diff --git a/mlir/include/mlir/Dialect/SparseTensor/IR/SparseTensorAttrDefs.td b/mlir/include/mlir/Dialect/SparseTensor/IR/SparseTensorAttrDefs.td
--- a/mlir/include/mlir/Dialect/SparseTensor/IR/SparseTensorAttrDefs.td
+++ b/mlir/include/mlir/Dialect/SparseTensor/IR/SparseTensorAttrDefs.td
@@ -293,10 +293,14 @@
   ];
 
   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
diff --git a/mlir/lib/Dialect/SparseTensor/IR/SparseTensorDialect.cpp b/mlir/lib/Dialect/SparseTensor/IR/SparseTensorDialect.cpp
--- a/mlir/lib/Dialect/SparseTensor/IR/SparseTensorDialect.cpp
+++ b/mlir/lib/Dialect/SparseTensor/IR/SparseTensorDialect.cpp
@@ -254,10 +254,12 @@
 }
 
 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());
 }