Rollup merge of #63492 - eddyb:cvarargs, r=nagisa,matthewjasper

Remove redundancy from the implementation of C variadics.

This cleanup was first described in https://github.com/rust-lang/rust/issues/44930#issuecomment-497163539:

* AST doesn't track `c_variadic: bool` anymore, relying solely on a trailing `CVarArgs` type in fn signatures
* HIR doesn't have a `CVarArgs` anymore, relying solely on `c_variadic: bool`
  * same for `ty::FnSig` (see tests for diagnostics improvements from that)
  * `{hir,mir}::Body` have one extra argument than the signature when `c_variadic == true`
  * `rustc_typeck` and `rustc_mir::{build,borrowck}` need to give that argument the right type (which no longer uses a lifetime parameter, but a function-internal scope)
* `rustc_target::abi::call` doesn't need special hacks anymore (since it never sees the `VaListImpl` now, it's all inside the body)

r? @nagisa / @rkruppe cc @dlrobertson @oli-obk

11 files changed, 138 insertions, 197 deletions

diff --git a/src/test/rustdoc/variadic.rs b/src/test/rustdoc/variadic.rs
index 5af2aea21fc..bd8f1775b3d 100644
--- a/src/test/rustdoc/variadic.rs
+++ b/src/test/rustdoc/variadic.rs
@@ -1,4 +1,4 @@
 extern "C" {
-    // @has variadic/fn.foo.html //pre 'pub unsafe extern "C" fn foo(x: i32, _: ...)'
+    // @has variadic/fn.foo.html //pre 'pub unsafe extern "C" fn foo(x: i32, ...)'
     pub fn foo(x: i32, ...);
 }
diff --git a/src/test/ui-fulldeps/pprust-expr-roundtrip.rs b/src/test/ui-fulldeps/pprust-expr-roundtrip.rs
index 784f71a61fd..d4aff735907 100644
--- a/src/test/ui-fulldeps/pprust-expr-roundtrip.rs
+++ b/src/test/ui-fulldeps/pprust-expr-roundtrip.rs
@@ -114,7 +114,6 @@ fn iter_exprs(depth: usize, f: &mut dyn FnMut(P<Expr>)) {
                 let decl = P(FnDecl {
                     inputs: vec![],
                     output: FunctionRetTy::Default(DUMMY_SP),
-                    c_variadic: false,
                 });
                 iter_exprs(depth - 1, &mut |e| g(
                         ExprKind::Closure(CaptureBy::Value,
diff --git a/src/test/ui/c-variadic/variadic-ffi-1.stderr b/src/test/ui/c-variadic/variadic-ffi-1.stderr
index 695eba2a7ee..73f72a177bc 100644
--- a/src/test/ui/c-variadic/variadic-ffi-1.stderr
+++ b/src/test/ui/c-variadic/variadic-ffi-1.stderr
@@ -29,7 +29,7 @@ LL |         let x: unsafe extern "C" fn(f: isize, x: u8) = foo;
    |                                                        ^^^ expected non-variadic fn, found variadic function
    |
    = note: expected type `unsafe extern "C" fn(isize, u8)`
-              found type `for<'r> unsafe extern "C" fn(isize, u8, std::ffi::VaListImpl<'r>, ...) {foo}`
+              found type `unsafe extern "C" fn(isize, u8, ...) {foo}`
 
 error[E0308]: mismatched types
   --> $DIR/variadic-ffi-1.rs:20:54
@@ -37,7 +37,7 @@ error[E0308]: mismatched types
 LL |         let y: extern "C" fn(f: isize, x: u8, ...) = bar;
    |                                                      ^^^ expected variadic fn, found non-variadic function
    |
-   = note: expected type `for<'r> extern "C" fn(isize, u8, std::ffi::VaListImpl<'r>, ...)`
+   = note: expected type `extern "C" fn(isize, u8, ...)`
               found type `extern "C" fn(isize, u8) {bar}`
 
 error[E0617]: can't pass `f32` to variadic function
diff --git a/src/test/ui/c-variadic/variadic-ffi-4.nll.stderr b/src/test/ui/c-variadic/variadic-ffi-4.nll.stderr
index ab8398ec5e9..8b70b15fa6e 100644
--- a/src/test/ui/c-variadic/variadic-ffi-4.nll.stderr
+++ b/src/test/ui/c-variadic/variadic-ffi-4.nll.stderr
@@ -1,18 +1,30 @@
-error[E0621]: explicit lifetime required in the type of `ap`
+error: lifetime may not live long enough
+  --> $DIR/variadic-ffi-4.rs:8:5
+   |
+LL | pub unsafe extern "C" fn no_escape0<'f>(_: usize, ap: ...) -> VaListImpl<'f> {
+   |                                     --            -- has type `core::ffi::VaListImpl<'1>`
+   |                                     |
+   |                                     lifetime `'f` defined here
+LL |     ap
+   |     ^^ function was supposed to return data with lifetime `'1` but it is returning data with lifetime `'f`
+
+error: lifetime may not live long enough
   --> $DIR/variadic-ffi-4.rs:8:5
    |
 LL | pub unsafe extern "C" fn no_escape0<'f>(_: usize, ap: ...) -> VaListImpl<'f> {
-   |                                                       --- help: add explicit lifetime `'f` to the type of `ap`: `core::ffi::VaListImpl<'f>`
+   |                                     --            -- has type `core::ffi::VaListImpl<'1>`
+   |                                     |
+   |                                     lifetime `'f` defined here
 LL |     ap
-   |     ^^ lifetime `'f` required
+   |     ^^ returning this value requires that `'1` must outlive `'f`
 
