Use "generator" instead of "future" when appropriate

Author: tmandry

src/librustc_trait_selection/traits/error_reporting/suggestions.rs

@@ -1166,13 +1166,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
     ) {
         let source_map = self.tcx.sess.source_map();
 
-        let is_async_fn = self
-            .tcx
-            .parent(inner_generator)
-            .map(|parent_did| self.tcx.asyncness(parent_did))
-            .map(|parent_asyncness| parent_asyncness == hir::IsAsync::Async)
-            .unwrap_or(false);
-        let is_async_move = self
+        let is_async = self
             .tcx
             .hir()
             .as_local_hir_id(inner_generator)
@@ -1184,7 +1178,8 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                 _ => false,
             })
             .unwrap_or(false);
-        let await_or_yield = if is_async_fn || is_async_move { "await" } else { "yield" };
+        let await_or_yield = if is_async { "await" } else { "yield" };
+        let future_or_generator = if is_async { "future" } else { "generator" };
 
         // Special case the primary error message when send or sync is the trait that was
         // not implemented.
@@ -1197,7 +1192,8 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
 
             err.clear_code();
             err.set_primary_message(format!(
-                "future cannot be {} between threads safely",
+                "{} cannot be {} between threads safely",
+                future_or_generator,
                 trait_verb
             ));
 
@@ -1220,14 +1216,18 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                             format!("future created by async closure is not {}", trait_name),
                     }
                 ))
-                .unwrap_or_else(|| format!("future is not {}", trait_name));
+                .unwrap_or_else(|| format!("{} is not {}", future_or_generator, trait_name));
 
             span.push_span_label(original_span, message);
             err.set_span(span);
 
-            format!("is not {}", trait_name)
+            format!("{} is not {}", future_or_generator, trait_name)
         } else {
-            format!("does not implement `{}`", trait_ref.print_only_trait_path())
+            format!(
+                "{} does not implement `{}`",
+                future_or_generator,
+                trait_ref.print_only_trait_path()
+            )
         };
 
         // Look at the last interior type to get a span for the `.await`.
@@ -1255,10 +1255,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
 
         err.span_note(
             span,
-            &format!(
-                "future {} as this value is used across an {}",
-                trait_explanation, await_or_yield,
-            ),
+            &format!("{} as this value is used across an {}", trait_explanation, await_or_yield),
         );
 
         if let Some(expr_id) = expr {

src/test/ui/generator/issue-68112.rs

@@ -31,7 +31,7 @@ fn test1() {
         yield;
     };
     require_send(send_gen);
-    //~^ ERROR future cannot be sent between threads
+    //~^ ERROR generator cannot be sent between threads
 }
 
 pub fn make_gen2<T>(t: T) -> impl Generator<Return = T> {

src/test/ui/generator/issue-68112.stderr

@@ -1,4 +1,4 @@
-error: future cannot be sent between threads safely
+error: generator cannot be sent between threads safely
   --> $DIR/issue-68112.rs:33:5
    |
 LL | fn require_send(_: impl Send) {}
@@ -8,7 +8,7 @@ LL |     require_send(send_gen);
    |     ^^^^^^^^^^^^ generator is not `Send`
    |
    = help: the trait `std::marker::Sync` is not implemented for `std::cell::RefCell<i32>`
-note: future is not `Send` as this value is used across an yield
+note: generator is not `Send` as this value is used across an yield
   --> $DIR/issue-68112.rs:31:9
    |
 LL |         let _non_send_gen = make_non_send_generator();

src/test/ui/generator/not-send-sync.rs

@@ -7,7 +7,7 @@ fn main() {
     fn assert_send<T: Send>(_: T) {}
 
     assert_sync(|| {
-        //~^ ERROR: future cannot be shared between threads safely
+        //~^ ERROR: generator cannot be shared between threads safely
         let a = Cell::new(2);
         yield;
     });

src/test/ui/generator/not-send-sync.stderr

@@ -11,7 +11,7 @@ LL |     assert_send(|| {
    = note: required because of the requirements on the impl of `std::marker::Send` for `&std::cell::Cell<i32>`
    = note: required because it appears within the type `[generator@$DIR/not-send-sync.rs:16:17: 20:6 a:&std::cell::Cell<i32> _]`
 
-error: future cannot be shared between threads safely
+error: generator cannot be shared between threads safely
   --> $DIR/not-send-sync.rs:9:5
    |
 LL |     fn assert_sync<T: Sync>(_: T) {}
@@ -21,7 +21,7 @@ LL |     assert_sync(|| {
    |     ^^^^^^^^^^^ generator is not `Sync`
    |
    = help: within `[generator@$DIR/not-send-sync.rs:9:17: 13:6 {std::cell::Cell<i32>, ()}]`, the trait `std::marker::Sync` is not implemented for `std::cell::Cell<i32>`
-note: future is not `Sync` as this value is used across an yield
+note: generator is not `Sync` as this value is used across an yield
   --> $DIR/not-send-sync.rs:12:9
    |
 LL |         let a = Cell::new(2);