iter()
     }
 }
diff --git a/src/tools/clippy/tests/ui/methods.rs b/src/tools/clippy/tests/ui/methods.rs
index 2f4004181f6..f73fe288b0f 100644
--- a/src/tools/clippy/tests/ui/methods.rs
+++ b/src/tools/clippy/tests/ui/methods.rs
@@ -49,7 +49,7 @@ struct Lt2<'a> {
 
 impl<'a> Lt2<'a> {
     // The lifetime is different, but that’s irrelevant; see issue #734.
-    pub fn new(s: &str) -> Lt2 {
+    pub fn new(s: &str) -> Lt2<'_> {
         unimplemented!()
     }
 }
diff --git a/src/tools/clippy/tests/ui/needless_lifetimes.fixed b/src/tools/clippy/tests/ui/needless_lifetimes.fixed
index e9d811986aa..ceea4480d0d 100644
--- a/src/tools/clippy/tests/ui/needless_lifetimes.fixed
+++ b/src/tools/clippy/tests/ui/needless_lifetimes.fixed
@@ -10,7 +10,7 @@
     clippy::unnecessary_wraps,
     dyn_drop,
     clippy::get_first,
-    elided_named_lifetimes
+    mismatched_lifetime_syntaxes,
 )]
 
 extern crate proc_macros;
diff --git a/src/tools/clippy/tests/ui/needless_lifetimes.rs b/src/tools/clippy/tests/ui/needless_lifetimes.rs
index 0b6eb9755b9..8432f9e6d2f 100644
--- a/src/tools/clippy/tests/ui/needless_lifetimes.rs
+++ b/src/tools/clippy/tests/ui/needless_lifetimes.rs
@@ -10,7 +10,7 @@
     clippy::unnecessary_wraps,
     dyn_drop,
     clippy::get_first,
-    elided_named_lifetimes
+    mismatched_lifetime_syntaxes,
 )]
 
 extern crate proc_macros;
diff --git a/src/tools/clippy/tests/ui/ptr_arg.rs b/src/tools/clippy/tests/ui/ptr_arg.rs
index 2d77bf06ff9..65f3f05d6cb 100644
--- a/src/tools/clippy/tests/ui/ptr_arg.rs
+++ b/src/tools/clippy/tests/ui/ptr_arg.rs
@@ -312,7 +312,7 @@ mod issue_9218 {
 
     // Inferred to be `&'a str`, afaik.
     fn cow_good_ret_ty<'a>(input: &'a Cow<'a, str>) -> &str {
-        //~^ ERROR: elided lifetime has a name
+        //~^ ERROR: lifetime flowing from input to output with different syntax
         todo!()
     }
 }
diff --git a/src/tools/clippy/tests/ui/ptr_arg.stderr b/src/tools/clippy/tests/ui/ptr_arg.stderr
index 741e60cbd74..600343754e1 100644
--- a/src/tools/clippy/tests/ui/ptr_arg.stderr
+++ b/src/tools/clippy/tests/ui/ptr_arg.stderr
@@ -1,12 +1,3 @@
-error: elided lifetime has a name
-  --> tests/ui/ptr_arg.rs:314:56
-   |
-LL |     fn cow_good_ret_ty<'a>(input: &'a Cow<'a, str>) -> &str {
-   |                        -- lifetime `'a` declared here  ^ this elided lifetime gets resolved as `'a`
-   |
-   = note: `-D elided-named-lifetimes` implied by `-D warnings`
-   = help: to override `-D warnings` add `#[allow(elided_named_lifetimes)]`
-
 error: writing `&Vec` instead of `&[_]` involves a new object where a slice will do
   --> tests/ui/ptr_arg.rs:13:14
    |
@@ -240,5 +231,21 @@ error: writing `&String` instead of `&str` involves a new object where a slice w
 LL |     fn good(v1: &String, v2: &String) {
    |                              ^^^^^^^ help: change this to: `&str`
 
+error: lifetime flowing from input to output with different syntax can be confusing
+  --> tests/ui/ptr_arg.rs:314:36
+   |
+LL |     fn cow_good_ret_ty<'a>(input: &'a Cow<'a, str>) -> &str {
+   |                                    ^^     ^^           ---- the lifetime gets resolved as `'a`
+   |                                    |      |
+   |                                    |      these lifetimes flow to the output
+   |                                    these lifetimes flow to the output
+   |
+   = note: `-D mismatched-lifetime-syntaxes` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(mismatched_lifetime_syntaxes)]`
+help: one option is to consistently use `'a`
+   |
+LL |     fn cow_good_ret_ty<'a>(input: &'a Cow<'a, str>) -> &'a str {
+   |                                                         ++
+
 error: aborting due to 27 previous errors
 
diff --git a/src/tools/clippy/tests/ui/significant_drop_in_scrutinee.rs b/src/tools/clippy/tests/ui/significant_drop_in_scrutinee.rs
index 4f65a06680d..78fc365bd5b 100644
--- a/src/tools/clippy/tests/ui/significant_drop_in_scrutinee.rs
+++ b/src/tools/clippy/tests/ui/significant_drop_in_scrutinee.rs
@@ -191,7 +191,7 @@ struct CounterWrapper<'a> {
 }
 
 impl<'a> CounterWrapper<'a> {
-    fn new(counter: &Counter) -> CounterWrapper {
+    fn new(counter: &Counter) -> CounterWrapper<'_> {
         counter.i.fetch_add(1, Ordering::Relaxed);
         CounterWrapper { counter }
     }
@@ -204,7 +204,7 @@ impl<'a> Drop for CounterWrapper<'a> {
 }
 
