Merge pull request #69653 from DougGregor/try-question-bang-never

Make sure we record "Never" as the thrown error type for try!/try?

Author: DougGregor

lib/Sema/TypeCheckEffects.cpp

@@ -3104,6 +3104,8 @@ class CheckEffectsCoverage : public EffectsHandlingWalker<CheckEffectsCoverage>
 
     if (auto thrownError = TypeChecker::canThrow(Ctx, E->getSubExpr())) {
       E->setThrownError(*thrownError);
+    } else {
+      E->setThrownError(Ctx.getNeverType());
     }
 
     scope.preserveCoverageFromOptionalOrForcedTryOperand();
@@ -3123,6 +3125,8 @@ class CheckEffectsCoverage : public EffectsHandlingWalker<CheckEffectsCoverage>
 
     if (auto thrownError = TypeChecker::canThrow(Ctx, E->getSubExpr())) {
       E->setThrownError(*thrownError);
+    } else {
+      E->setThrownError(Ctx.getNeverType());
     }
 
     scope.preserveCoverageFromOptionalOrForcedTryOperand();

test/stmt/typed_throws_ast.swift

@@ -37,3 +37,15 @@ func throwsAnything() throws {
   // CHECK: optional_try_expr{{.*}}thrown_error="MyError"
   try? printOrFail("ssshhhhh")
 }
+
+func doesNotThrow() { }
+
+func throwsNothing() {
+  // CHECK-LABE: func_decl{{.*}}"throwsNothing()"
+
+  // CHECK: force_try_expr{{.*}}thrown_error="Never"
+  try! doesNotThrow()
+
+  // CHECK: optional_try_expr{{.*}}thrown_error="Never"
+  try? doesNotThrow()
+}