Auto merge of #71923 - csmoe:issue-70818, r=tmandry

Check non-Send/Sync upvars captured by generator

Closes #70818
r? @tmandry

3 files changed, 167 insertions, 108 deletions

diff --git a/src/librustc_trait_selection/traits/error_reporting/suggestions.rs b/src/librustc_trait_selection/traits/error_reporting/suggestions.rs
index bd58e86988a..b8771d59dd4 100644
--- a/src/librustc_trait_selection/traits/error_reporting/suggestions.rs
+++ b/src/librustc_trait_selection/traits/error_reporting/suggestions.rs
@@ -25,6 +25,14 @@ use std::fmt;
 use super::InferCtxtPrivExt;
 use crate::traits::query::evaluate_obligation::InferCtxtExt as _;
 
+#[derive(Debug)]
+pub enum GeneratorInteriorOrUpvar {
+    // span of interior type
+    Interior(Span),
+    // span of upvar
+    Upvar(Span),
+}
+
 // This trait is public to expose the diagnostics methods to clippy.
 pub trait InferCtxtExt<'tcx> {
     fn suggest_restricting_param_bound(
@@ -128,11 +136,8 @@ pub trait InferCtxtExt<'tcx> {
     fn note_obligation_cause_for_async_await(
         &self,
         err: &mut DiagnosticBuilder<'_>,
-        target_span: Span,
-        scope_span: &Option<Span>,
-        await_span: Span,
-        expr: Option<hir::HirId>,
-        snippet: String,
+        interior_or_upvar_span: GeneratorInteriorOrUpvar,
+        interior_extra_info: Option<(Option<Span>, Span, Option<hir::HirId>, Option<Span>)>,
         inner_generator_body: Option<&hir::Body<'_>>,
         outer_generator: Option<DefId>,
         trait_ref: ty::TraitRef<'_>,
@@ -140,7 +145,6 @@ pub trait InferCtxtExt<'tcx> {
         tables: &ty::TypeckTables<'_>,
         obligation: &PredicateObligation<'tcx>,
         next_code: Option<&ObligationCauseCode<'tcx>>,
-        from_awaited_ty: Option<Span>,
     );
 
     fn note_obligation_cause_code<T>(
@@ -1205,7 +1209,6 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                 obligation.cause.span={:?}",
             obligation.predicate, obligation.cause.span
         );
-        let source_map = self.tcx.sess.source_map();
         let hir = self.tcx.hir();
 
         // Attempt to detect an async-await error by looking at the obligation causes, looking
@@ -1354,7 +1357,23 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
             );
             eq
         };
-        let target_span = tables
+
+        let mut interior_or_upvar_span = None;
+        let mut interior_extra_info = None;
+
+        if let Some(upvars) = self.tcx.upvars(generator_did) {
+            interior_or_upvar_span = upvars.iter().find_map(|(upvar_id, upvar)| {
+                let upvar_ty = tables.node_type(*upvar_id);
+                let upvar_ty = self.resolve_vars_if_possible(&upvar_ty);
+                if ty_matches(&upvar_ty) {
+                    Some(GeneratorInteriorOrUpvar::Upvar(upvar.span))
+                } else {
+                    None
+                }
+            });
+        };
+
+        tables
             .generator_interior_types
             .iter()
             .find(|ty::GeneratorInteriorTypeCause { ty, .. }| ty_matches(ty))
@@ -1375,31 +1394,21 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                     .map(|expr| expr.span);
                 let ty::GeneratorInteriorTypeCause { span, scope_span, yield_span, expr, .. } =
                     cause;
-                (
-                    span,
-                    source_map.span_to_snippet(*span),
-                    scope_span,
-                    yield_span,
-                    expr,
-                    from_awaited_ty,
-                )
+
+                interior_or_upvar_span = Some(GeneratorInteriorOrUpvar::Interior(*span));
+                interior_extra_info = Some((*scope_span, *yield_span, *expr, from_awaited_ty));
             });
 
         debug!(
-            "maybe_note_obligation_cause_for_async_await: target_ty={:?} \
-                generator_interior_types={:?} target_span={:?}",
-            target_ty, tables.generator_interior_types, target_span
+            "maybe_note_obligation_cause_for_async_await: interior_or_upvar={:?} \
+                generator_interior_types={:?}",
+            interior_or_upvar_span, tables.generator_interior_types
         );
-        if let Some((target_span, Ok(snippet), scope_span, yield_span, expr, from_awaited_ty)) =
-            target_span
-        {
+        if let Some(interior_or_upvar_span) = interior_or_upvar_span {
             self.note_obligation_cause_for_async_await(
                 err,
-                *target_span,
-                scope_span,
-                *yield_span,
-                *expr,
-                snippet,
+                interior_or_upvar_span,
+                interior_extra_info,
                 generator_body,
                 outer_generator,
                 trait_ref,
@@ -1407,7 +1416,6 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                 tables,
                 obligation,
                 next_code,
-                from_awaited_ty,
             );
             true
         } else {
@@ -1420,11 +1428,8 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
     fn note_obligation_cause_for_async_await(
         &self,
         err: &mut DiagnosticBuilder<'_>,
-        target_span: Span,
-        scope_span: &Option<Span>,
-        yield_span: Span,
-        expr: Option<hir::HirId>,
-        snippet: String,
+        interior_or_upvar_span: GeneratorInteriorOrUpvar,
+        interior_extra_info: Option<(Option<Span>, Span, Option<hir::HirId>, Option<Span>)>,
         inner_generator_body: Option<&hir::Body<'_>>,
         outer_generator: Option<DefId>,
         trait_ref: ty::TraitRef<'_>,
@@ -1432,7 +1437,6 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
         tables: &ty::TypeckTables<'_>,
         obligation: &PredicateObligation<'tcx>,
         next_code: Option<&ObligationCauseCode<'tcx>>,
-        from_awaited_ty: Option<Span>,
     ) {
         let source_map = self.tcx.sess.source_map();
 