 impl Counter {
-    fn temp_increment(&self) -> Vec<CounterWrapper> {
+    fn temp_increment(&self) -> Vec<CounterWrapper<'_>> {
         vec![CounterWrapper::new(self), CounterWrapper::new(self)]
     }
 }
@@ -480,7 +480,7 @@ impl StateWithBoxedMutexGuard {
     fn new() -> StateWithBoxedMutexGuard {
         StateWithBoxedMutexGuard { u: Mutex::new(42) }
     }
-    fn lock(&self) -> Box<MutexGuard<u64>> {
+    fn lock(&self) -> Box<MutexGuard<'_, u64>> {
         Box::new(self.u.lock().unwrap())
     }
 }
@@ -507,7 +507,7 @@ impl StateStringWithBoxedMutexGuard {
             s: Mutex::new("A String".to_owned()),
         }
     }
-    fn lock(&self) -> Box<MutexGuard<String>> {
+    fn lock(&self) -> Box<MutexGuard<'_, String>> {
         Box::new(self.s.lock().unwrap())
     }
 }
@@ -686,11 +686,11 @@ struct Guard<'a, T>(MutexGuard<'a, T>);
 struct Ref<'a, T>(&'a T);
 
 impl<'a, T> Guard<'a, T> {
-    fn guard(&self) -> &MutexGuard<T> {
+    fn guard(&self) -> &MutexGuard<'_, T> {
         &self.0
     }
 
-    fn guard_ref(&self) -> Ref<MutexGuard<T>> {
+    fn guard_ref(&self) -> Ref<'_, MutexGuard<'_, T>> {
         Ref(&self.0)
     }
 
diff --git a/src/tools/clippy/tests/ui/trivially_copy_pass_by_ref.fixed b/src/tools/clippy/tests/ui/trivially_copy_pass_by_ref.fixed
index af7d82130f0..1a07f119398 100644
--- a/src/tools/clippy/tests/ui/trivially_copy_pass_by_ref.fixed
+++ b/src/tools/clippy/tests/ui/trivially_copy_pass_by_ref.fixed
@@ -41,6 +41,7 @@ fn good_return_explicit_lt_ref<'a>(foo: &'a Foo) -> &'a u32 {
     &foo.0
 }
 
+#[allow(mismatched_lifetime_syntaxes)]
 fn good_return_implicit_lt_struct(foo: &Foo) -> FooRef {
     FooRef { foo }
 }
diff --git a/src/tools/clippy/tests/ui/trivially_copy_pass_by_ref.rs b/src/tools/clippy/tests/ui/trivially_copy_pass_by_ref.rs
index 00e11a1ea28..07b1842bbf8 100644
--- a/src/tools/clippy/tests/ui/trivially_copy_pass_by_ref.rs
+++ b/src/tools/clippy/tests/ui/trivially_copy_pass_by_ref.rs
@@ -41,6 +41,7 @@ fn good_return_explicit_lt_ref<'a>(foo: &'a Foo) -> &'a u32 {
     &foo.0
 }
 
+#[allow(mismatched_lifetime_syntaxes)]
 fn good_return_implicit_lt_struct(foo: &Foo) -> FooRef {
     FooRef { foo }
 }
diff --git a/src/tools/clippy/tests/ui/trivially_copy_pass_by_ref.stderr b/src/tools/clippy/tests/ui/trivially_copy_pass_by_ref.stderr
index f101ac5ccd6..36247d3fe0b 100644
--- a/src/tools/clippy/tests/ui/trivially_copy_pass_by_ref.stderr
+++ b/src/tools/clippy/tests/ui/trivially_copy_pass_by_ref.stderr
@@ -1,5 +1,5 @@
 error: this argument (N byte) is passed by reference, but would be more efficient if passed by value (limit: N byte)
-  --> tests/ui/trivially_copy_pass_by_ref.rs:53:11
+  --> tests/ui/trivially_copy_pass_by_ref.rs:54:11
    |
 LL | fn bad(x: &u32, y: &Foo, z: &Baz) {}
    |           ^^^^ help: consider passing by value instead: `u32`
@@ -11,103 +11,103 @@ LL | #![deny(clippy::trivially_copy_pass_by_ref)]
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: this argument (N byte) is passed by reference, but would be more efficient if passed by value (limit: N byte)
-  --> tests/ui/trivially_copy_pass_by_ref.rs:53:20
+  --> tests/ui/trivially_copy_pass_by_ref.rs:54:20
    |
 LL | fn bad(x: &u32, y: &Foo, z: &Baz) {}
    |                    ^^^^ help: consider passing by value instead: `Foo`
 
 error: this argument (N byte) is passed by reference, but would be more efficient if passed by value (limit: N byte)
-  --> tests/ui/trivially_copy_pass_by_ref.rs:53:29
+  --> tests/ui/trivially_copy_pass_by_ref.rs:54:29
    |
 LL | fn bad(x: &u32, y: &Foo, z: &Baz) {}
    |                             ^^^^ help: consider passing by value instead: `Baz`
 
 error: this argument (N byte) is passed by reference, but would be more efficient if passed by value (limit: N byte)
-  --> tests/ui/trivially_copy_pass_by_ref.rs:63:12
+  --> tests/ui/trivially_copy_pass_by_ref.rs:64:12
    |
 LL |     fn bad(&self, x: &u32, y: &Foo, z: &Baz) {}
    |            ^^^^^ help: consider passing by value instead: `self`
 
 error: this argument (N byte) is passed by reference, but would be more efficient if passed by value (limit: N byte)
-  --> tests/ui/trivially_copy_pass_by_ref.rs:63:22
+  --> tests/ui/trivially_copy_pass_by_ref.rs:64:22
    |
 LL |     fn bad(&self, x: &u32, y: &Foo, z: &Baz) {}
    |                      ^^^^ help: consider passing by value instead: `u32`
 
 error: this argument (N byte) is passed by reference, but would be more efficient if passed by value (limit: N byte)
-  --> tests/ui/trivially_copy_pass_by_ref.rs:63:31
+  --> tests/ui/trivially_copy_pass_by_ref.rs:64:31
    |
 LL |     fn bad(&self, x: &u32, y: &Foo, z: &Baz) {}
    |                               ^^^^ help: consider passing by value instead: `Foo`
 
 error: this argument (N byte) is passed by reference, but would be more efficient if passed by value (limit: N byte)
-  --> tests/ui/trivially_copy_pass_by_ref.rs:63:40
+  --> tests/ui/trivially_copy_pass_by_ref.rs:64:40
    |
 LL |     fn bad(&self, x: &u32, y: &Foo, z: &Baz) {}
    |                                        ^^^^ help: consider passing by value instead: `Baz`
 
