fail loudly on unsized by-ref invariants (#1644) #1758

Job	Run time
abi_cafe (ubuntu-24.04-arm, aarch64-unknown-linux-gnu)	4m 55s
abi_cafe (ubuntu-latest, x86_64-unknown-linux-gnu)	4m 55s
abi_cafe (macos-latest, aarch64-apple-darwin)	5m 1s
abi_cafe (macos-15-intel, x86_64-apple-darwin)	4m 36s
abi_cafe (windows-latest, x86_64-pc-windows-msvc)	4m 51s
abi_cafe (ubuntu-latest, x86_64-unknown-linux-gnu)	6m 42s
abi_cafe (macos-15-intel, x86_64-apple-darwin)	16m 54s
abi_cafe (macos-latest, aarch64-apple-darwin)	3m 59s
abi_cafe (ubuntu-24.04-arm, aarch64-unknown-linux-gnu)	5m 19s
abi_cafe (windows-latest, x86_64-pc-windows-msvc)	9m 29s
	1h 6m 41s

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