[LLDB] Add negative number parsing to DIL (#144557)

Author: kuilpd

lldb/source/ValueObject/DILParser.cpp

@@ -348,8 +348,15 @@ void DILParser::BailOut(const std::string &error, uint32_t loc,
 //    ? Integer constant ?
 //
 std::optional<int64_t> DILParser::ParseIntegerConstant() {
-  auto spelling = CurToken().GetSpelling();
-  llvm::StringRef spelling_ref = spelling;
+  std::string number_spelling;
+  if (CurToken().GetKind() == Token::minus) {
+    // StringRef::getAsInteger<>() can parse negative numbers.
+    // FIXME: Remove this once unary minus operator is added.
+    number_spelling = "-";
+    m_dil_lexer.Advance();
+  }
+  number_spelling.append(CurToken().GetSpelling());
+  llvm::StringRef spelling_ref = number_spelling;
   int64_t raw_value;
   if (!spelling_ref.getAsInteger<int64_t>(0, raw_value)) {
     m_dil_lexer.Advance();

lldb/test/API/commands/frame/var-dil/basics/ArraySubscript/TestFrameVarDILArraySubscript.py

@@ -60,11 +60,7 @@ def test_subscript(self):
         self.expect_var_path("*(&int_arr[1])", value="2")
 
         # Test for negative index.
-        self.expect(
-            "frame var 'int_arr[-1]'",
-            error=True,
-            substrs=["failed to parse integer constant"],
-        )
+        self.expect_var_path("int_ptr_1[-1]", True, value="1")
 
         # Test for floating point index
         self.expect(

lldb/test/API/commands/frame/var-dil/basics/ArraySubscript/main.cpp

@@ -3,6 +3,7 @@
 int main(int argc, char **argv) {
   int int_arr[] = {1, 2, 3};
   int *int_ptr = int_arr;
+  int *int_ptr_1 = &int_arr[1];
   int(&int_arr_ref)[3] = int_arr;
   void *p_void = (void *)int_arr;