Auto merge of #96891 - Dylan-DPC:rollup-echa4wg, r=Dylan-DPC

Rollup of 5 pull requests

Successful merges:

 - #93661 (Add missing rustc arg docs)
 - #96674 (docs: add link explaining variance to NonNull docs)
 - #96812 (Do not lint on explicit outlives requirements from external macros.)
 - #96823 (Properly fix #96638)
 - #96872 (make sure ScalarPair enums have ScalarPair variants; add some layout sanity checks)

Failed merges:

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

9 files changed, 202 insertions, 22 deletions

diff --git a/src/doc/rustc/src/codegen-options/index.md b/src/doc/rustc/src/codegen-options/index.md
index 3b0cf92bbb7..02011325d68 100644
--- a/src/doc/rustc/src/codegen-options/index.md
+++ b/src/doc/rustc/src/codegen-options/index.md
@@ -550,6 +550,21 @@ Supported values for this option are:
 - `symbols` - same as `debuginfo`, but the rest of the symbol table section is
   stripped as well if the linker supports it.
 
+## symbol-mangling-version
+
+This option controls the [name mangling] format for encoding Rust item names
+for the purpose of generating object code and linking.
+
+Supported values for this option are:
+
+* `v0` — The "v0" mangling scheme. The specific format is not specified at
+  this time.
+
+The default if not specified will use a compiler-chosen default which may
+change in the future.
+
+[name mangling]: https://en.wikipedia.org/wiki/Name_mangling
+
 ## target-cpu
 
 This instructs `rustc` to generate code specifically for a particular processor.
diff --git a/src/doc/rustc/src/command-line-arguments.md b/src/doc/rustc/src/command-line-arguments.md
index bee9a8d808f..0d02fa7bd6b 100644
--- a/src/doc/rustc/src/command-line-arguments.md
+++ b/src/doc/rustc/src/command-line-arguments.md
@@ -408,6 +408,9 @@ to customize the output:
   argument](#option-emit), and as soon as the artifact is available on the
   filesystem a notification will be emitted.
 