-error[E0621]: explicit lifetime required in the type of `ap`
+error: lifetime may not live long enough
   --> $DIR/variadic-ffi-4.rs:12:5
    |
 LL | pub unsafe extern "C" fn no_escape1(_: usize, ap: ...) -> VaListImpl<'static> {
-   |                                                   --- help: add explicit lifetime `'static` to the type of `ap`: `core::ffi::VaListImpl<'static>`
+   |                                               -- has type `core::ffi::VaListImpl<'1>`
 LL |     ap
-   |     ^^ lifetime `'static` required
+   |     ^^ returning this value requires that `'1` must outlive `'static`
 
 error: lifetime may not live long enough
   --> $DIR/variadic-ffi-4.rs:16:33
@@ -44,7 +56,7 @@ LL |     *ap0 = ap1;
    |     ^^^^ assignment requires that `'2` must outlive `'1`
 
 error: lifetime may not live long enough
-  --> $DIR/variadic-ffi-4.rs:25:5
+  --> $DIR/variadic-ffi-4.rs:24:5
    |
 LL | pub unsafe extern "C" fn no_escape4(_: usize, ap0: &mut VaListImpl, mut ap1: ...) {
    |                                               ---                   ------- has type `core::ffi::VaListImpl<'2>`
@@ -54,7 +66,7 @@ LL |     ap0 = &mut ap1;
    |     ^^^^^^^^^^^^^^ assignment requires that `'1` must outlive `'2`
 
 error: lifetime may not live long enough
-  --> $DIR/variadic-ffi-4.rs:25:5
+  --> $DIR/variadic-ffi-4.rs:24:5
    |
 LL | pub unsafe extern "C" fn no_escape4(_: usize, ap0: &mut VaListImpl, mut ap1: ...) {
    |                                               ---                   ------- has type `core::ffi::VaListImpl<'2>`
@@ -64,7 +76,7 @@ LL |     ap0 = &mut ap1;
    |     ^^^^^^^^^^^^^^ assignment requires that `'2` must outlive `'1`
 
 error[E0384]: cannot assign to immutable argument `ap0`
-  --> $DIR/variadic-ffi-4.rs:25:5
+  --> $DIR/variadic-ffi-4.rs:24:5
    |
 LL | pub unsafe extern "C" fn no_escape4(_: usize, ap0: &mut VaListImpl, mut ap1: ...) {
    |                                               --- help: make this binding mutable: `mut ap0`
@@ -72,7 +84,7 @@ LL |     ap0 = &mut ap1;
    |     ^^^^^^^^^^^^^^ cannot assign to immutable argument
 
 error[E0597]: `ap1` does not live long enough
-  --> $DIR/variadic-ffi-4.rs:25:11
+  --> $DIR/variadic-ffi-4.rs:24:11
    |
 LL | pub unsafe extern "C" fn no_escape4(_: usize, ap0: &mut VaListImpl, mut ap1: ...) {
    |                                                    - let's call the lifetime of this reference `'1`
@@ -86,7 +98,7 @@ LL | }
    | - `ap1` dropped here while still borrowed
 
 error: lifetime may not live long enough
-  --> $DIR/variadic-ffi-4.rs:33:12
+  --> $DIR/variadic-ffi-4.rs:31:12
    |
 LL | pub unsafe extern "C" fn no_escape5(_: usize, mut ap0: &mut VaListImpl, mut ap1: ...) {
    |                                               -------                   ------- has type `core::ffi::VaListImpl<'2>`
@@ -96,7 +108,7 @@ LL |     *ap0 = ap1.clone();
    |            ^^^^^^^^^^^ argument requires that `'1` must outlive `'2`
 
 error: lifetime may not live long enough
-  --> $DIR/variadic-ffi-4.rs:33:12
+  --> $DIR/variadic-ffi-4.rs:31:12
    |
 LL | pub unsafe extern "C" fn no_escape5(_: usize, mut ap0: &mut VaListImpl, mut ap1: ...) {
    |                                               -------                   ------- has type `core::ffi::VaListImpl<'2>`
@@ -105,7 +117,7 @@ LL | pub unsafe extern "C" fn no_escape5(_: usize, mut ap0: &mut VaListImpl, mut
 LL |     *ap0 = ap1.clone();
    |            ^^^^^^^^^^^ argument requires that `'2` must outlive `'1`
 
-error: aborting due to 11 previous errors
+error: aborting due to 12 previous errors
 
-Some errors have detailed explanations: E0384, E0597, E0621.
+Some errors have detailed explanations: E0384, E0597.
 For more information about an error, try `rustc --explain E0384`.
diff --git a/src/test/ui/c-variadic/variadic-ffi-4.rs b/src/test/ui/c-variadic/variadic-ffi-4.rs
index 4a50d352a5b..a4d658cef16 100644
--- a/src/test/ui/c-variadic/variadic-ffi-4.rs
+++ b/src/test/ui/c-variadic/variadic-ffi-4.rs
@@ -5,11 +5,11 @@
 use core::ffi::{VaList, VaListImpl};
 
 pub unsafe extern "C" fn no_escape0<'f>(_: usize, ap: ...) -> VaListImpl<'f> {
-    ap //~ ERROR: explicit lifetime required
+    ap //~ ERROR: mismatched types
 }
 
 pub unsafe extern "C" fn no_escape1(_: usize, ap: ...) -> VaListImpl<'static> {
-    ap //~ ERROR: explicit lifetime required
+    ap //~ ERROR: mismatched types
 }
 