 error: this argument (N byte) is passed by reference, but would be more efficient if passed by value (limit: N byte)
-  --> tests/ui/trivially_copy_pass_by_ref.rs:69:16
+  --> tests/ui/trivially_copy_pass_by_ref.rs:70:16
    |
 LL |     fn bad2(x: &u32, y: &Foo, z: &Baz) {}
    |                ^^^^ help: consider passing by value instead: `u32`
 
 error: this argument (N byte) is passed by reference, but would be more efficient if passed by value (limit: N byte)
-  --> tests/ui/trivially_copy_pass_by_ref.rs:69:25
+  --> tests/ui/trivially_copy_pass_by_ref.rs:70:25
    |
 LL |     fn bad2(x: &u32, y: &Foo, z: &Baz) {}
    |                         ^^^^ help: consider passing by value instead: `Foo`
 
 error: this argument (N byte) is passed by reference, but would be more efficient if passed by value (limit: N byte)
-  --> tests/ui/trivially_copy_pass_by_ref.rs:69:34
+  --> tests/ui/trivially_copy_pass_by_ref.rs:70:34
    |
 LL |     fn bad2(x: &u32, y: &Foo, z: &Baz) {}
    |                                  ^^^^ help: consider passing by value instead: `Baz`
 
 error: this argument (N byte) is passed by reference, but would be more efficient if passed by value (limit: N byte)
-  --> tests/ui/trivially_copy_pass_by_ref.rs:74:35
+  --> tests/ui/trivially_copy_pass_by_ref.rs:75:35
    |
 LL |     fn bad_issue7518(self, other: &Self) {}
    |                                   ^^^^^ help: consider passing by value instead: `Self`
 
 error: this argument (N byte) is passed by reference, but would be more efficient if passed by value (limit: N byte)
-  --> tests/ui/trivially_copy_pass_by_ref.rs:87:16
+  --> tests/ui/trivially_copy_pass_by_ref.rs:88:16
    |
 LL |     fn bad2(x: &u32, y: &Foo, z: &Baz) {}
    |                ^^^^ help: consider passing by value instead: `u32`
 
 error: this argument (N byte) is passed by reference, but would be more efficient if passed by value (limit: N byte)
-  --> tests/ui/trivially_copy_pass_by_ref.rs:87:25
+  --> tests/ui/trivially_copy_pass_by_ref.rs:88:25
    |
 LL |     fn bad2(x: &u32, y: &Foo, z: &Baz) {}
    |                         ^^^^ help: consider passing by value instead: `Foo`
 
 error: this argument (N byte) is passed by reference, but would be more efficient if passed by value (limit: N byte)
-  --> tests/ui/trivially_copy_pass_by_ref.rs:87:34
+  --> tests/ui/trivially_copy_pass_by_ref.rs:88:34
    |
 LL |     fn bad2(x: &u32, y: &Foo, z: &Baz) {}
    |                                  ^^^^ help: consider passing by value instead: `Baz`
 
 error: this argument (N byte) is passed by reference, but would be more efficient if passed by value (limit: N byte)
-  --> tests/ui/trivially_copy_pass_by_ref.rs:94:33
+  --> tests/ui/trivially_copy_pass_by_ref.rs:95:33
    |
 LL |     fn trait_method(&self, foo: &Foo);
    |                                 ^^^^ help: consider passing by value instead: `Foo`
 
 error: this argument (N byte) is passed by reference, but would be more efficient if passed by value (limit: N byte)
-  --> tests/ui/trivially_copy_pass_by_ref.rs:132:21
+  --> tests/ui/trivially_copy_pass_by_ref.rs:133:21
    |
 LL |     fn foo_never(x: &i32) {
    |                     ^^^^ help: consider passing by value instead: `i32`
 
 error: this argument (N byte) is passed by reference, but would be more efficient if passed by value (limit: N byte)
-  --> tests/ui/trivially_copy_pass_by_ref.rs:138:15
+  --> tests/ui/trivially_copy_pass_by_ref.rs:139:15
    |
 LL |     fn foo(x: &i32) {
    |               ^^^^ help: consider passing by value instead: `i32`
 
 error: this argument (N byte) is passed by reference, but would be more efficient if passed by value (limit: N byte)
-  --> tests/ui/trivially_copy_pass_by_ref.rs:164:36
+  --> tests/ui/trivially_copy_pass_by_ref.rs:165:36
    |
 LL | fn unrelated_lifetimes<'a, 'b>(_x: &'a u32, y: &'b u32) -> &'b u32 {
    |                                    ^^^^^^^ help: consider passing by value instead: `u32`
diff --git a/src/tools/clippy/tests/ui/use_self.fixed b/src/tools/clippy/tests/ui/use_self.fixed
index f15e5e0a5bb..cccb6bffabb 100644
--- a/src/tools/clippy/tests/ui/use_self.fixed
+++ b/src/tools/clippy/tests/ui/use_self.fixed
@@ -69,7 +69,7 @@ mod lifetimes {
     impl<'a> Foo<'a> {
         // Cannot use `Self` as return type, because the function is actually `fn foo<'b>(s: &'b str) ->
         // Foo<'b>`
-        fn foo(s: &str) -> Foo {
+        fn foo(s: &str) -> Foo<'_> {
             Foo { foo_str: s }
         }
         // cannot replace with `Self`, because that's `Foo<'a>`
diff --git a/src/tools/clippy/tests/ui/use_self.rs b/src/tools/clippy/tests/ui/use_self.rs
index b6376938611..09288677aa7 100644
--- a/src/tools/clippy/tests/ui/use_self.rs
+++ b/src/tools/clippy/tests/ui/use_self.rs
@@ -69,7 +69,7 @@ mod lifetimes {
     impl<'a> Foo<'a> {
         // Cannot use `Self` as return type, because the function is actually `fn foo<'b>(s: &'b str) ->
         // Foo<'b>`
-        fn foo(s: &str) -> Foo {
+        fn foo(s: &str) -> Foo<'_> {
             Foo { foo_str: s }
         }
         // cannot replace with `Self`, because that's `Foo<'a>`
diff --git a/src/tools/jsondocck/src/config.rs b/src/tools/jsondocck/src/config.rs
index 9b3ba3f3fbe..6bef37c2259 100644
--- a/src/tools/jsondocck/src/config.rs
+++ b/src/tools/jsondocck/src/config.rs
@@ -4,7 +4,7 @@ use getopts::Options;
 pub struct Config {
     /// The directory documentation output was generated in
     pub doc_dir: String,
-    /// The file documentation was generated for, with docck commands to check
+    /// The file documentation was generated for, with docck directives to check
     pub template: String,
 }
 
