Do not ICE in if without else in async fn

src/librustc_typeck/check/generator_interior.rs

@@ -244,7 +244,13 @@ impl<'a, 'tcx> Visitor<'tcx> for InteriorVisitor<'a, 'tcx> {
         // can be reborrowed without needing to spill to a temporary.
         // If this were not the case, then we could conceivably have
         // to create intermediate temporaries.)
-        let ty = self.fcx.tables.borrow().expr_ty(expr);
-        self.record(ty, scope, Some(expr), expr.span);
+        //
+        // The type table might not have information for this expression
+        // if it is in a malformed scope. (#66387)
+        if let Some(ty) = self.fcx.tables.borrow().expr_ty_opt(expr) {
+            self.record(ty, scope, Some(expr), expr.span);
+        } else {
+            self.fcx.tcx.sess.delay_span_bug(expr.span, "no type for node");
+        }
     }
 }

src/test/ui/async-await/issue-66387-if-without-else.rs

@@ -0,0 +1,10 @@
+// edition:2018
+async fn f() -> i32 {
+    if true { //~ ERROR if may be missing an else clause
+        return 0;
+    }
+    // An `if` block without `else` causes the type table not to have a type for this expr.
+    // Check that we do not unconditionally access the type table and we don't ICE.
+}
+
+fn main() {}

src/test/ui/async-await/issue-66387-if-without-else.stderr

@@ -0,0 +1,16 @@
+error[E0317]: if may be missing an else clause
+  --> $DIR/issue-66387-if-without-else.rs:3:5
+   |
+LL | /     if true {
+LL | |         return 0;
+LL | |     }
+   | |_____^ expected (), found i32
+   |
+   = note: expected type `()`
+              found type `i32`
+   = note: `if` expressions without `else` evaluate to `()`
+   = help: consider adding an `else` block that evaluates to the expected type
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0317`.