 pub unsafe extern "C" fn no_escape2(_: usize, ap: ...) {
@@ -18,18 +18,15 @@ pub unsafe extern "C" fn no_escape2(_: usize, ap: ...) {
 
 pub unsafe extern "C" fn no_escape3(_: usize, mut ap0: &mut VaListImpl, mut ap1: ...) {
     *ap0 = ap1; //~ ERROR: mismatched types
-    //~^ ERROR: mismatched types
 }
 
 pub unsafe extern "C" fn no_escape4(_: usize, ap0: &mut VaListImpl, mut ap1: ...) {
     ap0 = &mut ap1;
     //~^ ERROR: a value of type `core::ffi::VaListImpl<'_>` is borrowed for too long
-    //~^^ ERROR: mismatched types
-    //~^^^ ERROR: mismatched types
-    //~^^^^ ERROR: cannot infer an appropriate lifetime
+    //~| ERROR: mismatched types
+    //~| ERROR: cannot infer an appropriate lifetime
 }
 
 pub unsafe extern "C" fn no_escape5(_: usize, mut ap0: &mut VaListImpl, mut ap1: ...) {
     *ap0 = ap1.clone(); //~ ERROR: mismatched types
-    //~^ ERROR: mismatched types
 }
diff --git a/src/test/ui/c-variadic/variadic-ffi-4.stderr b/src/test/ui/c-variadic/variadic-ffi-4.stderr
index 7aa510e6113..b986d0c2435 100644
--- a/src/test/ui/c-variadic/variadic-ffi-4.stderr
+++ b/src/test/ui/c-variadic/variadic-ffi-4.stderr
@@ -1,18 +1,42 @@
-error[E0621]: explicit lifetime required in the type of `ap`
+error[E0308]: mismatched types
   --> $DIR/variadic-ffi-4.rs:8:5
    |
-LL | pub unsafe extern "C" fn no_escape0<'f>(_: usize, ap: ...) -> VaListImpl<'f> {
-   |                                                       --- help: add explicit lifetime `'f` to the type of `ap`: `core::ffi::VaListImpl<'f>`
 LL |     ap
-   |     ^^ lifetime `'f` required
+   |     ^^ lifetime mismatch
+   |
+   = note: expected type `core::ffi::VaListImpl<'f>`
+              found type `core::ffi::VaListImpl<'_>`
+note: the scope of call-site for function at 7:78...
+  --> $DIR/variadic-ffi-4.rs:7:78
+   |
+LL |   pub unsafe extern "C" fn no_escape0<'f>(_: usize, ap: ...) -> VaListImpl<'f> {
+   |  ______________________________________________________________________________^
+LL | |     ap
+LL | | }
+   | |_^
+note: ...does not necessarily outlive the lifetime 'f as defined on the function body at 7:37
+  --> $DIR/variadic-ffi-4.rs:7:37
+   |
+LL | pub unsafe extern "C" fn no_escape0<'f>(_: usize, ap: ...) -> VaListImpl<'f> {
+   |                                     ^^
 
-error[E0621]: explicit lifetime required in the type of `ap`
+error[E0308]: mismatched types
   --> $DIR/variadic-ffi-4.rs:12:5
    |
-LL | pub unsafe extern "C" fn no_escape1(_: usize, ap: ...) -> VaListImpl<'static> {
-   |                                                   --- help: add explicit lifetime `'static` to the type of `ap`: `core::ffi::VaListImpl<'static>`
 LL |     ap
-   |     ^^ lifetime `'static` required
+   |     ^^ lifetime mismatch
+   |
+   = note: expected type `core::ffi::VaListImpl<'static>`
+              found type `core::ffi::VaListImpl<'_>`
+note: the scope of call-site for function at 11:79...
+  --> $DIR/variadic-ffi-4.rs:11:79
+   |
+LL |   pub unsafe extern "C" fn no_escape1(_: usize, ap: ...) -> VaListImpl<'static> {
+   |  _______________________________________________________________________________^
+LL | |     ap
+LL | | }
+   | |_^
+   = note: ...does not necessarily outlive the static lifetime
 
 error[E0495]: cannot infer an appropriate lifetime due to conflicting requirements
   --> $DIR/variadic-ffi-4.rs:16:33
@@ -47,12 +71,12 @@ LL |     *ap0 = ap1;
    |
    = note: expected type `core::ffi::VaListImpl<'_>`
               found type `core::ffi::VaListImpl<'_>`
-note: the anonymous lifetime #3 defined on the function body at 19:1...
-  --> $DIR/variadic-ffi-4.rs:19:1
+note: the scope of call-site for function at 19:87...
+  --> $DIR/variadic-ffi-4.rs:19:87
    |
-LL | / pub unsafe extern "C" fn no_escape3(_: usize, mut ap0: &mut VaListImpl, mut ap1: ...) {
+LL |   pub unsafe extern "C" fn no_escape3(_: usize, mut ap0: &mut VaListImpl, mut ap1: ...) {
+   |  _______________________________________________________________________________________^
 LL | |     *ap0 = ap1;
-LL | |
 LL | | }
    | |_^
 note: ...does not necessarily outlive the anonymous lifetime #2 defined on the function body at 19:1
@@ -60,216 +84,129 @@ note: ...does not necessarily outlive the anonymous lifetime #2 defined on the f
    |
 LL | / pub unsafe extern "C" fn no_escape3(_: usize, mut ap0: &mut VaListImpl, mut ap1: ...) {
 LL | |     *ap0 = ap1;
-LL | |
-LL | | }
-   | |_^
-
-error[E0308]: mismatched types
-  --> $DIR/variadic-ffi-4.rs:20:12
-   |
-LL |     *ap0 = ap1;
-   |            ^^^ lifetime mismatch
-   |
-   = note: expected type `core::ffi::VaListImpl<'_>`
-              found type `core::ffi::VaListImpl<'_>`
-note: the anonymous lifetime #2 defined on the function body at 19:1...
-  --> $DIR/variadic-ffi-4.rs:19:1
-   |
-LL | / pub unsafe extern "C" fn no_escape3(_: usize, mut ap0: &mut VaListImpl, mut ap1: ...) {
-LL | |     *ap0 = ap1;
-LL | |
-LL | | }
-   | |_^
-note: ...does not necessarily outlive the anonymous lifetime #3 defined on the function body at 19:1
-  --> $DIR/variadic-ffi-4.rs:19:1
-   |
-LL | / pub unsafe extern "C" fn no_escape3(_: usize, mut ap0: &mut VaListImpl, mut ap1: ...) {
-LL | |     *ap0 = ap1;
-LL | |
 LL | | }
    | |_^
 
