Rollup merge of #104788 - compiler-errors:unresolved-ct-in-gen, r=fee1-dead

Do not record unresolved const vars in generator interior

Don't record types in the generator interior when we see unresolved const variables.

We already do this for associated types -- this is important to avoid unresolved inference variables in the generator results during writeback, since the writeback results get stable hashed in incremental mode.

Fixes #104787

2 files changed, 92 insertions, 0 deletions

diff --git a/src/test/ui/generator/unresolved-ct-var.rs b/src/test/ui/generator/unresolved-ct-var.rs
new file mode 100644
index 00000000000..0a1570fc239
--- /dev/null
+++ b/src/test/ui/generator/unresolved-ct-var.rs
@@ -0,0 +1,14 @@
+// incremental
+// edition:2021
+
+fn main() {
+    let _ = async {
+        let s = std::array::from_fn(|_| ()).await;
+        //~^ ERROR `[(); _]` is not a future
+        //~| ERROR type inside `async` block must be known in this context
+        //~| ERROR type inside `async` block must be known in this context
+        //~| ERROR type inside `async` block must be known in this context
+        //~| ERROR type inside `async` block must be known in this context
+        //~| ERROR type inside `async` block must be known in this context
+    };
+}
diff --git a/src/test/ui/generator/unresolved-ct-var.stderr b/src/test/ui/generator/unresolved-ct-var.stderr
new file mode 100644
index 00000000000..fdf00dfad7a
--- /dev/null
+++ b/src/test/ui/generator/unresolved-ct-var.stderr
@@ -0,0 +1,78 @@
+error[E0277]: `[(); _]` is not a future
+  --> $DIR/unresolved-ct-var.rs:6:44
+   |
+LL |         let s = std::array::from_fn(|_| ()).await;
+   |                 ---------------------------^^^^^^
+   |                 |                          |
+   |                 |                          `[(); _]` is not a future
+   |                 |                          help: remove the `.await`
+   |                 this call returns `[(); _]`
+   |
+   = help: the trait `Future` is not implemented for `[(); _]`
+   = note: [(); _] must be a future or must implement `IntoFuture` to be awaited
+   = note: required for `[(); _]` to implement `IntoFuture`
+
+error[E0698]: type inside `async` block must be known in this context
+  --> $DIR/unresolved-ct-var.rs:6:17
+   |
+LL |         let s = std::array::from_fn(|_| ()).await;
+   |                 ^^^^^^^^^^^^^^^^^^^ cannot infer the value of const parameter `N` declared on the function `from_fn`
+   |
+note: the type is part of the `async` block because of this `await`
+  --> $DIR/unresolved-ct-var.rs:6:44
+   |
+LL |         let s = std::array::from_fn(|_| ()).await;
+   |                                            ^^^^^^
+
+error[E0698]: type inside `async` block must be known in this context
+  --> $DIR/unresolved-ct-var.rs:6:17
+   |
+LL |         let s = std::array::from_fn(|_| ()).await;
+   |                 ^^^^^^^^^^^^^^^^^^^ cannot infer the value of const parameter `N` declared on the function `from_fn`
+   |
+note: the type is part of the `async` block because of this `await`
+  --> $DIR/unresolved-ct-var.rs:6:44
+   |
+LL |         let s = std::array::from_fn(|_| ()).await;
+   |                                            ^^^^^^
+
+error[E0698]: type inside `async` block must be known in this context
+  --> $DIR/unresolved-ct-var.rs:6:17
+   |
+LL |         let s = std::array::from_fn(|_| ()).await;
+   |                 ^^^^^^^^^^^^^^^^^^^ cannot infer the value of const parameter `N` declared on the function `from_fn`
+   |
+note: the type is part of the `async` block because of this `await`
+  --> $DIR/unresolved-ct-var.rs:6:44
+   |
+LL |         let s = std::array::from_fn(|_| ()).await;
+   |                                            ^^^^^^
+
+error[E0698]: type inside `async` block must be known in this context
+  --> $DIR/unresolved-ct-var.rs:6:17
+   |
+LL |         let s = std::array::from_fn(|_| ()).await;
+   |                 ^^^^^^^^^^^^^^^^^^^ cannot infer the value of const parameter `N` declared on the function `from_fn`
+   |
+note: the type is part of the `async` block because of this `await`
+  --> $DIR/unresolved-ct-var.rs:6:44
+   |
+LL |         let s = std::array::from_fn(|_| ()).await;
+   |                                            ^^^^^^
+
+error[E0698]: type inside `async` block must be known in this context
+  --> $DIR/unresolved-ct-var.rs:6:17
+   |
+LL |         let s = std::array::from_fn(|_| ()).await;
+   |                 ^^^^^^^^^^^^^^^^^^^ cannot infer the value of const parameter `N` declared on the function `from_fn`
+   |
+note: the type is part of the `async` block because of this `await`
+  --> $DIR/unresolved-ct-var.rs:6:44
+   |
+LL |         let s = std::array::from_fn(|_| ()).await;
+   |                                            ^^^^^^
+
+error: aborting due to 6 previous errors
+
+Some errors have detailed explanations: E0277, E0698.
+For more information about an error, try `rustc --explain E0277`.