diff --git a/src/tools/jsondocck/src/directive.rs b/src/tools/jsondocck/src/directive.rs
new file mode 100644
index 00000000000..fdb2fa6dbbe
--- /dev/null
+++ b/src/tools/jsondocck/src/directive.rs
@@ -0,0 +1,232 @@
+use std::borrow::Cow;
+
+use serde_json::Value;
+
+use crate::cache::Cache;
+
+#[derive(Debug)]
+pub struct Directive {
+    pub kind: DirectiveKind,
+    pub path: String,
+    pub lineno: usize,
+}
+
+#[derive(Debug)]
+pub enum DirectiveKind {
+    /// `//@ has <path>`
+    ///
+    /// Checks the path exists.
+    HasPath,
+
+    /// `//@ has <path> <value>`
+    ///
+    /// Check one thing at the path  is equal to the value.
+    HasValue { value: String },
+
+    /// `//@ !has <path>`
+    ///
+    /// Checks the path doesn't exist.
+    HasNotPath,
+
+    /// `//@ !has <path> <value>`
+    ///
+    /// Checks the path exists, but doesn't have the given value.
+    HasNotValue { value: String },
+
+    /// `//@ is <path> <value>`
+    ///
+    /// Check the path is the given value.
+    Is { value: String },
+
+    /// `//@ is <path> <value> <value>...`
+    ///
+    /// Check that the path matches to exactly every given value.
+    IsMany { values: Vec<String> },
+
+    /// `//@ !is <path> <value>`
+    ///
+    /// Check the path isn't the given value.
+    IsNot { value: String },
+
+    /// `//@ count <path> <value>`
+    ///
+    /// Check the path has the expected number of matches.
+    CountIs { expected: usize },
+
+    /// `//@ set <name> = <path>`
+    Set { variable: String },
+}
+
+impl DirectiveKind {
+    /// Returns both the kind and the path.
+    ///
+    /// Returns `None` if the directive isn't from jsondocck (e.g. from compiletest).
+    pub fn parse<'a>(
+        directive_name: &str,
+        negated: bool,
+        args: &'a [String],
+    ) -> Option<(Self, &'a str)> {
+        let kind = match (directive_name, negated) {
+            ("count", false) => {
+                assert_eq!(args.len(), 2);
+                let expected = args[1].parse().expect("invalid number for `count`");
+                Self::CountIs { expected }
+            }
+
+            ("ismany", false) => {
+                // FIXME: Make this >= 3, and migrate len(values)==1 cases to @is
+                assert!(args.len() >= 2, "Not enough args to `ismany`");
+                let values = args[1..].to_owned();
+                Self::IsMany { values }
+            }
+
+            ("is", false) => {
+                assert_eq!(args.len(), 2);
+                Self::Is { value: args[1].clone() }
+            }
+            ("is", true) => {
+                assert_eq!(args.len(), 2);
+                Self::IsNot { value: args[1].clone() }
+            }
+
+            ("set", false) => {
+                assert_eq!(args.len(), 3);
+                assert_eq!(args[1], "=");
+                return Some((Self::Set { variable: args[0].clone() }, &args[2]));
+            }
+
+            ("has", false) => match args {
+                [_path] => Self::HasPath,
+                [_path, value] => Self::HasValue { value: value.clone() },
+                _ => panic!("`//@ has` must have 2 or 3 arguments, but got {args:?}"),
+            },
+            ("has", true) => match args {
+                [_path] => Self::HasNotPath,
+                [_path, value] => Self::HasNotValue { value: value.clone() },
+                _ => panic!("`//@ !has` must have 2 or 3 arguments, but got {args:?}"),
+            },
+            // Ignore compiletest directives, like //@ edition
+            (_, false) if KNOWN_DIRECTIVE_NAMES.contains(&directive_name) => {
+                return None;
+            }
+            _ => {
+                panic!("Invalid directive `//@ {}{directive_name}`", if negated { "!" } else { "" })
+            }
+        };
+
+        Some((kind, &args[0]))
+    }
+}
+
+impl Directive {
+    /// Performs the actual work of ensuring a directive passes.
+    pub fn check(&self, cache: &mut Cache) -> Result<(), String> {
+        let matches = cache.select(&self.path);
+        match &self.kind {
+            DirectiveKind::HasPath => {
+                if matches.is_empty() {
+                    return Err("matched to no values".to_owned());
+                }
+            }
+            DirectiveKind::HasNotPath => {
+                if !matches.is_empty() {
+                    return Err(format!("matched to {matches:?}, but wanted no matches"));
+                }
+            }
+            DirectiveKind::HasValue { value } => {
+                let want_value = string_to_value(value, cache);
+                if !matches.contains(&want_value.as_ref()) {
+                    return Err(format!(
+                        "matched to {matches:?}, which didn't contain {want_value:?}"
+                    ));
+                }
+            }
+            DirectiveKind::HasNotValue { value } => {
+                let wantnt_value = string_to_value(value, cache);
+                if matches.contains(&wantnt_value.as_ref()) {
+                    return Err(format!(
+                        "matched to {matches:?}, which contains unwanted {wantnt_value:?}"
+                    ));
+                } else if matches.is_empty() {
+                    return Err(format!(
+                        "got no matches, but expected some matched (not containing {wantnt_value:?}"
+                    ));
+                }
+            }
+
+            DirectiveKind::Is { value } => {
+                let want_value = string_to_value(value, cache);
+                let matched = get_one(&matches)?;
+                if matched != want_value.as_ref() {
+                    return Err(format!("matched to {matched:?} but want {want_value:?}"));
+                }
+            }
+            DirectiveKind::IsNot { value } => {
+                let wantnt_value = string_to_value(value, cache);
+                let matched = get_one(&matches)?;
+                if matched == wantnt_value.as_ref() {
+                    return Err(format!("got value {wantnt_value:?}, but want anything else"));
+                }
+            }
+
+            DirectiveKind::IsMany { values } => {
+                // Serde json doesn't implement Ord or Hash for Value, so we must
+                // use a Vec here. While in theory that makes setwize equality
+                // O(n^2), in practice n will never be large enough to matter.
+                let expected_values =
+                    values.iter().map(|v| string_to_value(v, cache)).collect::<Vec<_>>();
+                if expected_values.len() != matches.len() {
+                    return Err(format!(
+                        "Expected {} values, but matched to {} values ({:?})",
+                        expected_values.len(),
+                        matches.len(),
+                        matches
+                    ));
+                };
+                for got_value in matches {
+                    if !expected_values.iter().any(|exp| &**exp == got_value) {
+                        return Err(format!("has match {got_value:?}, which was not expected",));
+                    }
+                }
+            }
+            DirectiveKind::CountIs { expected } => {
+                if *expected != matches.len() {
+                    return Err(format!(
+                        "matched to `{matches:?}` with length {}, but expected length {expected}",
+                        matches.len(),
+                    ));
+                }
+            }
+            DirectiveKind::Set { variable } => {
+                let value = get_one(&matches)?;
+                let r = cache.variables.insert(variable.to_owned(), value.clone());
+                assert!(r.is_none(), "name collision: {variable:?} is duplicated");
+            }
+        }
+
+        Ok(())
+    }
+}
+
+fn get_one<'a>(matches: &[&'a Value]) -> Result<&'a Value, String> {
+    match matches {
+        [] => Err("matched to no values".to_owned()),
+        [matched] => Ok(matched),
+        _ => Err(format!("matched to multiple values {matches:?}, but want exactly 1")),
+    }
+}
+
+// FIXME: This setup is temporary until we figure out how to improve this situation.
+//        See <https://github.com/rust-lang/rust/issues/125813#issuecomment-2141953780>.
+include!(concat!(env!("CARGO_MANIFEST_DIR"), "/../compiletest/src/directive-list.rs"));
+
+fn string_to_value<'a>(s: &str, cache: &'a Cache) -> Cow<'a, Value> {
+    if s.starts_with("$") {
+        Cow::Borrowed(&cache.variables.get(&s[1..]).unwrap_or_else(|| {
+            // FIXME(adotinthevoid): Show line number
+            panic!("No variable: `{}`. Current state: `{:?}`", &s[1..], cache.variables)
+        }))
+    } else {
+        Cow::Owned(serde_json::from_str(s).expect(&format!("Cannot convert `{}` to json", s)))
+    }
+}
diff --git a/src/tools/jsondocck/src/error.rs b/src/tools/jsondocck/src/error.rs
index 0a3e085b405..eb2932f7803 100644
--- a/src/tools/jsondocck/src/error.rs
+++ b/src/tools/jsondocck/src/error.rs
@@ -1,7 +1,7 @@
-use crate::Command;
+use crate::Directive;
 
