Enable assertion the lhs.typ() and rhs.typ() are equal for assignments

[danielsn]

Description of changes:

RMC had a workaround because some tests failed when we asserted that assignments must have matching types. The underlying bugs appear to have been fixed, so enable the assertion

Resolved issues:

Resolves #95

Call-outs:

Testing:

• How is this change tested? Existing regression suite

• Is this a refactor change? No

Checklist

• Each commit message has a non-empty body, explaining why the change was made
• Methods or procedures are documented
• Regression or unit tests are included, or existing tests cover the modified code
• My PR is restricted to a single feature or bugfix

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