 error[E0490]: a value of type `core::ffi::VaListImpl<'_>` is borrowed for too long
-  --> $DIR/variadic-ffi-4.rs:25:11
+  --> $DIR/variadic-ffi-4.rs:24:11
    |
 LL |     ap0 = &mut ap1;
    |           ^^^^^^^^
    |
-note: the type is valid for the anonymous lifetime #1 defined on the function body at 24:1
-  --> $DIR/variadic-ffi-4.rs:24:1
-   |
-LL | / pub unsafe extern "C" fn no_escape4(_: usize, ap0: &mut VaListImpl, mut ap1: ...) {
-LL | |     ap0 = &mut ap1;
-LL | |
-LL | |
-LL | |
-LL | |
-LL | | }
-   | |_^
-note: but the borrow lasts for the anonymous lifetime #3 defined on the function body at 24:1
-  --> $DIR/variadic-ffi-4.rs:24:1
-   |
-LL | / pub unsafe extern "C" fn no_escape4(_: usize, ap0: &mut VaListImpl, mut ap1: ...) {
-LL | |     ap0 = &mut ap1;
-LL | |
-LL | |
-LL | |
-LL | |
-LL | | }
-   | |_^
-
-error[E0308]: mismatched types
-  --> $DIR/variadic-ffi-4.rs:25:11
-   |
-LL |     ap0 = &mut ap1;
-   |           ^^^^^^^^ lifetime mismatch
-   |
-   = note: expected type `&mut core::ffi::VaListImpl<'_>`
-              found type `&mut core::ffi::VaListImpl<'_>`
-note: the anonymous lifetime #3 defined on the function body at 24:1...
-  --> $DIR/variadic-ffi-4.rs:24:1
+note: the type is valid for the anonymous lifetime #1 defined on the function body at 23:1
+  --> $DIR/variadic-ffi-4.rs:23:1
    |
 LL | / pub unsafe extern "C" fn no_escape4(_: usize, ap0: &mut VaListImpl, mut ap1: ...) {
 LL | |     ap0 = &mut ap1;
 LL | |
 LL | |
 LL | |
-LL | |
 LL | | }
    | |_^
-note: ...does not necessarily outlive the anonymous lifetime #2 defined on the function body at 24:1
-  --> $DIR/variadic-ffi-4.rs:24:1
+note: but the borrow lasts for the scope of call-site for function at 23:83
+  --> $DIR/variadic-ffi-4.rs:23:83
    |
-LL | / pub unsafe extern "C" fn no_escape4(_: usize, ap0: &mut VaListImpl, mut ap1: ...) {
+LL |   pub unsafe extern "C" fn no_escape4(_: usize, ap0: &mut VaListImpl, mut ap1: ...) {
+   |  ___________________________________________________________________________________^
 LL | |     ap0 = &mut ap1;
 LL | |
 LL | |
 LL | |
-LL | |
 LL | | }
    | |_^
 
 error[E0308]: mismatched types
-  --> $DIR/variadic-ffi-4.rs:25:11
+  --> $DIR/variadic-ffi-4.rs:24:11
    |
 LL |     ap0 = &mut ap1;
    |           ^^^^^^^^ lifetime mismatch
    |
    = note: expected type `&mut core::ffi::VaListImpl<'_>`
               found type `&mut core::ffi::VaListImpl<'_>`
-note: the anonymous lifetime #2 defined on the function body at 24:1...
-  --> $DIR/variadic-ffi-4.rs:24:1
+note: the scope of call-site for function at 23:83...
+  --> $DIR/variadic-ffi-4.rs:23:83
    |
-LL | / pub unsafe extern "C" fn no_escape4(_: usize, ap0: &mut VaListImpl, mut ap1: ...) {
+LL |   pub unsafe extern "C" fn no_escape4(_: usize, ap0: &mut VaListImpl, mut ap1: ...) {
+   |  ___________________________________________________________________________________^
 LL | |     ap0 = &mut ap1;
 LL | |
 LL | |
 LL | |
-LL | |
 LL | | }
    | |_^
-note: ...does not necessarily outlive the anonymous lifetime #3 defined on the function body at 24:1
-  --> $DIR/variadic-ffi-4.rs:24:1
+note: ...does not necessarily outlive the anonymous lifetime #2 defined on the function body at 23:1
+  --> $DIR/variadic-ffi-4.rs:23:1
    |
 LL | / pub unsafe extern "C" fn no_escape4(_: usize, ap0: &mut VaListImpl, mut ap1: ...) {
 LL | |     ap0 = &mut ap1;
 LL | |
 LL | |
 LL | |
-LL | |
 LL | | }
    | |_^
 
