fix: wrap table literals in parentheses before indexing

[afcondon]

Hi there, i (Andrew) am submitting this PR but, full disclosure, the bug diagnosis, change and PR text were all prepared by Claude, an LLM. I watched it run the test suite and the logic seems sound so i'm pushing it upstream for your consideration. I very much hope this is helpful and not a burden.

In Lua, table constructor literals cannot be directly indexed without parentheses. The expression { ["key"] = val }["key"] is a syntax error, while ({ ["key"] = val })["key"] is valid.

This fix adds the same wrapPrec PrecAtom wrapping to VarIndex that was already applied to VarField, ensuring table literals are properly parenthesized when used with bracket indexing.

Fixes pattern matching on ADT constructors that would generate invalid Lua like:

if "Mod∷Type.Ctor" == { ["$ctor"] = "Mod∷Type.Ctor" }["$ctor"] then

Now correctly generates:

if "Mod∷Type.Ctor" == ({ ["$ctor"] = "Mod∷Type.Ctor" })["$ctor"] then

[afcondon]

btw i have another larger PR that migrates pslua to the new spago, if you want it. Also LLM generated but working for me.

[afcondon]

I see this failed CI but it was not a test that failed, the build ran out of space "copyFile: resource exhausted (No space left on device)"

[Unisay]

Hi Andrew,

I am glad you're interested in using and contributing to this project!

I see this PR delivers a fix without unit-test coverage. Please add a unit test (golden test) to demonstrate the problem being fixed (the idea is that without this fix the test should fail and in a way that is understandable)

[Copilot]

Pull request overview

This PR fixes a Lua syntax error when table constructor literals are directly indexed with bracket notation. In Lua, expressions like {key = val}[key] are invalid syntax, requiring parentheses: ({key = val})[key].

Changes:

• Modified printVar function in the Lua printer to wrap table constructors in parentheses before bracket indexing, making VarIndex consistent with the existing VarField behavior

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