@@ -1493,46 +1497,27 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
             format!("does not implement `{}`", trait_ref.print_only_trait_path())
         };
 
-        if let Some(await_span) = from_awaited_ty {
-            // The type causing this obligation is one being awaited at await_span.
-            let mut span = MultiSpan::from_span(await_span);
-
-            span.push_span_label(
-                await_span,
-                format!("await occurs here on type `{}`, which {}", target_ty, trait_explanation),
-            );
-
-            err.span_note(
-                span,
-                &format!(
-                    "future {not_trait} as it awaits another future which {not_trait}",
-                    not_trait = trait_explanation
-                ),
-            );
-        } else {
-            // Look at the last interior type to get a span for the `.await`.
-            debug!(
-                "note_obligation_cause_for_async_await generator_interior_types: {:#?}",
-                tables.generator_interior_types
-            );
+        let mut explain_yield = |interior_span: Span,
+                                 yield_span: Span,
+                                 scope_span: Option<Span>| {
             let mut span = MultiSpan::from_span(yield_span);
-            span.push_span_label(
-                yield_span,
-                format!("{} occurs here, with `{}` maybe used later", await_or_yield, snippet),
-            );
-
-            span.push_span_label(
-                target_span,
-                format!("has type `{}` which {}", target_ty, trait_explanation),
-            );
-
-            // If available, use the scope span to annotate the drop location.
-            if let Some(scope_span) = scope_span {
+            if let Ok(snippet) = source_map.span_to_snippet(interior_span) {
                 span.push_span_label(
-                    source_map.end_point(*scope_span),
-                    format!("`{}` is later dropped here", snippet),
+                    yield_span,
+                    format!("{} occurs here, with `{}` maybe used later", await_or_yield, snippet),
                 );
+                // If available, use the scope span to annotate the drop location.
+                if let Some(scope_span) = scope_span {
+                    span.push_span_label(
+                        source_map.end_point(scope_span),
+                        format!("`{}` is later dropped here", snippet),
+                    );
+                }
             }
+            span.push_span_label(
+                interior_span,
+                format!("has type `{}` which {}", target_ty, trait_explanation),
+            );
 
             err.span_note(
                 span,
@@ -1541,48 +1526,90 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                     future_or_generator, trait_explanation, an_await_or_yield
                 ),
             );
-        }
-
-        if let Some(expr_id) = expr {
-            let expr = hir.expect_expr(expr_id);
-            debug!("target_ty evaluated from {:?}", expr);
-
-            let parent = hir.get_parent_node(expr_id);
-            if let Some(hir::Node::Expr(e)) = hir.find(parent) {
-                let parent_span = hir.span(parent);
-                let parent_did = parent.owner.to_def_id();
-                // ```rust
-                // impl T {
-                //     fn foo(&self) -> i32 {}
-                // }
-                // T.foo();
-                // ^^^^^^^ a temporary `&T` created inside this method call due to `&self`
-                // ```
-                //
-                let is_region_borrow =
-                    tables.expr_adjustments(expr).iter().any(|adj| adj.is_region_borrow());
-
-                // ```rust
-                // struct Foo(*const u8);
-                // bar(Foo(std::ptr::null())).await;
-                //     ^^^^^^^^^^^^^^^^^^^^^ raw-ptr `*T` created inside this struct ctor.
-                // ```
-                debug!("parent_def_kind: {:?}", self.tcx.def_kind(parent_did));
-                let is_raw_borrow_inside_fn_like_call = match self.tcx.def_kind(parent_did) {
-                    DefKind::Fn | DefKind::Ctor(..) => target_ty.is_unsafe_ptr(),
-                    _ => false,
-                };
+        };
+        match interior_or_upvar_span {
+            GeneratorInteriorOrUpvar::Interior(interior_span) => {
+                if let Some((scope_span, yield_span, expr, from_awaited_ty)) = interior_extra_info {
+                    if let Some(await_span) = from_awaited_ty {
+                        // The type causing this obligation is one being awaited at await_span.
+                        let mut span = MultiSpan::from_span(await_span);
+                        span.push_span_label(
+                            await_span,
+                            format!(
+                                "await occurs here on type `{}`, which {}",
+                                target_ty, trait_explanation
+                            ),
+                        );
+                        err.span_note(
+                            span,
+                            &format!(
+                                "future {not_trait} as it awaits another future which {not_trait}",
+                                not_trait = trait_explanation
+                            ),
+                        );
+                    } else {
+                        // Look at the last interior type to get a span for the `.await`.
+                        debug!(
+                            "note_obligation_cause_for_async_await generator_interior_types: {:#?}",
+                            tables.generator_interior_types
+                        );
+                        explain_yield(interior_span, yield_span, scope_span);
+                    }
 
