TypeChecker updates to filter bad line information.

Add additional checks in line offset computation to avoid integer
overflows for ASTs with bad postion maps.

PiperOrigin-RevId: 697761888

Author: jnthntatum

checker/internal/type_checker_impl.cc

@@ -75,21 +75,31 @@ SourceLocation ComputeSourceLocation(const AstImpl& ast, int64_t expr_id) {
     return SourceLocation{};
   }
   int32_t absolute_position = iter->second;
+  if (absolute_position < 0) {
+    return SourceLocation{};
+  }
+
+  // Find the first line offset that is greater than the absolute position.
   int32_t line_idx = -1;
+  int32_t offset = 0;
   for (int32_t i = 0; i < source_info.line_offsets().size(); ++i) {
-    int32_t offset = source_info.line_offsets()[i];
-    if (absolute_position < offset) {
+    int32_t next_offset = source_info.line_offsets()[i];
+    if (next_offset <= offset) {
+      // Line offset is not monotonically increasing, so line information is
+      // invalid.
+      return SourceLocation{};
+    }
+    if (absolute_position < next_offset) {
       line_idx = i;
       break;
     }
+    offset = next_offset;
   }
 
-  if (line_idx <= 0 || line_idx >= source_info.line_offsets().size()) {
-    return SourceLocation{1, absolute_position};
+  if (line_idx < 0 || line_idx >= source_info.line_offsets().size()) {
+    return SourceLocation{};
   }
 
-  auto offset = source_info.line_offsets()[line_idx - 1];
-
   int32_t rel_position = absolute_position - offset;
 
   return SourceLocation{line_idx + 1, rel_position};

checker/internal/type_checker_impl_test.cc

@@ -68,6 +68,7 @@ using ::testing::Eq;
 using ::testing::IsEmpty;
 using ::testing::Pair;
 using ::testing::Property;
+using ::testing::SizeIs;
 
 using AstType = ast_internal::Type;
 using Severity = TypeCheckIssue::Severity;
@@ -1281,6 +1282,63 @@ TEST(TypeCheckerImplTest, ExpectedTypeDoesntMatch) {
           "expected type 'map<string, string>' but found 'map<string, int>'")));
 }
 
+TEST(TypeCheckerImplTest, BadSourcePosition) {
+  google::protobuf::Arena arena;
+  TypeCheckEnv env(GetSharedTestingDescriptorPool());
+
+  TypeCheckerImpl impl(std::move(env));
+  ASSERT_OK_AND_ASSIGN(auto ast, MakeTestParsedAst("foo"));
+  auto& ast_impl = AstImpl::CastFromPublicAst(*ast);
+  ast_impl.source_info().mutable_positions()[1] = -42;
+  ASSERT_OK_AND_ASSIGN(ValidationResult result, impl.Check(std::move(ast)));
+  ASSERT_OK_AND_ASSIGN(auto source, NewSource("foo"));
+
+  EXPECT_FALSE(result.IsValid());
+  ASSERT_THAT(result.GetIssues(), SizeIs(1));
+
+  EXPECT_EQ(
+      result.GetIssues()[0].ToDisplayString(*source),
+      "ERROR: <input>:-1:-1: undeclared reference to 'foo' (in container '')");
+}
+
+TEST(TypeCheckerImplTest, BadLineOffsets) {
+  google::protobuf::Arena arena;
+  TypeCheckEnv env(GetSharedTestingDescriptorPool());
+
+  TypeCheckerImpl impl(std::move(env));
+  ASSERT_OK_AND_ASSIGN(auto source, NewSource("\nfoo"));
+
+  {
+    ASSERT_OK_AND_ASSIGN(auto ast, MakeTestParsedAst("\nfoo"));
+    auto& ast_impl = AstImpl::CastFromPublicAst(*ast);
+    ast_impl.source_info().mutable_line_offsets()[1] = 1;
+    ASSERT_OK_AND_ASSIGN(ValidationResult result, impl.Check(std::move(ast)));
+
+    EXPECT_FALSE(result.IsValid());
+    ASSERT_THAT(result.GetIssues(), SizeIs(1));
+
+    EXPECT_EQ(result.GetIssues()[0].ToDisplayString(*source),
+              "ERROR: <input>:-1:-1: undeclared reference to 'foo' (in "
+              "container '')");
+  }
+  {
+    ASSERT_OK_AND_ASSIGN(auto ast, MakeTestParsedAst("\nfoo"));
+    auto& ast_impl = AstImpl::CastFromPublicAst(*ast);
+    ast_impl.source_info().mutable_line_offsets().clear();
+    ast_impl.source_info().mutable_line_offsets().push_back(-1);
+    ast_impl.source_info().mutable_line_offsets().push_back(2);
+
+    ASSERT_OK_AND_ASSIGN(ValidationResult result, impl.Check(std::move(ast)));
+
+    EXPECT_FALSE(result.IsValid());
+    ASSERT_THAT(result.GetIssues(), SizeIs(1));
+
+    EXPECT_EQ(result.GetIssues()[0].ToDisplayString(*source),
+              "ERROR: <input>:-1:-1: undeclared reference to 'foo' (in "
+              "container '')");
+  }
+}
+
 TEST(TypeCheckerImplTest, ContainerLookupForMessageCreation) {
   TypeCheckEnv env(GetSharedTestingDescriptorPool());
   env.set_container("google.protobuf");