The attribute is the layout description. The runtime takes the struct's single field and repeats it for the length passed to InlineArrayAttribute, and the InlineArrayAttribute documentation treats that attribute as the only mechanism that should define the total repeated shape [17][4]. Eight ints, 32 bytes on a normal .NET 10 target [5]. Divide it out and each element is 4 bytes [16], which is exactly the Size = 4 the dev.to writeup ends up putting on an element struct in its second fix [13]. So in this example the two declarations agree. .NET 10 refuses the type anyway, because any interpretation of duplicate size information would be ambiguous, where earlier runtimes allowed implementation-specific behaviour [3][2].
The audit in the writeup has two steps [15]. Scanning source and generated interop code for types carrying both attributes is the cheap one, and it misses the case that hurts: the shape can already be baked into a referenced assembly, where nothing in your build mentions it, and the first code to force the load may be reflection, interop registration, or serialization [7]. Hence step two, loading every relevant plugin and interop assembly in a .NET 10 test process [15]. A successful build tells you the compiler agreed with you; the loader gets a separate vote.
Deleting the Size attribute makes the exception go away and takes an interop assumption with it, which is why the writeup declines to do that blindly [11]. The number meant one of two things. If 32 bytes described the whole native buffer, leave InlineArray(8) on the inner struct and put Size = 32 on a wrapper whose only field is that array [12]. If it described one native element, put the size on the element type and let InlineArray(8) repeat it [13]. Guessing downward has its own failure mode: the StructLayout size reference warns that an explicit size must be at least as large as the type's fields [14].
Whether the 32 transfers to your codebase depends on where it came from. In the sample it is sizeof(int) times eight and nothing more [16]. In real interop the byte count usually came from a C header with its padding included, so the assertion worth copying is the one the sample automates: Unsafe.SizeOf<T>() and fixed values proving each replacement is still 32 bytes and still supports all eight indexed values, with identical output on repeated runs [9].
The best engineering in the post is the fixture. Rather than ship a deliberately broken assembly, it builds the invalid metadata at runtime with Reflection.Emit: DefineType with typesize 32, an InlineArrayAttribute(8) custom attribute, one private int field named _element0, and CreateTypeInfo as the call that throws on .NET 10 [8]. Keeping the bad shape behind that loader boundary is what makes the exception catchable at all, because a broken type referenced directly across a test executable can be forced while the runtime compiles a method, before control reaches the intended try block [10]. That detail generalises past this rule. Any test that asserts on a load-time failure needs the failure isolated from the code doing the asserting.