 error[E0495]: cannot infer an appropriate lifetime for borrow expression due to conflicting requirements
-  --> $DIR/variadic-ffi-4.rs:25:11
+  --> $DIR/variadic-ffi-4.rs:24:11
    |
 LL |     ap0 = &mut ap1;
    |           ^^^^^^^^
    |
-note: first, the lifetime cannot outlive the anonymous lifetime #3 defined on the function body at 24:1...
-  --> $DIR/variadic-ffi-4.rs:24:1
+note: first, the lifetime cannot outlive the scope of call-site for function at 23:83...
+  --> $DIR/variadic-ffi-4.rs:23:83
    |
-LL | / pub unsafe extern "C" fn no_escape4(_: usize, ap0: &mut VaListImpl, mut ap1: ...) {
+LL |   pub unsafe extern "C" fn no_escape4(_: usize, ap0: &mut VaListImpl, mut ap1: ...) {
+   |  ___________________________________________________________________________________^
 LL | |     ap0 = &mut ap1;
 LL | |
 LL | |
 LL | |
-LL | |
 LL | | }
    | |_^
 note: ...so that the type `core::ffi::VaListImpl<'_>` is not borrowed for too long
-  --> $DIR/variadic-ffi-4.rs:25:11
+  --> $DIR/variadic-ffi-4.rs:24:11
    |
 LL |     ap0 = &mut ap1;
    |           ^^^^^^^^
-note: but, the lifetime must be valid for the anonymous lifetime #1 defined on the function body at 24:1...
-  --> $DIR/variadic-ffi-4.rs:24:1
+note: but, the lifetime must be valid for the anonymous lifetime #1 defined on the function body at 23:1...
+  --> $DIR/variadic-ffi-4.rs:23:1
    |
 LL | / pub unsafe extern "C" fn no_escape4(_: usize, ap0: &mut VaListImpl, mut ap1: ...) {
 LL | |     ap0 = &mut ap1;
 LL | |
 LL | |
 LL | |
-LL | |
 LL | | }
    | |_^
 note: ...so that reference does not outlive borrowed content
-  --> $DIR/variadic-ffi-4.rs:25:11
+  --> $DIR/variadic-ffi-4.rs:24:11
    |
 LL |     ap0 = &mut ap1;
    |           ^^^^^^^^
 
 error[E0308]: mismatched types
-  --> $DIR/variadic-ffi-4.rs:33:12
+  --> $DIR/variadic-ffi-4.rs:31:12
    |
 LL |     *ap0 = ap1.clone();
    |            ^^^^^^^^^^^ lifetime mismatch
    |
    = note: expected type `core::ffi::VaListImpl<'_>`
               found type `core::ffi::VaListImpl<'_>`
-note: the anonymous lifetime #3 defined on the function body at 32:1...
-  --> $DIR/variadic-ffi-4.rs:32:1
+note: the scope of call-site for function at 30:87...
+  --> $DIR/variadic-ffi-4.rs:30:87
    |
-LL | / pub unsafe extern "C" fn no_escape5(_: usize, mut ap0: &mut VaListImpl, mut ap1: ...) {
+LL |   pub unsafe extern "C" fn no_escape5(_: usize, mut ap0: &mut VaListImpl, mut ap1: ...) {
+   |  _______________________________________________________________________________________^
 LL | |     *ap0 = ap1.clone();
-LL | |
 LL | | }
    | |_^
-note: ...does not necessarily outlive the anonymous lifetime #2 defined on the function body at 32:1
-  --> $DIR/variadic-ffi-4.rs:32:1
+note: ...does not necessarily outlive the anonymous lifetime #2 defined on the function body at 30:1
+  --> $DIR/variadic-ffi-4.rs:30:1
    |
 LL | / pub unsafe extern "C" fn no_escape5(_: usize, mut ap0: &mut VaListImpl, mut ap1: ...) {
 LL | |     *ap0 = ap1.clone();
-LL | |
-LL | | }
-   | |_^
-
-error[E0308]: mismatched types
-  --> $DIR/variadic-ffi-4.rs:33:12
-   |
-LL |     *ap0 = ap1.clone();
-   |            ^^^^^^^^^^^ lifetime mismatch
-   |
-   = note: expected type `core::ffi::VaListImpl<'_>`
-              found type `core::ffi::VaListImpl<'_>`
-note: the anonymous lifetime #2 defined on the function body at 32:1...
-  --> $DIR/variadic-ffi-4.rs:32:1
-   |
-LL | / pub unsafe extern "C" fn no_escape5(_: usize, mut ap0: &mut VaListImpl, mut ap1: ...) {
-LL | |     *ap0 = ap1.clone();
-LL | |
-LL | | }
-   | |_^
-note: ...does not necessarily outlive the anonymous lifetime #3 defined on the function body at 32:1
-  --> $DIR/variadic-ffi-4.rs:32:1
-   |
-LL | / pub unsafe extern "C" fn no_escape5(_: usize, mut ap0: &mut VaListImpl, mut ap1: ...) {
-LL | |     *ap0 = ap1.clone();
-LL | |
 LL | | }
    | |_^
 
-error: aborting due to 11 previous errors
+error: aborting due to 8 previous errors
 
