[Continuations] Trap on suspending through JS, don't throw a JS exception (#8419)

We should not be able to catch such an error. This now matches
V8's behavior.

Fixes #8416

Author: kripken

src/tools/execution-results.h

@@ -341,9 +341,10 @@ struct LoggingExternalInterface : public ShellExternalInterface {
 
     // Call the function.
     auto flow = doCall(arguments);
-    // Suspending through JS is not valid.
+    // Suspending through JS is not valid. This traps - it does not throw a
+    // catchable JS exception.
     if (flow.suspendTag) {
-      throwJSException();
+      trap("suspend through JS");
     }
     return flow.values;
   }

test/lit/exec/cont_export.wast

@@ -24,7 +24,7 @@
 
   ;; CHECK:      [fuzz-exec] calling call-call-export
   ;; CHECK-NEXT: [LoggingExternalInterface logging 10]
-  ;; CHECK-NEXT: [exception thrown: imported-js-tag externref(0)]
+  ;; CHECK-NEXT: [trap suspend through JS]
   (func $call-call-export (export "call-call-export")
     ;; Call suspend as an export. We cannot suspend through JS, so we throw.
     (call $call-export
@@ -35,7 +35,7 @@
 
   ;; CHECK:      [fuzz-exec] calling handled
   ;; CHECK-NEXT: [LoggingExternalInterface logging 10]
-  ;; CHECK-NEXT: [exception thrown: imported-js-tag externref(0)]
+  ;; CHECK-NEXT: [trap suspend through JS]
   (func $handled (export "handled")
     ;; As above, but inside a continuation, so it would be handled - if we could
     ;; suspend though JS. But we can't, so we throw.

test/lit/exec/cont_export_throw.wast

@@ -22,7 +22,7 @@
  )
 
  ;; CHECK:      [fuzz-exec] calling handled
- ;; CHECK-NEXT: [exception thrown: imported-js-tag externref(0)]
+ ;; CHECK-NEXT: [trap suspend through JS]
  (func $handled (export "handled")
   (drop
    (block $block (result (ref $cont))

test/lit/exec/cont_many_unhandled_2.wast

@@ -35,7 +35,7 @@
  )
 
  ;; CHECK:      [fuzz-exec] calling call-suspend
- ;; CHECK-NEXT: [exception thrown: unhandled suspend]
+ ;; CHECK-NEXT: [trap suspend through JS]
  (func $call-suspend (export "call-suspend")
   (drop
    (call $call-export-catch

test/lit/exec/cont_through_js.wast

@@ -0,0 +1,59 @@
+;; NOTE: Assertions have been generated by update_lit_checks.py --output=fuzz-exec and should not be edited.
+
+;; RUN: foreach %s %t wasm-opt -all --fuzz-exec-before -q -o /dev/null 2>&1 | filecheck %s
+
+;; $test will try to suspend through JS. That traps. If it threw a JS exception
+;; instead, we would catch that exception and continue onwards, hitting an
+;; invalid internal state.
+
+(module
+ (type $f (func))
+ (type $k (cont $f))
+
+ (import "fuzzing-support" "call-export" (func $call-export (param i32 i32)))
+ (import "fuzzing-support" "call-export-catch" (func $call-export-catch (param i32) (result i32)))
+
+ (tag $e)
+
+ ;; CHECK:      [fuzz-exec] calling suspend
+ ;; CHECK-NEXT: [exception thrown: unhandled suspend]
+ (func $suspend (export "suspend")
+  (suspend $e)
+ )
+
+ ;; CHECK:      [fuzz-exec] calling handle
+ ;; CHECK-NEXT: [trap suspend through JS]
+ (func $handle (export "handle")
+  (drop
+   (block $block (result (ref $k))
+    (resume $k (on $e $block)
+     (cont.new $k
+      (ref.func $suspend-after-host-frame)
+     )
+    )
+    (return)
+   )
+  )
+ )
+
+ (func $suspend-after-host-frame (type $f)
+  (call $call-export
+   (i32.const 0) ;; "suspend"
+   (i32.const 0)
+  )
+ )
+
+ ;; CHECK:      [fuzz-exec] calling test
+ ;; CHECK-NEXT: [trap suspend through JS]
+ (func $test (export "test")
+  (drop
+   (call $call-export-catch
+    (i32.const 1) ;; "handle"
+   )
+  )
+  (call $call-export
+   (i32.const 0) ;; "suspend"
+   (i32.const 1) ;; rethrow exceptions
+  )
+ )
+)