[mlir] Check nullity of MixedContainerType and TypedArrayAttrBase

[Chia-hungDuan]

Summary

It's valid to create a TypedArrayAttr or MixedContainerType with
nullptr, e.g.,
  std::vector<mlir::Attribute> attrs = {mlir::StringAttr()};
  builder.createArrayAttr(attrs);

The predicate didn't check if it's a nullptr and it ends up a crash in
the attribute static verifier. We always check if an attribute is null
so it's better to align the check for these two container type attr.

[mehdi_amini]

Can you add more context / motivation in the revision description?

[Chia-hungDuan]

Add descriptions

mlir/include/mlir/IR/OpBase.td

 // ContainerType) can hold elements with a mix of types. Requires a call that
 // produces a list of all elements' types.
 class MixedContainerType<Type etype, Pred containerPred, code elementTypesCall,
                          string descr> :
     Type<
         And<[
             containerPred,
             Concat<
-                "::llvm::all_of(" # elementTypesCall # ", [](Type t) { return ",
+                "::llvm::all_of(" # elementTypesCall # ", [](Type t) { "
+                "return t && (",
                 SubstLeaves<"$_self", "t", etype.predicate>,
-                "; })"
+                "); })"
             >
         ]>,
         descr # " with any combination of " # etype.summary # " values"> {
   // The type of elements in the container.
   Type elementType = etype;
 
   // Call to retrieve.
   code getElementTypesCall = elementTypesCall;

 // Base class for array attributes whose elements are of the same kind.
 // `element` specifies the element attribute kind stored in this array.
 class TypedArrayAttrBase<Attr element, string summary>: ArrayAttrBase<
     And<[
       // Guarantee this is an ArrayAttr first
       CPred<"$_self.isa<::mlir::ArrayAttr>()">,
       // Guarantee all elements satisfy the constraints from `element`
       Concat<"::llvm::all_of($_self.cast<::mlir::ArrayAttr>(), "
-                            "[&](::mlir::Attribute attr) { return ",
+                            "[&](::mlir::Attribute attr) { return attr && (",
                                SubstLeaves<"$_self", "attr", element.predicate>,
-                            "; })">]>,
+                            "); })">]>,
     summary> {
 
   Attr elementAttr = element;
 }
 
 def AffineMapArrayAttr : TypedArrayAttrBase<AffineMapAttr,
                                       "AffineMap array attribute"> {
   let constBuilderCall = "$_builder.getAffineMapArrayAttr($0)";

mlir/test/mlir-tblgen/op-attribute.td

 // DEF: if (tblgen_i64_attr && !(((tblgen_i64_attr.isa<::mlir::IntegerAttr>())) && ((tblgen_i64_attr.cast<::mlir::IntegerAttr>().getType().isSignlessInteger(64)))))
 // DEF: if (tblgen_f32_attr && !(((tblgen_f32_attr.isa<::mlir::FloatAttr>())) && ((tblgen_f32_attr.cast<::mlir::FloatAttr>().getType().isF32()))))
 // DEF: if (tblgen_f64_attr && !(((tblgen_f64_attr.isa<::mlir::FloatAttr>())) && ((tblgen_f64_attr.cast<::mlir::FloatAttr>().getType().isF64()))))
 // DEF: if (tblgen_str_attr && !((tblgen_str_attr.isa<::mlir::StringAttr>())))
 // DEF: if (tblgen_elements_attr && !((tblgen_elements_attr.isa<::mlir::ElementsAttr>())))
 // DEF: if (tblgen_function_attr && !((tblgen_function_attr.isa<::mlir::FlatSymbolRefAttr>())))
 // DEF: if (tblgen_some_type_attr && !(((tblgen_some_type_attr.isa<::mlir::TypeAttr>())) && ((tblgen_some_type_attr.cast<::mlir::TypeAttr>().getValue().isa<SomeType>()))))
 // DEF: if (tblgen_array_attr && !((tblgen_array_attr.isa<::mlir::ArrayAttr>())))
-// DEF: if (tblgen_some_attr_array && !(((tblgen_some_attr_array.isa<::mlir::ArrayAttr>())) && (::llvm::all_of(tblgen_some_attr_array.cast<::mlir::ArrayAttr>(), [&](::mlir::Attribute attr) { return (some-condition); }))))
+// DEF: if (tblgen_some_attr_array && !(((tblgen_some_attr_array.isa<::mlir::ArrayAttr>())) && (::llvm::all_of(tblgen_some_attr_array.cast<::mlir::ArrayAttr>(), [&](::mlir::Attribute attr) { return attr && ((some-condition)); }))))
 // DEF: if (tblgen_type_attr && !(((tblgen_type_attr.isa<::mlir::TypeAttr>())) && ((tblgen_type_attr.cast<::mlir::TypeAttr>().getValue().isa<::mlir::Type>()))))
 
 // Test common attribute kind getters' return types
 // ---
 
 // DEF: ::mlir::Attribute BOp::any_attr()
 // DEF: bool BOp::bool_attr()
 // DEF: uint32_t BOp::i32_attr()