[mlir][sparse] Improving error-detection for `STEA::get{Pos,Crd}Type`

[aartbik]

mlir/include/mlir/Dialect/SparseTensor/IR/SparseTensorAttrDefs.td

302

no need for these comments

mlir/include/mlir/Dialect/SparseTensor/IR/SparseTensorAttrDefs.td

AttrBuilder<(ins "ArrayRef<::mlir::sparse_tensor::DimLevelType>":$lvlTypes,
                          higherOrdering,
                          posWidth,
                          crdWidth,
                          ArrayRef<::mlir::sparse_tensor::SparseTensorDimSliceAttr>{});
     }]>
   ];
 
   let extraClassDeclaration = [{
-    /// Returns the type for position storage based on posWidth
+    /// Returns the type for position storage based on posWidth.
+    /// Asserts that the encoding is non-null (since there's nowhere
+    /// to get the `MLIRContext` from).
     Type getPosType() const;
 
-    /// Returns the type for coordinate storage based on crdWidth
+    /// Returns the type for coordinate storage based on crdWidth.
+    /// Asserts that the encoding is non-null (since there's nowhere
+    /// to get the `MLIRContext` from).
     Type getCrdType() const;
 
     /// Constructs a new encoding with the dimOrdering and higherOrdering
     /// reset to the default/identity.
     SparseTensorEncodingAttr withoutOrdering() const;
 
     /// Constructs a new encoding with the pointer and index bitwidth
     /// reset to the default.

mlir/lib/Dialect/SparseTensor/IR/SparseTensorDialect.cpp

 Type mlir::sparse_tensor::detail::getIntegerOrIndexType(MLIRContext *ctx,
                                                         unsigned bitwidth) {
   if (bitwidth)
     return IntegerType::get(ctx, bitwidth);
   return IndexType::get(ctx);
 }
 
 Type SparseTensorEncodingAttr::getPosType() const {
+  assert(getImpl() && "Uninitialized SparseTensorEncodingAttr");
   return detail::getIntegerOrIndexType(getContext(), getPosWidth());
 }
 
 Type SparseTensorEncodingAttr::getCrdType() const {
+  assert(getImpl() && "Uninitialized SparseTensorEncodingAttr");
   return detail::getIntegerOrIndexType(getContext(), getCrdWidth());
 }
 
 SparseTensorEncodingAttr SparseTensorEncodingAttr::withoutOrdering() const {
   return SparseTensorEncodingAttr::get(getContext(), getLvlTypes(), AffineMap(),
                                        AffineMap(), getPosWidth(),
                                        getCrdWidth());
 }