+- `future-incompat` - includes a JSON message that contains a report if the
+  crate contains any code that may fail to compile in the future.
+
 Note that it is invalid to combine the `--json` argument with the
 [`--color`](#option-color) argument, and it is required to combine `--json`
 with `--error-format=json`.
diff --git a/src/doc/rustc/src/json.md b/src/doc/rustc/src/json.md
index 5dee603142d..efbf861eaa6 100644
--- a/src/doc/rustc/src/json.md
+++ b/src/doc/rustc/src/json.md
@@ -229,6 +229,32 @@ flag][option-emit] documentation.
 }
 ```
 
+## Future-incompatible reports
+
+If the [`--json=future-incompat`][option-json] flag is used, then a separate
+JSON structure will be emitted if the crate may stop compiling in the future.
+This contains diagnostic information about the particular warnings that may be
+turned into a hard error in the future. This will include the diagnostic
+information, even if the diagnostics have been suppressed (such as with an
+`#[allow]` attribute or the `--cap-lints` option).
+
+```javascript
+{
+    /* An array of objects describing a warning that will become a hard error
+       in the future.
+    */
+    "future_incompat_report":
+    [
+        {
+            /* A diagnostic structure as defined in
+               https://doc.rust-lang.org/rustc/json.html#diagnostics
+            */
+            "diagnostic": {...},
+        }
+    ]
+}
+```
+
 [option-emit]: command-line-arguments.md#option-emit
 [option-error-format]: command-line-arguments.md#option-error-format
 [option-json]: command-line-arguments.md#option-json
diff --git a/src/test/codegen/align-struct.rs b/src/test/codegen/align-struct.rs
index acc5a2d5499..f129f073e98 100644
--- a/src/test/codegen/align-struct.rs
+++ b/src/test/codegen/align-struct.rs
@@ -19,7 +19,7 @@ pub enum Enum4 {
     A(i32),
     B(i32),
 }
-// CHECK: %"Enum4::A" = type { [1 x i32], i32 }
+// No Aggregate type, and hence nothing in LLVM IR.
 
 pub enum Enum64 {
     A(Align64),
diff --git a/src/test/ui/layout/debug.stderr b/src/test/ui/layout/debug.stderr
index 56a1337e6a5..7dbcc151855 100644
--- a/src/test/ui/layout/debug.stderr
+++ b/src/test/ui/layout/debug.stderr
@@ -184,9 +184,22 @@ error: layout_of(std::result::Result<i32, i32>) = Layout {
                        variants: Single {
                            index: 0,
                        },
-                       abi: Aggregate {
-                           sized: true,
-                       },
+                       abi: ScalarPair(
+                           Initialized {
+                               value: Int(
+                                   I32,
+                                   false,
+                               ),
+                               valid_range: 0..=1,
+                           },
+                           Initialized {
+                               value: Int(
+                                   I32,
+                                   true,
+                               ),
+                               valid_range: 0..=4294967295,
+                           },
+                       ),
                        largest_niche: None,
                        align: AbiAndPrefAlign {
                            abi: Align(4 bytes),
@@ -206,9 +219,22 @@ error: layout_of(std::result::Result<i32, i32>) = Layout {
                        variants: Single {
                            index: 1,
                        },
-                       abi: Aggregate {
-                           sized: true,
-                       },
+                       abi: ScalarPair(
+                           Initialized {
+                               value: Int(
+                                   I32,
+                                   false,
+                               ),
+                               valid_range: 0..=1,
+                           },
+                           Initialized {
+                               value: Int(
+                                   I32,
+                                   true,
+                               ),
+                               valid_range: 0..=4294967295,
+                           },
+                       ),
                        largest_niche: None,
                        align: AbiAndPrefAlign {
                            abi: Align(4 bytes),
diff --git a/src/test/ui/layout/issue-96158-scalarpair-payload-might-be-uninit.stderr b/src/test/ui/layout/issue-96158-scalarpair-payload-might-be-uninit.stderr
index 1a724e6f59b..33dfa307c1d 100644
--- a/src/test/ui/layout/issue-96158-scalarpair-payload-might-be-uninit.stderr
+++ b/src/test/ui/layout/issue-96158-scalarpair-payload-might-be-uninit.stderr
@@ -30,9 +30,21 @@ error: layout_of(MissingPayloadField) = Layout {
                        variants: Single {
                            index: 0,
                        },
-                       abi: Aggregate {
-                           sized: true,
-                       },
+                       abi: ScalarPair(
+                           Initialized {
+                               value: Int(
+                                   I8,
+                                   false,
+                               ),
+                               valid_range: 0..=1,
+                           },
+                           Union {
+                               value: Int(
+                                   I8,
+                                   false,
+                               ),
+                           },
+                       ),
                        largest_niche: None,
                        align: AbiAndPrefAlign {
                            abi: Align(1 bytes),
@@ -131,9 +143,22 @@ error: layout_of(CommonPayloadField) = Layout {
                        variants: Single {
                            index: 0,
                        },
-                       abi: Aggregate {
