Auto merge of #78461 - TimDiekmann:vec-alloc, r=Amanieu

Add support for custom allocators in `Vec`

This follows the [roadmap](https://github.com/rust-lang/wg-allocators/issues/7) of the allocator WG to add custom allocators to collections.

r? `@Amanieu`

This pull request requires a crater run.

### Prior work:
- #71873: Crater-test to solve rust-lang/wg-allocators#1
- [`alloc-wg`](https://github.com/TimDiekmann/alloc-wg)-crate

7 files changed, 12 insertions, 10 deletions

diff --git a/src/test/ui/associated-types/defaults-wf.stderr b/src/test/ui/associated-types/defaults-wf.stderr
index f9044c2ea1b..26c85260194 100644
--- a/src/test/ui/associated-types/defaults-wf.stderr
+++ b/src/test/ui/associated-types/defaults-wf.stderr
@@ -6,7 +6,7 @@ LL |     type Ty = Vec<[u8]>;
    | 
   ::: $SRC_DIR/alloc/src/vec.rs:LL:COL
    |
-LL | pub struct Vec<T> {
+LL | pub struct Vec<T, #[unstable(feature = "allocator_api", issue = "32838")] A: AllocRef = Global> {
    |                - required by this bound in `Vec`
    |
    = help: the trait `Sized` is not implemented for `[u8]`
diff --git a/src/test/ui/bad/bad-sized.stderr b/src/test/ui/bad/bad-sized.stderr
index b9bce7fb5f4..10d12a09b25 100644
--- a/src/test/ui/bad/bad-sized.stderr
+++ b/src/test/ui/bad/bad-sized.stderr
@@ -17,7 +17,7 @@ LL |     let x: Vec<dyn Trait + Sized> = Vec::new();
    | 
   ::: $SRC_DIR/alloc/src/vec.rs:LL:COL
    |
-LL | pub struct Vec<T> {
+LL | pub struct Vec<T, #[unstable(feature = "allocator_api", issue = "32838")] A: AllocRef = Global> {
    |                - required by this bound in `Vec`
    |
    = help: the trait `Sized` is not implemented for `dyn Trait`
diff --git a/src/test/ui/const-generics/invalid-constant-in-args.rs b/src/test/ui/const-generics/invalid-constant-in-args.rs
index 38ad510e5d7..0bd9cbf4f47 100644
--- a/src/test/ui/const-generics/invalid-constant-in-args.rs
+++ b/src/test/ui/const-generics/invalid-constant-in-args.rs
@@ -1,4 +1,6 @@
+use std::cell::Cell;
+
 fn main() {
-    let _: Vec<&str, "a"> = Vec::new();
+    let _: Cell<&str, "a"> = Cell::new("");
     //~^ ERROR wrong number of generic arguments
 }
diff --git a/src/test/ui/const-generics/invalid-constant-in-args.stderr b/src/test/ui/const-generics/invalid-constant-in-args.stderr
index 5111815e002..9b8a5d1ae4f 100644
--- a/src/test/ui/const-generics/invalid-constant-in-args.stderr
+++ b/src/test/ui/const-generics/invalid-constant-in-args.stderr
@@ -1,8 +1,8 @@
 error[E0107]: wrong number of generic arguments: expected 1, found 2
-  --> $DIR/invalid-constant-in-args.rs:2:22
+  --> $DIR/invalid-constant-in-args.rs:4:23
    |
-LL |     let _: Vec<&str, "a"> = Vec::new();
-   |                      ^^^ unexpected const argument
+LL |     let _: Cell<&str, "a"> = Cell::new("");
+   |                       ^^^ unexpected const argument
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/issues/issue-20433.stderr b/src/test/ui/issues/issue-20433.stderr
index 3c14226b734..d40946ae03f 100644
--- a/src/test/ui/issues/issue-20433.stderr
+++ b/src/test/ui/issues/issue-20433.stderr
@@ -6,7 +6,7 @@ LL |     fn iceman(c: Vec<[i32]>) {}
    | 
   ::: $SRC_DIR/alloc/src/vec.rs:LL:COL
    |
-LL | pub struct Vec<T> {
+LL | pub struct Vec<T, #[unstable(feature = "allocator_api", issue = "32838")] A: AllocRef = Global> {
    |                - required by this bound in `Vec`
    |
    = help: the trait `Sized` is not implemented for `[i32]`
diff --git a/src/test/ui/type/ascription/issue-34255-1.rs b/src/test/ui/type/ascription/issue-34255-1.rs
index c0d39c59014..3aad085f089 100644
--- a/src/test/ui/type/ascription/issue-34255-1.rs
+++ b/src/test/ui/type/ascription/issue-34255-1.rs
@@ -7,7 +7,7 @@ impl Reactor {
         input_cells: Vec::new()
         //~^ ERROR cannot find value `input_cells` in this scope
         //~| ERROR parenthesized type parameters may only be used with a `Fn` trait
-        //~| ERROR wrong number of type arguments: expected 1, found 0
+        //~| ERROR wrong number of type arguments: expected at least 1, found 0
     }
 }
 
diff --git a/src/test/ui/type/ascription/issue-34255-1.stderr b/src/test/ui/type/ascription/issue-34255-1.stderr
index 7895cf77fc0..402e54d2a95 100644
--- a/src/test/ui/type/ascription/issue-34255-1.stderr
+++ b/src/test/ui/type/ascription/issue-34255-1.stderr
@@ -10,11 +10,11 @@ error[E0214]: parenthesized type parameters may only be used with a `Fn` trait
 LL |         input_cells: Vec::new()
    |                           ^^^^^ only `Fn` traits may use parentheses
 
-error[E0107]: wrong number of type arguments: expected 1, found 0
+error[E0107]: wrong number of type arguments: expected at least 1, found 0
   --> $DIR/issue-34255-1.rs:7:22
    |
 LL |         input_cells: Vec::new()
-   |                      ^^^^^^^^^^ expected 1 type argument
+   |                      ^^^^^^^^^^ expected at least 1 type argument
 
 error: aborting due to 3 previous errors