Log dtype names on input dtype mismatch (#7537)

Summary:
Update the error message when input tensor scalar type is incorrect. We've seen this get hit a few times and it should be easier to debug than it is.

New Message:
```
[method.cpp:825] Input 0 has unexpected scalar type: expected Float but was Byte.
```
Old Message:
```
[method.cpp:826] The 0-th input tensor's scalartype does not meet requirement: found 0 but expected 6
```


Test Plan:
Built executorch bento kernel locally and tested with an incorrect scalar type to view the new error message.
```
[method.cpp:825] Input 0 has unexpected scalar type: expected Float but was Byte.
```

Reviewed By: digantdesai, SS-JIA

Differential Revision: D67887770

Pulled By: GregoryComer

Author: GregoryComer

runtime/core/exec_aten/util/scalar_type_util.cpp

@@ -0,0 +1,21 @@
+#include <executorch/runtime/core/exec_aten/util/scalar_type_util.h>
+
+namespace executorch {
+namespace runtime {
+
+const char* scalar_type_to_string(::executorch::aten::ScalarType t) {
+#define DEFINE_CASE(unused, name)            \
+  case ::executorch::aten::ScalarType::name: \
+    return #name;
+
+  switch (t) {
+    ET_FORALL_SCALAR_TYPES(DEFINE_CASE)
+    default:
+      return "Unknown";
+  }
+
+#undef DEFINE_CASE
+}
+
+} // namespace runtime
+} // namespace executorch

runtime/core/exec_aten/util/scalar_type_util.h

@@ -1294,6 +1294,11 @@ struct promote_types {
                   CTYPE_ALIAS,                                              \
                   __VA_ARGS__))
 
+/**
+ * Return a string representation of a ScalarType value.
+ */
+const char* scalar_type_to_string(::executorch::aten::ScalarType t);
+
 } // namespace runtime
 } // namespace executorch
 

runtime/core/exec_aten/util/targets.bzl

@@ -19,7 +19,7 @@ def define_common_targets():
 
         runtime.cxx_library(
             name = "scalar_type_util" + aten_suffix,
-            srcs = [],
+            srcs = ["scalar_type_util.cpp"],
             exported_headers = [
                 "scalar_type_util.h",
             ],

runtime/core/portable_type/targets.bzl

@@ -49,6 +49,7 @@ def define_common_targets():
             "scalar_type.h",
             "qint_types.h",
             "bits_types.h",
+            "string_view.h",
         ],
         visibility = [
             "//executorch/extension/...",

runtime/executor/method.cpp

@@ -819,11 +819,10 @@ Method::set_input(const EValue& input_evalue, size_t input_idx) {
     ET_CHECK_OR_RETURN_ERROR(
         t_dst.scalar_type() == t_src.scalar_type(),
         InvalidArgument,
-        "The %zu-th input tensor's scalartype does not meet requirement: found %" PRId8
-        " but expected %" PRId8,
+        "Input %zu has unexpected scalar type: expected %s but was %s.",
         input_idx,
-        static_cast<int8_t>(t_src.scalar_type()),
-        static_cast<int8_t>(t_dst.scalar_type()));
+        scalar_type_to_string(t_dst.scalar_type()),
+        scalar_type_to_string(t_src.scalar_type()));
     // Reset the shape for the Method's input as the size of forwarded input
     // tensor for shape dynamism. Also is a safety check if need memcpy.
     Error err = resize_tensor(t_dst, t_src.sizes());

runtime/executor/targets.bzl

@@ -82,6 +82,7 @@ def define_common_targets():
                 "//executorch/runtime/core:evalue" + aten_suffix,
                 "//executorch/runtime/core:event_tracer" + aten_suffix,
                 "//executorch/runtime/core/exec_aten:lib" + aten_suffix,
+                "//executorch/runtime/core/exec_aten/util:scalar_type_util" + aten_suffix,
                 "//executorch/runtime/core/exec_aten/util:tensor_util" + aten_suffix,
                 "//executorch/runtime/kernel:kernel_runtime_context" + aten_suffix,
                 "//executorch/runtime/kernel:operator_registry",