Implement IR generation for records.

[todo]

descartes/lib/Semantic.cpp

Lines 338 to 342 in fafccc9

	// TODO: Implement IR generation for records.
	return {nullptr, memberType};
	}
	}
	throw SemanticError("Can't find the right member on the record type");

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This issue was generated by todo based on a TODO comment in fafccc9 when #52 was merged. cc @tetsuo-cpp.