 #[derive(Debug)]
 pub struct CkError {
     pub message: String,
-    pub command: Command,
+    pub directive: Directive,
 }
diff --git a/src/tools/jsondocck/src/main.rs b/src/tools/jsondocck/src/main.rs
index 65ad38da98b..d84be4d3a3a 100644
--- a/src/tools/jsondocck/src/main.rs
+++ b/src/tools/jsondocck/src/main.rs
@@ -1,17 +1,17 @@
-use std::borrow::Cow;
 use std::process::ExitCode;
 use std::sync::LazyLock;
 use std::{env, fs};
 
 use regex::{Regex, RegexBuilder};
-use serde_json::Value;
 
 mod cache;
 mod config;
+mod directive;
 mod error;
 
 use cache::Cache;
 use config::parse_config;
+use directive::{Directive, DirectiveKind};
 use error::CkError;
 
 fn main() -> ExitCode {
@@ -19,14 +19,14 @@ fn main() -> ExitCode {
 
     let mut failed = Vec::new();
     let mut cache = Cache::new(&config);
-    let Ok(commands) = get_commands(&config.template) else {
+    let Ok(directives) = get_directives(&config.template) else {
         eprintln!("Jsondocck failed for {}", &config.template);
         return ExitCode::FAILURE;
     };
 
-    for command in commands {
-        if let Err(message) = check_command(&command, &mut cache) {
-            failed.push(CkError { command, message });
+    for directive in directives {
+        if let Err(message) = directive.check(&mut cache) {
+            failed.push(CkError { directive, message });
         }
     }
 
@@ -34,130 +34,20 @@ fn main() -> ExitCode {
         ExitCode::SUCCESS
     } else {
         for i in failed {
-            eprintln!("{}:{}, command failed", config.template, i.command.lineno);
+            eprintln!("{}:{}, directive failed", config.template, i.directive.lineno);
             eprintln!("{}", i.message)
         }
         ExitCode::FAILURE
     }
 }
 
