[mlir] Print bad size in AttrSizedOperandSegments

[modocache]

Summary

When printing verification errors for ops with the incorrect number of
operand segments, print the required number as well as the actual
number. Split off from D93005.

mlir/test/IR/traits.mlir

 func @failedResultSizeAttrWrongTotalSize() {
   // expected-error @+1 {{result count (4) does not match with the total size (3) specified in attribute 'result_segment_sizes'}}
   %0:4 = "test.attr_sized_results"() {result_segment_sizes = dense<[0, 1, 1, 1]>: vector<4xi32>} : () -> (i32, i32, i32, i32)
 }
 
 // -----
 
 func @failedResultSizeAttrWrongCount() {
-  // expected-error @+1 {{'result_segment_sizes' attribute for specifying result segments must have 4 elements}}
+  // expected-error @+1 {{'result_segment_sizes' attribute for specifying result segments must have 4 elements, but got 3}}
   %0:4 = "test.attr_sized_results"() {result_segment_sizes = dense<[2, 1, 1]>: vector<3xi32>} : () -> (i32, i32, i32, i32)
 }
 
 // -----
 
 func @succeededResultSizeAttr() {
   // CHECK: test.attr_sized_results
   %0:4 = "test.attr_sized_results"() {result_segment_sizes = dense<[0, 2, 1, 1]>: vector<4xi32>} : () -> (i32, i32, i32, i32)

mlir/tools/mlir-tblgen/OpDefinitionsGen.cpp

void OpOperandAdaptorEmitter::addVerification() {
   auto &body = method->body();
 
   const char *checkAttrSizedValueSegmentsCode = R"(
   {
     auto sizeAttr = odsAttrs.get("{0}").cast<::mlir::DenseIntElementsAttr>();
     auto numElements = sizeAttr.getType().cast<::mlir::ShapedType>().getNumElements();
     if (numElements != {1})
       return emitError(loc, "'{0}' attribute for specifying {2} segments "
-                       "must have {1} elements");
+                       "must have {1} elements, but got ") << numElements;
   }
   )";
 
   // Verify a few traits first so that we can use
   // getODSOperands()/getODSResults() in the rest of the verifier.
   for (auto &trait : op.getTraits()) {
     if (auto *t = dyn_cast<tblgen::NativeOpTrait>(&trait)) {
       if (t->getTrait() == "::mlir::OpTrait::AttrSizedOperandSegments") {