-Some errors have detailed explanations: E0308, E0621.
-For more information about an error, try `rustc --explain E0308`.
+For more information about this error, try `rustc --explain E0308`.
diff --git a/src/test/ui/error-codes/E0617.rs b/src/test/ui/error-codes/E0617.rs
index 439c3db5768..c832e09ac11 100644
--- a/src/test/ui/error-codes/E0617.rs
+++ b/src/test/ui/error-codes/E0617.rs
@@ -1,5 +1,3 @@
-// ignore-tidy-linelength
-
 extern {
     fn printf(c: *const i8, ...);
 }
@@ -22,7 +20,7 @@ fn main() {
         //~^ ERROR can't pass `u16` to variadic function
         //~| HELP cast the value to `c_uint`
         printf(::std::ptr::null(), printf);
-        //~^ ERROR can't pass `for<'r> unsafe extern "C" fn(*const i8, std::ffi::VaListImpl<'r>, ...) {printf}` to variadic function
-        //~| HELP cast the value to `for<'r> unsafe extern "C" fn(*const i8, std::ffi::VaListImpl<'r>, ...)`
+        //~^ ERROR can't pass `unsafe extern "C" fn(*const i8, ...) {printf}` to variadic function
+        //~| HELP cast the value to `unsafe extern "C" fn(*const i8, ...)`
     }
 }
diff --git a/src/test/ui/error-codes/E0617.stderr b/src/test/ui/error-codes/E0617.stderr
index d866320bbcd..7c4df099d0d 100644
--- a/src/test/ui/error-codes/E0617.stderr
+++ b/src/test/ui/error-codes/E0617.stderr
@@ -1,42 +1,42 @@
 error[E0617]: can't pass `f32` to variadic function
-  --> $DIR/E0617.rs:9:36
+  --> $DIR/E0617.rs:7:36
    |
 LL |         printf(::std::ptr::null(), 0f32);
    |                                    ^^^^ help: cast the value to `c_double`: `0f32 as c_double`
 
 error[E0617]: can't pass `i8` to variadic function
-  --> $DIR/E0617.rs:12:36
+  --> $DIR/E0617.rs:10:36
    |
 LL |         printf(::std::ptr::null(), 0i8);
    |                                    ^^^ help: cast the value to `c_int`: `0i8 as c_int`
 
 error[E0617]: can't pass `i16` to variadic function
-  --> $DIR/E0617.rs:15:36
+  --> $DIR/E0617.rs:13:36
    |
 LL |         printf(::std::ptr::null(), 0i16);
    |                                    ^^^^ help: cast the value to `c_int`: `0i16 as c_int`
 
 error[E0617]: can't pass `u8` to variadic function
-  --> $DIR/E0617.rs:18:36
+  --> $DIR/E0617.rs:16:36
    |
 LL |         printf(::std::ptr::null(), 0u8);
    |                                    ^^^ help: cast the value to `c_uint`: `0u8 as c_uint`
 
 error[E0617]: can't pass `u16` to variadic function
-  --> $DIR/E0617.rs:21:36
+  --> $DIR/E0617.rs:19:36
    |
 LL |         printf(::std::ptr::null(), 0u16);
    |                                    ^^^^ help: cast the value to `c_uint`: `0u16 as c_uint`
 
-error[E0617]: can't pass `for<'r> unsafe extern "C" fn(*const i8, std::ffi::VaListImpl<'r>, ...) {printf}` to variadic function
-  --> $DIR/E0617.rs:24:36
+error[E0617]: can't pass `unsafe extern "C" fn(*const i8, ...) {printf}` to variadic function
+  --> $DIR/E0617.rs:22:36
    |
 LL |         printf(::std::ptr::null(), printf);
    |                                    ^^^^^^
-help: cast the value to `for<'r> unsafe extern "C" fn(*const i8, std::ffi::VaListImpl<'r>, ...)`
+help: cast the value to `unsafe extern "C" fn(*const i8, ...)`
    |
-LL |         printf(::std::ptr::null(), printf as for<'r> unsafe extern "C" fn(*const i8, std::ffi::VaListImpl<'r>, ...));
-   |                                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |         printf(::std::ptr::null(), printf as unsafe extern "C" fn(*const i8, ...));
+   |                                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to 6 previous errors
 
diff --git a/src/test/ui/symbol-names/impl1.legacy.stderr b/src/test/ui/symbol-names/impl1.legacy.stderr
index c1d22a919d9..a3d966bb0b0 100644
--- a/src/test/ui/symbol-names/impl1.legacy.stderr
+++ b/src/test/ui/symbol-names/impl1.legacy.stderr
@@ -46,26 +46,26 @@ error: def-path(bar::<impl foo::Foo>::baz)
 LL |         #[rustc_def_path]
    |         ^^^^^^^^^^^^^^^^^
 
-error: symbol-name(_ZN198_$LT$$u5b$$RF$dyn$u20$impl1..Foo$u2b$Assoc$u20$$u3d$$u20$extern$u20$$u22$C$u22$$u20$fn$LP$$RF$u8$RP$$u2b$impl1..AutoTrait$u3b$$u20$_$u5d$$u20$as$u20$impl1..main..$u7b$$u7b$closure$u7d$$u7d$..Bar$GT$6method17h6f205aef6a8ccc7bE)
-  --> $DIR/impl1.rs:63:13
+error: symbol-name(_ZN209_$LT$$u5b$$RF$dyn$u20$impl1..Foo$u2b$Assoc$u20$$u3d$$u20$extern$u20$$u22$C$u22$$u20$fn$LP$$RF$u8$C$$u20$...$RP$$u2b$impl1..AutoTrait$u3b$$u20$_$u5d$$u20$as$u20$impl1..main..$u7b$$u7b$closure$u7d$$u7d$..Bar$GT$6method17h059bf53000885489E)
+  --> $DIR/impl1.rs:61:13
    |
 LL |             #[rustc_symbol_name]
    |             ^^^^^^^^^^^^^^^^^^^^
 
