[Lldb-commits] [lldb] [LLDB] Add field member operators to DIL (PR #138093)

[Pavel Labath via lldb-commits]

================
@@ -272,4 +272,66 @@ Interpreter::Visit(const UnaryOpNode *node) {
       m_expr, "invalid ast: unexpected binary operator", node->GetLocation());
 }
 
+llvm::Expected<lldb::ValueObjectSP>
+Interpreter::Visit(const MemberOfNode *node) {
+  Status error;
+  auto base_or_err = Evaluate(node->GetBase());
+  if (!base_or_err) {
+    return base_or_err;
+  }
+  lldb::ValueObjectSP base = *base_or_err;
+
+  // Perform basic type checking.
+  CompilerType base_type = base->GetCompilerType();
+  // When using an arrow, make sure the base is a pointer or array type.
+  // When using a period, make sure the base type is NOT a pointer type.
+  if (node->GetIsArrow() && !base_type.IsPointerType() &&
+      !base_type.IsArrayType()) {
+    lldb::ValueObjectSP deref_sp = base->Dereference(error);
+    if (error.Success()) {
+      base = deref_sp;
+      base_type = deref_sp->GetCompilerType().GetPointerType();
+    } else {
+      std::string errMsg =
+          llvm::formatv("member reference type {0} is not a pointer; "
+                        "did you mean to use '.'?",
+                        base_type.TypeDescription());
+      return llvm::make_error<DILDiagnosticError>(
+          m_expr, errMsg, node->GetLocation(), node->GetFieldName().size());
+    }
+  } else if (!node->GetIsArrow() && base_type.IsPointerType()) {
+    std::string errMsg =
+        llvm::formatv("member reference type {0} is a pointer; "
+                      "did you mean to use '->'?",
+                      base_type.TypeDescription());
+    return llvm::make_error<DILDiagnosticError>(
+        m_expr, errMsg, node->GetLocation(), node->GetFieldName().size());
+  }
+
+  // User specified array->elem; need to get to element[0] to look for fields.
+  if (node->GetIsArrow() && base_type.IsArrayType())
+    base = base->GetChildAtIndex(0);
+
+  // Now look for the member with the specified name.
+  lldb::ValueObjectSP field_obj =
+      base->GetChildMemberWithName(llvm::StringRef(node->GetFieldName()));
+  if (field_obj && field_obj->GetName().GetString() == node->GetFieldName()) {
+    if (field_obj->GetCompilerType().IsReferenceType()) {
+      lldb::ValueObjectSP tmp_obj = field_obj->Dereference(error);
----------------
labath wrote:

Why is this necessary? GetChildMemberWithName seems to work just fine on references:
```
(lldb) script lldb.frame.FindVariable("b")
(A &) b = 0x00007fffffffd7e8: {
  X = 42
  x = 0x00007fffffffd7e8
}
(lldb) script lldb.frame.FindVariable("b").GetChildMemberWithName("X")
(int) X = 42
```

https://github.com/llvm/llvm-project/pull/138093