Tidy up

Author: iainsmith

Sources/WasmKit/Execution/Instructions/Misc.swift

@@ -21,13 +21,11 @@ extension Execution {
 extension Execution {
     mutating func refNull(sp: Sp, immediate: Instruction.RefNullOperand) {
         let value: Value
-        switch immediate.type {
+        switch immediate.type.heapType {
         case .externRef:
             value = .ref(.extern(nil))
         case .funcRef:
             value = .ref(.function(nil))
-        default:
-            fatalError()
         }
         sp[immediate.result] = UntypedValue(value)
     }

Sources/WasmKit/Execution/UntypedValue.swift

@@ -114,13 +114,11 @@ struct UntypedValue: Equatable, Hashable {
             guard storage & Self.isNullMaskPattern == 0 else { return nil }
             return Int(storage)
         }
-        switch type {
+        switch type.heapType {
         case .funcRef:
             return .function(decodeOptionalInt())
         case .externRef:
             return .extern(decodeOptionalInt())
-        default:
-            fatalError()
         }
     }
 

Sources/WasmKit/Validator.swift

@@ -333,8 +333,6 @@ struct ModuleValidator {
 extension WasmTypes.Reference {
     /// Checks if the reference type matches the expected type.
     func checkType(_ type: WasmTypes.ReferenceType) throws {
-
-        // Should we validate nonNull variants have associated values present?
         switch (self, type) {
         case (.function, .funcRef): return
         case (.extern, .externRef): return