-error: demangling(<[&dyn impl1::Foo+Assoc = extern "C" fn(&u8)+impl1::AutoTrait; _] as impl1::main::{{closure}}::Bar>::method::h6f205aef6a8ccc7b)
-  --> $DIR/impl1.rs:63:13
+error: demangling(<[&dyn impl1::Foo+Assoc = extern "C" fn(&u8, ::.)+impl1::AutoTrait; _] as impl1::main::{{closure}}::Bar>::method::h059bf53000885489)
+  --> $DIR/impl1.rs:61:13
    |
 LL |             #[rustc_symbol_name]
    |             ^^^^^^^^^^^^^^^^^^^^
 
-error: demangling-alt(<[&dyn impl1::Foo+Assoc = extern "C" fn(&u8)+impl1::AutoTrait; _] as impl1::main::{{closure}}::Bar>::method)
-  --> $DIR/impl1.rs:63:13
+error: demangling-alt(<[&dyn impl1::Foo+Assoc = extern "C" fn(&u8, ::.)+impl1::AutoTrait; _] as impl1::main::{{closure}}::Bar>::method)
+  --> $DIR/impl1.rs:61:13
    |
 LL |             #[rustc_symbol_name]
    |             ^^^^^^^^^^^^^^^^^^^^
 
-error: def-path(<[&dyn Foo<Assoc = for<'r> extern "C" fn(&'r u8)> + AutoTrait; _] as main::{{closure}}#1::Bar>::method)
-  --> $DIR/impl1.rs:70:13
+error: def-path(<[&dyn Foo<Assoc = for<'r> extern "C" fn(&'r u8, ...)> + AutoTrait; _] as main::{{closure}}#1::Bar>::method)
+  --> $DIR/impl1.rs:68:13
    |
 LL |             #[rustc_def_path]
    |             ^^^^^^^^^^^^^^^^^
diff --git a/src/test/ui/symbol-names/impl1.rs b/src/test/ui/symbol-names/impl1.rs
index 137b72dcd9c..add0d10ea6c 100644
--- a/src/test/ui/symbol-names/impl1.rs
+++ b/src/test/ui/symbol-names/impl1.rs
@@ -57,19 +57,17 @@ fn main() {
         }
 
         // Test type mangling, by putting them in an `impl` header.
-        // FIXME(eddyb) test C varargs when `core::ffi::VaListImpl` stops leaking into the signature
-        // (which is a problem because `core` has an unpredictable hash) - see also #44930.
-        impl Bar for [&'_ (dyn Foo<Assoc = extern fn(&u8, /*...*/)> + AutoTrait); 3] {
+        impl Bar for [&'_ (dyn Foo<Assoc = extern fn(&u8, ...)> + AutoTrait); 3] {
             #[rustc_symbol_name]
-            //[legacy]~^ ERROR symbol-name(_ZN198_$LT$$u5b$$RF$dyn$u20$impl1..Foo$u2b$Assoc$u20$$u3d$$u20$extern$u20$$u22$C$u22$$u20$fn$LP$$RF$u8$RP$$u2b$impl1..AutoTrait$u3b$$u20$_$u5d$$u20$as$u20$impl1..main..$u7b$$u7b$closure$u7d$$u7d$..Bar$GT$6method
-            //[legacy]~| ERROR demangling(<[&dyn impl1::Foo+Assoc = extern "C" fn(&u8)+impl1::AutoTrait; _] as impl1::main::{{closure}}::Bar>::method
-            //[legacy]~| ERROR demangling-alt(<[&dyn impl1::Foo+Assoc = extern "C" fn(&u8)+impl1::AutoTrait; _] as impl1::main::{{closure}}::Bar>::method)
-             //[v0]~^^^^ ERROR symbol-name(_RNvXNCNvCs4fqI2P2rA04_5impl14mains_0ARDNtB6_3Foop5AssocFG_KCRL0_hEuNtB6_9AutoTraitEL_j3_NtB2_3Bar6method)
-                //[v0]~| ERROR demangling(<[&dyn impl1[317d481089b8c8fe]::Foo<Assoc = for<'a> extern "C" fn(&'a u8)> + impl1[317d481089b8c8fe]::AutoTrait; 3: usize] as impl1[317d481089b8c8fe]::main::{closure#1}::Bar>::method)
-                //[v0]~| ERROR demangling-alt(<[&dyn impl1::Foo<Assoc = for<'a> extern "C" fn(&'a u8)> + impl1::AutoTrait; 3] as impl1::main::{closure#1}::Bar>::method)
+            //[legacy]~^ ERROR symbol-name(_ZN209_$LT$$u5b$$RF$dyn$u20$impl1..Foo$u2b$Assoc$u20$$u3d$$u20$extern$u20$$u22$C$u22$$u20$fn$LP$$RF$u8$C$$u20$...$RP$$u2b$impl1..AutoTrait$u3b$$u20$_$u5d$$u20$as$u20$impl1..main..$u7b$$u7b$closure$u7d$$u7d$..Bar$GT$6method
+            //[legacy]~| ERROR demangling(<[&dyn impl1::Foo+Assoc = extern "C" fn(&u8, ::.)+impl1::AutoTrait; _] as impl1::main::{{closure}}::Bar>::method
+            //[legacy]~| ERROR demangling-alt(<[&dyn impl1::Foo+Assoc = extern "C" fn(&u8, ::.)+impl1::AutoTrait; _] as impl1::main::{{closure}}::Bar>::method)
+             //[v0]~^^^^ ERROR symbol-name(_RNvXNCNvCs4fqI2P2rA04_5impl14mains_0ARDNtB6_3Foop5AssocFG_KCRL0_hvEuNtB6_9AutoTraitEL_j3_NtB2_3Bar6method)
+                //[v0]~| ERROR demangling(<[&dyn impl1[317d481089b8c8fe]::Foo<Assoc = for<'a> extern "C" fn(&'a u8, ...)> + impl1[317d481089b8c8fe]::AutoTrait; 3: usize] as impl1[317d481089b8c8fe]::main::{closure#1}::Bar>::method)
+                //[v0]~| ERROR demangling-alt(<[&dyn impl1::Foo<Assoc = for<'a> extern "C" fn(&'a u8, ...)> + impl1::AutoTrait; 3] as impl1::main::{closure#1}::Bar>::method)
             #[rustc_def_path]
-            //[legacy]~^ ERROR def-path(<[&dyn Foo<Assoc = for<'r> extern "C" fn(&'r u8)> + AutoTrait; _] as main::{{closure}}#1::Bar>::method)
-               //[v0]~^^ ERROR def-path(<[&dyn Foo<Assoc = for<'r> extern "C" fn(&'r u8)> + AutoTrait; _] as main::{{closure}}#1::Bar>::method)
+            //[legacy]~^ ERROR def-path(<[&dyn Foo<Assoc = for<'r> extern "C" fn(&'r u8, ...)> + AutoTrait; _] as main::{{closure}}#1::Bar>::method)
+               //[v0]~^^ ERROR def-path(<[&dyn Foo<Assoc = for<'r> extern "C" fn(&'r u8, ...)> + AutoTrait; _] as main::{{closure}}#1::Bar>::method)
             fn method(&self) {}
         }
     };
diff --git a/src/test/ui/symbol-names/impl1.v0.stderr b/src/test/ui/symbol-names/impl1.v0.stderr
index e024799df86..01fe39ddf6c 100644
--- a/src/test/ui/symbol-names/impl1.v0.stderr
+++ b/src/test/ui/symbol-names/impl1.v0.stderr
@@ -46,26 +46,26 @@ error: def-path(bar::<impl foo::Foo>::baz)
 LL |         #[rustc_def_path]
    |         ^^^^^^^^^^^^^^^^^
 
