From 77503578e1e727228ce47dd7847302936cf80a23 Mon Sep 17 00:00:00 2001
From: Yuki Okushi <huyuumi.dev@gmail.com>
Date: Sat, 30 May 2020 18:48:54 +0900
Subject: [PATCH] Return early to avoid ICE

---
 .../traits/error_reporting/suggestions.rs     |  6 ++++++
 src/librustc_trait_selection/traits/mod.rs    |  7 -------
 src/test/ui/suggestions/issue-72766.rs        | 20 +++++++++++++++++++
 src/test/ui/suggestions/issue-72766.stderr    | 15 ++++++++++++++
 .../clippy/clippy_lints/src/utils/mod.rs      |  5 +++++
 5 files changed, 46 insertions(+), 7 deletions(-)
 create mode 100644 src/test/ui/suggestions/issue-72766.rs
 create mode 100644 src/test/ui/suggestions/issue-72766.stderr

diff --git a/src/librustc_trait_selection/traits/error_reporting/suggestions.rs b/src/librustc_trait_selection/traits/error_reporting/suggestions.rs
index 31992f29808..3174f43c657 100644
--- a/src/librustc_trait_selection/traits/error_reporting/suggestions.rs
+++ b/src/librustc_trait_selection/traits/error_reporting/suggestions.rs
@@ -1909,6 +1909,12 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
 
                 let self_ty = self.resolve_vars_if_possible(&trait_ref.self_ty());
 
+                // Do not check on infer_types to avoid panic in evaluate_obligation.
+                if self_ty.has_infer_types() {
+                    return;
+                }
+                let self_ty = self.tcx.erase_regions(&self_ty);
+
                 let impls_future = self.tcx.type_implements_trait((
                     future_trait,
                     self_ty,
diff --git a/src/librustc_trait_selection/traits/mod.rs b/src/librustc_trait_selection/traits/mod.rs
index b45de72ab02..958ba69a826 100644
--- a/src/librustc_trait_selection/traits/mod.rs
+++ b/src/librustc_trait_selection/traits/mod.rs
@@ -540,13 +540,6 @@ fn type_implements_trait<'tcx>(
         trait_def_id, ty, params, param_env
     );
 
-    // Do not check on infer_types to avoid panic in evaluate_obligation.
-    if ty.has_infer_types() {
-        return false;
-    }
-
-    let ty = tcx.erase_regions(&ty);
-
     let trait_ref = ty::TraitRef { def_id: trait_def_id, substs: tcx.mk_substs_trait(ty, params) };
 
     let obligation = Obligation {
diff --git a/src/test/ui/suggestions/issue-72766.rs b/src/test/ui/suggestions/issue-72766.rs
new file mode 100644
index 00000000000..0448f071958
--- /dev/null
+++ b/src/test/ui/suggestions/issue-72766.rs
@@ -0,0 +1,20 @@
+// edition:2018
+// compile-flags: -Cincremental=tmp/issue-72766
+
+pub struct SadGirl;
+
+impl SadGirl {
+    pub async fn call(&self) -> Result<(), ()> {
+        Ok(())
+    }
+}
+
+async fn async_main() -> Result<(), ()> {
+    // should be `.call().await?`
+    SadGirl {}.call()?; //~ ERROR: the `?` operator can only be applied to values
+    Ok(())
+}
+
+fn main() {
+    let _ = async_main();
+}
diff --git a/src/test/ui/suggestions/issue-72766.stderr b/src/test/ui/suggestions/issue-72766.stderr
new file mode 100644
index 00000000000..4290f3b4bf1
--- /dev/null
+++ b/src/test/ui/suggestions/issue-72766.stderr
@@ -0,0 +1,15 @@
+error[E0277]: the `?` operator can only be applied to values that implement `std::ops::Try`
+  --> $DIR/issue-72766.rs:14:5
+   |
+LL |     SadGirl {}.call()?;
+   |     ^^^^^^^^^^^^^^^^^^
+   |     |
+   |     the `?` operator cannot be applied to type `impl std::future::Future`
+   |     help: consider using `.await` here: `SadGirl {}.call().await?`
+   |
+   = help: the trait `std::ops::Try` is not implemented for `impl std::future::Future`
+   = note: required by `std::ops::Try::into_result`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0277`.
diff --git a/src/tools/clippy/clippy_lints/src/utils/mod.rs b/src/tools/clippy/clippy_lints/src/utils/mod.rs
index 6c1488664bf..6dd8fef7e82 100644
--- a/src/tools/clippy/clippy_lints/src/utils/mod.rs
+++ b/src/tools/clippy/clippy_lints/src/utils/mod.rs
@@ -323,6 +323,11 @@ pub fn implements_trait<'a, 'tcx>(
     trait_id: DefId,
     ty_params: &[GenericArg<'tcx>],
 ) -> bool {
+    // Do not check on infer_types to avoid panic in evaluate_obligation.
+    if ty.has_infer_types() {
+        return false;
+    }
+    let ty = cx.tcx.erase_regions(&ty);
     let ty_params = cx.tcx.mk_substs(ty_params.iter());
     cx.tcx.type_implements_trait((trait_id, ty, ty_params, cx.param_env))
 }