-#[derive(Debug)]
-pub struct Command {
-    kind: CommandKind,
-    path: String,
-    lineno: usize,
-}
-
-#[derive(Debug)]
-enum CommandKind {
-    /// `//@ has <path>`
-    ///
-    /// Checks the path exists.
-    HasPath,
-
-    /// `//@ has <path> <value>`
-    ///
-    /// Check one thing at the path  is equal to the value.
-    HasValue { value: String },
-
-    /// `//@ !has <path>`
-    ///
-    /// Checks the path doesn't exist.
-    HasNotPath,
-
-    /// `//@ !has <path> <value>`
-    ///
-    /// Checks the path exists, but doesn't have the given value.
-    HasNotValue { value: String },
-
-    /// `//@ is <path> <value>`
-    ///
-    /// Check the path is the given value.
-    Is { value: String },
-
-    /// `//@ is <path> <value> <value>...`
-    ///
-    /// Check that the path matches to exactly every given value.
-    IsMany { values: Vec<String> },
-
-    /// `//@ !is <path> <value>`
-    ///
-    /// Check the path isn't the given value.
-    IsNot { value: String },
-
-    /// `//@ count <path> <value>`
-    ///
-    /// Check the path has the expected number of matches.
-    CountIs { expected: usize },
-
-    /// `//@ set <name> = <path>`
-    Set { variable: String },
-}
-
-impl CommandKind {
-    /// Returns both the kind and the path.
-    ///
-    /// Returns `None` if the command isn't from jsondocck (e.g. from compiletest).
-    fn parse<'a>(command_name: &str, negated: bool, args: &'a [String]) -> Option<(Self, &'a str)> {
-        let kind = match (command_name, negated) {
-            ("count", false) => {
-                assert_eq!(args.len(), 2);
-                let expected = args[1].parse().expect("invalid number for `count`");
-                Self::CountIs { expected }
-            }
-
-            ("ismany", false) => {
-                // FIXME: Make this >= 3, and migrate len(values)==1 cases to @is
-                assert!(args.len() >= 2, "Not enough args to `ismany`");
-                let values = args[1..].to_owned();
-                Self::IsMany { values }
-            }
-
-            ("is", false) => {
-                assert_eq!(args.len(), 2);
-                Self::Is { value: args[1].clone() }
-            }
-            ("is", true) => {
-                assert_eq!(args.len(), 2);
-                Self::IsNot { value: args[1].clone() }
-            }
-
-            ("set", false) => {
-                assert_eq!(args.len(), 3);
-                assert_eq!(args[1], "=");
-                return Some((Self::Set { variable: args[0].clone() }, &args[2]));
-            }
-
-            ("has", false) => match args {
-                [_path] => Self::HasPath,
-                [_path, value] => Self::HasValue { value: value.clone() },
-                _ => panic!("`//@ has` must have 2 or 3 arguments, but got {args:?}"),
-            },
-            ("has", true) => match args {
-                [_path] => Self::HasNotPath,
-                [_path, value] => Self::HasNotValue { value: value.clone() },
-                _ => panic!("`//@ !has` must have 2 or 3 arguments, but got {args:?}"),
-            },
-
-            (_, false) if KNOWN_DIRECTIVE_NAMES.contains(&command_name) => {
-                return None;
-            }
-            _ => {
-                panic!("Invalid command `//@ {}{command_name}`", if negated { "!" } else { "" })
-            }
-        };
-
-        Some((kind, &args[0]))
-    }
-}
-
 static LINE_PATTERN: LazyLock<Regex> = LazyLock::new(|| {
     RegexBuilder::new(
         r#"
         ^\s*
         //@\s+
         (?P<negated>!?)
-        (?P<cmd>[A-Za-z0-9]+(?:-[A-Za-z0-9]+)*)
+        (?P<directive>[A-Za-z0-9]+(?:-[A-Za-z0-9]+)*)
         (?P<args>.*)$
     "#,
     )
@@ -180,16 +70,12 @@ static DEPRECATED_LINE_PATTERN: LazyLock<Regex> = LazyLock::new(|| {
 });
 
 fn print_err(msg: &str, lineno: usize) {
-    eprintln!("Invalid command: {} on line {}", msg, lineno)
+    eprintln!("Invalid directive: {} on line {}", msg, lineno)
 }
 
-// FIXME: This setup is temporary until we figure out how to improve this situation.
-//        See <https://github.com/rust-lang/rust/issues/125813#issuecomment-2141953780>.
-include!(concat!(env!("CARGO_MANIFEST_DIR"), "/../compiletest/src/directive-list.rs"));
-
-/// Get a list of commands from a file.
-fn get_commands(template: &str) -> Result<Vec<Command>, ()> {
-    let mut commands = Vec::new();
+/// Get a list of directives from a file.
+fn get_directives(template: &str) -> Result<Vec<Directive>, ()> {
+    let mut directives = Vec::new();
     let mut errors = false;
     let file = fs::read_to_string(template).unwrap();
 
@@ -197,7 +83,7 @@ fn get_commands(template: &str) -> Result<Vec<Command>, ()> {
         let lineno = lineno + 1;
 
         if DEPRECATED_LINE_PATTERN.is_match(line) {
-            print_err("Deprecated command syntax, replace `// @` with `//@ `", lineno);
+            print_err("Deprecated directive syntax, replace `// @` with `//@ `", lineno);
             errors = true;
             continue;
         }
@@ -215,115 +101,10 @@ fn get_commands(template: &str) -> Result<Vec<Command>, ()> {
             continue;
         };
 
-        if let Some((kind, path)) = CommandKind::parse(&cap["cmd"], negated, &args) {
-            commands.push(Command { kind, lineno, path: path.to_owned() })
+        if let Some((kind, path)) = DirectiveKind::parse(&cap["directive"], negated, &args) {
+            directives.push(Directive { kind, lineno, path: path.to_owned() })
         }
     }
 