-error: symbol-name(_RNvXNCNvCs4fqI2P2rA04_5impl14mains_0ARDNtB6_3Foop5AssocFG_KCRL0_hEuNtB6_9AutoTraitEL_j3_NtB2_3Bar6method)
-  --> $DIR/impl1.rs:63:13
+error: symbol-name(_RNvXNCNvCs4fqI2P2rA04_5impl14mains_0ARDNtB6_3Foop5AssocFG_KCRL0_hvEuNtB6_9AutoTraitEL_j3_NtB2_3Bar6method)
+  --> $DIR/impl1.rs:61:13
    |
 LL |             #[rustc_symbol_name]
    |             ^^^^^^^^^^^^^^^^^^^^
 
-error: demangling(<[&dyn impl1[317d481089b8c8fe]::Foo<Assoc = for<'a> extern "C" fn(&'a u8)> + impl1[317d481089b8c8fe]::AutoTrait; 3: usize] as impl1[317d481089b8c8fe]::main::{closure#1}::Bar>::method)
-  --> $DIR/impl1.rs:63:13
+error: demangling(<[&dyn impl1[317d481089b8c8fe]::Foo<Assoc = for<'a> extern "C" fn(&'a u8, ...)> + impl1[317d481089b8c8fe]::AutoTrait; 3: usize] as impl1[317d481089b8c8fe]::main::{closure#1}::Bar>::method)
+  --> $DIR/impl1.rs:61:13
    |
 LL |             #[rustc_symbol_name]
    |             ^^^^^^^^^^^^^^^^^^^^
 
-error: demangling-alt(<[&dyn impl1::Foo<Assoc = for<'a> extern "C" fn(&'a u8)> + impl1::AutoTrait; 3] as impl1::main::{closure#1}::Bar>::method)
-  --> $DIR/impl1.rs:63:13
+error: demangling-alt(<[&dyn impl1::Foo<Assoc = for<'a> extern "C" fn(&'a u8, ...)> + impl1::AutoTrait; 3] as impl1::main::{closure#1}::Bar>::method)
+  --> $DIR/impl1.rs:61:13
    |
 LL |             #[rustc_symbol_name]
    |             ^^^^^^^^^^^^^^^^^^^^
 
-error: def-path(<[&dyn Foo<Assoc = for<'r> extern "C" fn(&'r u8)> + AutoTrait; _] as main::{{closure}}#1::Bar>::method)
-  --> $DIR/impl1.rs:70:13
+error: def-path(<[&dyn Foo<Assoc = for<'r> extern "C" fn(&'r u8, ...)> + AutoTrait; _] as main::{{closure}}#1::Bar>::method)
+  --> $DIR/impl1.rs:68:13
    |
 LL |             #[rustc_def_path]
    |             ^^^^^^^^^^^^^^^^^