Add a version of TypeBandwidth that returns a status on error. (#95)

Co-authored-by: PINS Team <[email protected]>

p4_constraints/BUILD.bazel

@@ -14,7 +14,6 @@ cc_library(
         ":ast_cc_proto",
         "//gutils:proto",
         "//gutils:status",
-        "@com_google_absl//absl/base:log_severity",
         "@com_google_absl//absl/container:flat_hash_map",
         "@com_google_absl//absl/container:flat_hash_set",
         "@com_google_absl//absl/log",

p4_constraints/ast.cc

@@ -28,6 +28,7 @@
 #include "google/protobuf/descriptor.h"
 #include "google/protobuf/util/message_differencer.h"
 #include "gutils/proto.h"
+#include "gutils/status_builder.h"
 #include "gutils/status_macros.h"
 #include "p4_constraints/ast.pb.h"
 
@@ -117,6 +118,16 @@ absl::optional<int> TypeBitwidth(const Type& type) {
   }
 }
 
+absl::StatusOr<int> TypeBitwidthOrStatus(const Type& type) {
+  std::optional<int> bitwidth = TypeBitwidth(type);
+  if (bitwidth.has_value()) {
+    return *bitwidth;
+  } else {
+    return gutils::InvalidArgumentErrorBuilder(GUTILS_LOC)
+           << "expected a type with bitwidth, but got: " << type;
+  }
+}
+
 bool SetTypeBitwidth(Type* type, int bitwidth) {
   switch (type->type_case()) {
     case Type::kFixedUnsigned:

p4_constraints/ast.h

@@ -53,6 +53,10 @@ bool TypeHasOrdering(const Type& type);
 // Returns bit-width of the given type, provided the type is fixed-size.
 absl::optional<int> TypeBitwidth(const Type& type);
 
+// Returns bit-width of the given type, provided the type is fixed-size.
+// Otherwise returns an InvalidArgumentError.
+absl::StatusOr<int> TypeBitwidthOrStatus(const ast::Type& type);
+
 // Sets bitwidth of the given type, provided the type is fixed-size, or does
 // nothing otherwise. Returns `true` in the former case and `false` in the
 // latter case.