[clang] [CIR] Upstream CIR method attribute handling (PR #174640)

[Erich Keane via cfe-commits]

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@@ -301,6 +301,50 @@ DataMemberAttr::verify(function_ref<InFlightDiagnostic()> emitError,
   return success();
 }
 
+//===----------------------------------------------------------------------===//
+// MethodAttr definitions
+//===----------------------------------------------------------------------===//
+
+Attribute MethodAttr::parse(AsmParser &parser, Type odsType) {
+  auto ty = mlir::cast<cir::MethodType>(odsType);
+
+  if (parser.parseLess().failed())
+    return {};
+
+  // Try to parse the null pointer constant.
+  if (parser.parseOptionalKeyword("null").succeeded()) {
+    if (parser.parseGreater())
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erichkeane wrote:

should this be `parser.parseGreater.failed()` ? Like we do above?

https://github.com/llvm/llvm-project/pull/174640