-    if !errors { Ok(commands) } else { Err(()) }
-}
-
-/// Performs the actual work of ensuring a command passes.
-fn check_command(command: &Command, cache: &mut Cache) -> Result<(), String> {
-    let matches = cache.select(&command.path);
-    match &command.kind {
-        CommandKind::HasPath => {
-            if matches.is_empty() {
-                return Err("matched to no values".to_owned());
-            }
-        }
-        CommandKind::HasNotPath => {
-            if !matches.is_empty() {
-                return Err(format!("matched to {matches:?}, but wanted no matches"));
-            }
-        }
-        CommandKind::HasValue { value } => {
-            let want_value = string_to_value(value, cache);
-            if !matches.contains(&want_value.as_ref()) {
-                return Err(format!("matched to {matches:?}, which didn't contain {want_value:?}"));
-            }
-        }
-        CommandKind::HasNotValue { value } => {
-            let wantnt_value = string_to_value(value, cache);
-            if matches.contains(&wantnt_value.as_ref()) {
-                return Err(format!(
-                    "matched to {matches:?}, which contains unwanted {wantnt_value:?}"
-                ));
-            } else if matches.is_empty() {
-                return Err(format!(
-                    "got no matches, but expected some matched (not containing {wantnt_value:?}"
-                ));
-            }
-        }
-
-        CommandKind::Is { value } => {
-            let want_value = string_to_value(value, cache);
-            let matched = get_one(&matches)?;
-            if matched != want_value.as_ref() {
-                return Err(format!("matched to {matched:?} but want {want_value:?}"));
-            }
-        }
-        CommandKind::IsNot { value } => {
-            let wantnt_value = string_to_value(value, cache);
-            let matched = get_one(&matches)?;
-            if matched == wantnt_value.as_ref() {
-                return Err(format!("got value {wantnt_value:?}, but want anything else"));
-            }
-        }
-
-        CommandKind::IsMany { values } => {
-            // Serde json doesn't implement Ord or Hash for Value, so we must
-            // use a Vec here. While in theory that makes setwize equality
-            // O(n^2), in practice n will never be large enough to matter.
-            let expected_values =
-                values.iter().map(|v| string_to_value(v, cache)).collect::<Vec<_>>();
-            if expected_values.len() != matches.len() {
-                return Err(format!(
-                    "Expected {} values, but matched to {} values ({:?})",
-                    expected_values.len(),
-                    matches.len(),
-                    matches
-                ));
-            };
-            for got_value in matches {
-                if !expected_values.iter().any(|exp| &**exp == got_value) {
-                    return Err(format!("has match {got_value:?}, which was not expected",));
-                }
-            }
-        }
-        CommandKind::CountIs { expected } => {
-            if *expected != matches.len() {
-                return Err(format!(
-                    "matched to `{matches:?}` with length {}, but expected length {expected}",
-                    matches.len(),
-                ));
-            }
-        }
-        CommandKind::Set { variable } => {
-            let value = get_one(&matches)?;
-            let r = cache.variables.insert(variable.to_owned(), value.clone());
-            assert!(r.is_none(), "name collision: {variable:?} is duplicated");
-        }
-    }
-
-    Ok(())
-}
-
-fn get_one<'a>(matches: &[&'a Value]) -> Result<&'a Value, String> {
-    match matches {
-        [] => Err("matched to no values".to_owned()),
-        [matched] => Ok(matched),
-        _ => Err(format!("matched to multiple values {matches:?}, but want exactly 1")),
-    }
-}
-
-fn string_to_value<'a>(s: &str, cache: &'a Cache) -> Cow<'a, Value> {
-    if s.starts_with("$") {
-        Cow::Borrowed(&cache.variables.get(&s[1..]).unwrap_or_else(|| {
-            // FIXME(adotinthevoid): Show line number
-            panic!("No variable: `{}`. Current state: `{:?}`", &s[1..], cache.variables)
-        }))
-    } else {
-        Cow::Owned(serde_json::from_str(s).expect(&format!("Cannot convert `{}` to json", s)))
-    }
+    if !errors { Ok(directives) } else { Err(()) }
 }
diff --git a/src/tools/miri/tests/fail/async-shared-mutable.rs b/src/tools/miri/tests/fail/async-shared-mutable.rs
new file mode 100644
index 00000000000..62780e7a11c
--- /dev/null
+++ b/src/tools/miri/tests/fail/async-shared-mutable.rs
@@ -0,0 +1,25 @@
+//! FIXME: This test should pass! However, `async fn` does not yet use `UnsafePinned`.
+//! This is a regression test for <https://github.com/rust-lang/rust/issues/137750>:
+//! `UnsafePinned` must include the effects of `UnsafeCell`.
+//@revisions: stack tree
+//@[tree]compile-flags: -Zmiri-tree-borrows
+//@normalize-stderr-test: "\[0x[a-fx\d.]+\]" -> "[OFFSET]"
+
+use core::future::Future;
+use core::pin::{Pin, pin};
+use core::task::{Context, Poll, Waker};
+
+fn main() {
+    let mut f = pin!(async move {
+        let x = &mut 0u8;
+        core::future::poll_fn(move |_| {
+            *x = 1; //~ERROR: write access
+            Poll::<()>::Pending
+        })
+        .await
+    });
+    let mut cx = Context::from_waker(&Waker::noop());
+    assert_eq!(f.as_mut().poll(&mut cx), Poll::Pending);
+    let _: Pin<&_> = f.as_ref(); // Or: `f.as_mut().into_ref()`.
+    assert_eq!(f.as_mut().poll(&mut cx), Poll::Pending);
+}
diff --git a/src/tools/miri/tests/fail/async-shared-mutable.stack.stderr b/src/tools/miri/tests/fail/async-shared-mutable.stack.stderr
new file mode 100644