-                           sized: true,
-                       },
+                       abi: ScalarPair(
+                           Initialized {
+                               value: Int(
+                                   I8,
+                                   false,
+                               ),
+                               valid_range: 0..=1,
+                           },
+                           Initialized {
+                               value: Int(
+                                   I8,
+                                   false,
+                               ),
+                               valid_range: 0..=255,
+                           },
+                       ),
                        largest_niche: None,
                        align: AbiAndPrefAlign {
                            abi: Align(1 bytes),
@@ -153,9 +178,22 @@ error: layout_of(CommonPayloadField) = Layout {
                        variants: Single {
                            index: 1,
                        },
-                       abi: Aggregate {
-                           sized: true,
-                       },
+                       abi: ScalarPair(
+                           Initialized {
+                               value: Int(
+                                   I8,
+                                   false,
+                               ),
+                               valid_range: 0..=1,
+                           },
+                           Initialized {
+                               value: Int(
+                                   I8,
+                                   false,
+                               ),
+                               valid_range: 0..=255,
+                           },
+                       ),
                        largest_niche: None,
                        align: AbiAndPrefAlign {
                            abi: Align(1 bytes),
@@ -237,9 +275,21 @@ error: layout_of(CommonPayloadFieldIsMaybeUninit) = Layout {
                        variants: Single {
                            index: 0,
                        },
-                       abi: Aggregate {
-                           sized: true,
-                       },
+                       abi: ScalarPair(
+                           Initialized {
+                               value: Int(
+                                   I8,
+                                   false,
+                               ),
+                               valid_range: 0..=1,
+                           },
+                           Union {
+                               value: Int(
+                                   I8,
+                                   false,
+                               ),
+                           },
+                       ),
                        largest_niche: None,
                        align: AbiAndPrefAlign {
                            abi: Align(1 bytes),
@@ -259,9 +309,21 @@ error: layout_of(CommonPayloadFieldIsMaybeUninit) = Layout {
                        variants: Single {
                            index: 1,
                        },
-                       abi: Aggregate {
-                           sized: true,
-                       },
+                       abi: ScalarPair(
+                           Initialized {
+                               value: Int(
+                                   I8,
+                                   false,
+                               ),
+                               valid_range: 0..=1,
+                           },
+                           Union {
+                               value: Int(
+                                   I8,
+                                   false,
+                               ),
+                           },
+                       ),
                        largest_niche: None,
                        align: AbiAndPrefAlign {
                            abi: Align(1 bytes),
diff --git a/src/test/ui/rust-2018/auxiliary/edition-lint-infer-outlives-macro.rs b/src/test/ui/rust-2018/auxiliary/edition-lint-infer-outlives-macro.rs
new file mode 100644
index 00000000000..d45fa10f022
--- /dev/null
+++ b/src/test/ui/rust-2018/auxiliary/edition-lint-infer-outlives-macro.rs
@@ -0,0 +1,6 @@
+pub fn foo() {}
+
+#[macro_export]
+macro_rules! gimme_a {
+    ($($mac:tt)*) => { $($mac)* { 'a } }
+}
diff --git a/src/test/ui/rust-2018/edition-lint-infer-outlives-macro.rs b/src/test/ui/rust-2018/edition-lint-infer-outlives-macro.rs
new file mode 100644
index 00000000000..d7a832831c1
--- /dev/null
+++ b/src/test/ui/rust-2018/edition-lint-infer-outlives-macro.rs
@@ -0,0 +1,28 @@
+// edition:2018
+// aux-build:edition-lint-infer-outlives-macro.rs
+
+// Test that the lint does not fire if the where predicate
+// is from the local crate, but all the bounds are from an
+// external macro.
+
+#![deny(explicit_outlives_requirements)]
+
+#[macro_use]
+extern crate edition_lint_infer_outlives_macro;
+
+macro_rules! make_foo {
+    ($a:tt) => {
+        struct Foo<$a, 'b> where 'b: $a {
+            foo: &$a &'b (),
+        }
+    }
+}
+
+gimme_a! {make_foo!}
+
+struct Bar<'a, 'b: 'a> {
+    //~^ ERROR: outlives requirements can be inferred
+    bar: &'a &'b (),
+}
+
+fn main() {}
diff --git a/src/test/ui/rust-2018/edition-lint-infer-outlives-macro.stderr b/src/test/ui/rust-2018/edition-lint-infer-outlives-macro.stderr
new file mode 100644
index 00000000000..553b1cd976a
--- /dev/null
+++ b/src/test/ui/rust-2018/edition-lint-infer-outlives-macro.stderr
@@ -0,0 +1,14 @@
+error: outlives requirements can be inferred
+  --> $DIR/edition-lint-infer-outlives-macro.rs:23:18
+   |
+LL | struct Bar<'a, 'b: 'a> {
+   |                  ^^^^ help: remove this bound
+   |
+note: the lint level is defined here
+  --> $DIR/edition-lint-infer-outlives-macro.rs:8:9
+   |
+LL | #![deny(explicit_outlives_requirements)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to previous error
+