-                if (tables.is_method_call(e) && is_region_borrow)
-                    || is_raw_borrow_inside_fn_like_call
-                {
-                    err.span_help(
-                        parent_span,
-                        "consider moving this into a `let` \
+                    if let Some(expr_id) = expr {
+                        let expr = hir.expect_expr(expr_id);
+                        debug!("target_ty evaluated from {:?}", expr);
+
+                        let parent = hir.get_parent_node(expr_id);
+                        if let Some(hir::Node::Expr(e)) = hir.find(parent) {
+                            let parent_span = hir.span(parent);
+                            let parent_did = parent.owner.to_def_id();
+                            // ```rust
+                            // impl T {
+                            //     fn foo(&self) -> i32 {}
+                            // }
+                            // T.foo();
+                            // ^^^^^^^ a temporary `&T` created inside this method call due to `&self`
+                            // ```
+                            //
+                            let is_region_borrow = tables
+                                .expr_adjustments(expr)
+                                .iter()
+                                .any(|adj| adj.is_region_borrow());
+
+                            // ```rust
+                            // struct Foo(*const u8);
+                            // bar(Foo(std::ptr::null())).await;
+                            //     ^^^^^^^^^^^^^^^^^^^^^ raw-ptr `*T` created inside this struct ctor.
+                            // ```
+                            debug!("parent_def_kind: {:?}", self.tcx.def_kind(parent_did));
+                            let is_raw_borrow_inside_fn_like_call =
+                                match self.tcx.def_kind(parent_did) {
+                                    DefKind::Fn | DefKind::Ctor(..) => target_ty.is_unsafe_ptr(),
+                                    _ => false,
+                                };
+
+                            if (tables.is_method_call(e) && is_region_borrow)
+                                || is_raw_borrow_inside_fn_like_call
+                            {
+                                err.span_help(
+                                    parent_span,
+                                    "consider moving this into a `let` \
                         binding to create a shorter lived borrow",
-                    );
+                                );
+                            }
+                        }
+                    }
                 }
             }
+            GeneratorInteriorOrUpvar::Upvar(upvar_span) => {
+                let mut span = MultiSpan::from_span(upvar_span);
+                span.push_span_label(
+                    upvar_span,
+                    format!("has type `{}` which {}", target_ty, trait_explanation),
+                );
+                err.span_note(span, &format!("captured value {}", trait_explanation));
+            }
         }
 
         // Add a note for the item obligation that remains - normally a note pointing to the
diff --git a/src/test/ui/async-await/issue-70818.rs b/src/test/ui/async-await/issue-70818.rs
new file mode 100644
index 00000000000..0609e4fc081
--- /dev/null
+++ b/src/test/ui/async-await/issue-70818.rs
@@ -0,0 +1,9 @@
+// edition:2018
+
+use std::future::Future;
+fn foo<T: Send, U>(ty: T, ty1: U) -> impl Future<Output = (T, U)> + Send {
+//~^ Error future cannot be sent between threads safely
+    async { (ty, ty1) }
+}
+
+fn main() {}
diff --git a/src/test/ui/async-await/issue-70818.stderr b/src/test/ui/async-await/issue-70818.stderr
new file mode 100644
index 00000000000..5fb772fa10a
--- /dev/null
+++ b/src/test/ui/async-await/issue-70818.stderr
@@ -0,0 +1,23 @@
+error: future cannot be sent between threads safely
+  --> $DIR/issue-70818.rs:4:38
+   |
+LL | fn foo<T: Send, U>(ty: T, ty1: U) -> impl Future<Output = (T, U)> + Send {
+   |                                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ future created by async block is not `Send`
+LL |
+LL |     async { (ty, ty1) }
+   |     ------------------- this returned value is of type `impl std::future::Future`
+   |
+   = help: within `impl std::future::Future`, the trait `std::marker::Send` is not implemented for `U`
+note: captured value is not `Send`
+  --> $DIR/issue-70818.rs:6:18
+   |
+LL |     async { (ty, ty1) }
+   |                  ^^^ has type `U` which is not `Send`
+   = note: the return type of a function must have a statically known size
+help: consider restricting type parameter `U`
+   |
+LL | fn foo<T: Send, U: std::marker::Send>(ty: T, ty1: U) -> impl Future<Output = (T, U)> + Send {
+   |                  ^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to previous error
+