index 00000000000..8f53a55cc3e
--- /dev/null
+++ b/src/tools/miri/tests/fail/async-shared-mutable.stack.stderr
@@ -0,0 +1,43 @@
+error: Undefined Behavior: attempting a write access using <TAG> at ALLOC[OFFSET], but that tag does not exist in the borrow stack for this location
+  --> tests/fail/async-shared-mutable.rs:LL:CC
+   |
+LL |             *x = 1;
+   |             ^^^^^^
+   |             |
+   |             attempting a write access using <TAG> at ALLOC[OFFSET], but that tag does not exist in the borrow stack for this location
+   |             this error occurs as part of an access at ALLOC[OFFSET]
+   |
+   = help: this indicates a potential bug in the program: it performed an invalid operation, but the Stacked Borrows rules it violated are still experimental
+   = help: see https://github.com/rust-lang/unsafe-code-guidelines/blob/master/wip/stacked-borrows.md for further information
+help: <TAG> was created by a Unique retag at offsets [OFFSET]
+  --> tests/fail/async-shared-mutable.rs:LL:CC
+   |
+LL | /         core::future::poll_fn(move |_| {
+LL | |             *x = 1;
+LL | |             Poll::<()>::Pending
+LL | |         })
+LL | |         .await
+   | |______________^
+help: <TAG> was later invalidated at offsets [OFFSET] by a SharedReadOnly retag
+  --> tests/fail/async-shared-mutable.rs:LL:CC
+   |
+LL |     let _: Pin<&_> = f.as_ref(); // Or: `f.as_mut().into_ref()`.
+   |                      ^^^^^^^^^^
+   = note: BACKTRACE (of the first span):
+   = note: inside closure at tests/fail/async-shared-mutable.rs:LL:CC
+   = note: inside `<std::future::PollFn<{closure@tests/fail/async-shared-mutable.rs:LL:CC}> as std::future::Future>::poll` at RUSTLIB/core/src/future/poll_fn.rs:LL:CC
+note: inside closure
+  --> tests/fail/async-shared-mutable.rs:LL:CC
+   |
+LL |         .await
+   |          ^^^^^
+note: inside `main`
+  --> tests/fail/async-shared-mutable.rs:LL:CC
+   |
+LL |     assert_eq!(f.as_mut().poll(&mut cx), Poll::Pending);
+   |                ^^^^^^^^^^^^^^^^^^^^^^^^
+
+note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
+
+error: aborting due to 1 previous error
+
diff --git a/src/tools/miri/tests/fail/async-shared-mutable.tree.stderr b/src/tools/miri/tests/fail/async-shared-mutable.tree.stderr
new file mode 100644
index 00000000000..d1e66a0d043
--- /dev/null
+++ b/src/tools/miri/tests/fail/async-shared-mutable.tree.stderr
@@ -0,0 +1,47 @@
+error: Undefined Behavior: write access through <TAG> at ALLOC[OFFSET] is forbidden
+  --> tests/fail/async-shared-mutable.rs:LL:CC
+   |
+LL |             *x = 1;
+   |             ^^^^^^ write access through <TAG> at ALLOC[OFFSET] is forbidden
+   |
+   = help: this indicates a potential bug in the program: it performed an invalid operation, but the Tree Borrows rules it violated are still experimental
+   = help: the accessed tag <TAG> has state Frozen which forbids this child write access
+help: the accessed tag <TAG> was created here, in the initial state Reserved
+  --> tests/fail/async-shared-mutable.rs:LL:CC
+   |
+LL | /         core::future::poll_fn(move |_| {
+LL | |             *x = 1;
+LL | |             Poll::<()>::Pending
+LL | |         })
+LL | |         .await
+   | |______________^
+help: the accessed tag <TAG> later transitioned to Active due to a child write access at offsets [OFFSET]
+  --> tests/fail/async-shared-mutable.rs:LL:CC
+   |
+LL |             *x = 1;
+   |             ^^^^^^
+   = help: this transition corresponds to the first write to a 2-phase borrowed mutable reference
+help: the accessed tag <TAG> later transitioned to Frozen due to a reborrow (acting as a foreign read access) at offsets [OFFSET]
+  --> tests/fail/async-shared-mutable.rs:LL:CC
+   |
+LL |     let _: Pin<&_> = f.as_ref(); // Or: `f.as_mut().into_ref()`.
+   |                      ^^^^^^^^^^
+   = help: this transition corresponds to a loss of write permissions
+   = note: BACKTRACE (of the first span):
+   = note: inside closure at tests/fail/async-shared-mutable.rs:LL:CC
+   = note: inside `<std::future::PollFn<{closure@tests/fail/async-shared-mutable.rs:LL:CC}> as std::future::Future>::poll` at RUSTLIB/core/src/future/poll_fn.rs:LL:CC
+note: inside closure
+  --> tests/fail/async-shared-mutable.rs:LL:CC
+   |
+LL |         .await
+   |          ^^^^^
+note: inside `main`
+  --> tests/fail/async-shared-mutable.rs:LL:CC
+   |
+LL |     assert_eq!(f.as_mut().poll(&mut cx), Poll::Pending);
+   |                ^^^^^^^^^^^^^^^^^^^^^^^^
+
+note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
+
+error: aborting due to 1 previous error
+
diff --git a/src/tools/miri/tests/pass/both_borrows/unsafe_pinned.rs b/src/tools/miri/tests/pass/both_borrows/unsafe_pinned.rs
new file mode 100644
index 00000000000..0c75a07bfa2
--- /dev/null
+++ b/src/tools/miri/tests/pass/both_borrows/unsafe_pinned.rs
@@ -0,0 +1,16 @@
+//@revisions: stack tree
+//@[tree]compile-flags: -Zmiri-tree-borrows
+#![feature(unsafe_pinned)]
+
+use std::pin::UnsafePinned;
+
+fn mutate(x: &UnsafePinned<i32>) {
+    let ptr = x as *const _ as *mut i32;
+    unsafe { ptr.write(42) };
+}
+
+fn main() {
+    let x = UnsafePinned::new(0);
+    mutate(&x);
+    assert_eq!(x.into_inner(), 42);
+}
diff --git a/src/tools/miri/tests/pass/fat_ptr.rs b/src/tools/miri/tests/pass/fat_ptr.rs
index c5603d2cf80..13608b8f898 100644
--- a/src/tools/miri/tests/pass/fat_ptr.rs
+++ b/src/tools/miri/tests/pass/fat_ptr.rs
@@ -19,11 +19,11 @@ fn fat_ptr_via_local(a: &[u8]) -> &[u8] {
     x
 }
 
-fn fat_ptr_from_struct(s: FatPtrContainer) -> &[u8] {
+fn fat_ptr_from_struct(s: FatPtrContainer<'_>) -> &[u8] {
     s.ptr
 }
 
-fn fat_ptr_to_struct(a: &[u8]) -> FatPtrContainer {
+fn fat_ptr_to_struct(a: &[u8]) -> FatPtrContainer<'_> {
     FatPtrContainer { ptr: a }
 }