Type-check aliasing in separate pass #1977
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One piece of functionality is missing: all variables are now reported as unused, because the alias checking machinery did double duty as a usage checker. That'll need its own mechanism now. |
razetime
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Jul 16, 2023
This significantly simplifies the type checker, and also fixes known (and future) bugs related to tracking aliases of an incompletely typed term. This also allows us to provide better error messages, although it's possible that they are currently slightly worse, as the aliasing checking does not use the "context" mechanism of the term-level type checker. The AST itself is simplified because it no longer has to embed alias information (which wasn't correct anyway, and was not actually used). There is one user-visible change: lambdas that must return an alias-free result will now require a return type annotation. We may loosen this in the future, but it is a very rare case in practice. Closes diku-dk#1872.
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This significantly simplifies the type checker, and also fixes known
(and future) bugs related to tracking aliases of an incompletely typed
term.
This also allows us to provide better error messages, although it's
possible that they are currently slightly worse, as the aliasing
checking does not use the "context" mechanism of the term-level type
checker.
The AST itself is simplified because it no longer has to embed alias
information (which wasn't correct anyway, and was not actually used).
There is one user-visible change: lambdas that must return an
alias-free result will now require a return type annotation. We may
loosen this in the future, but it is a very rare case in practice.
Closes #1872.