Idempotence & version bounds tweak #159
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It's possible for the compiler plugin to fire multiple times, with each successive run using the AST from the previous run. When this happens, the first run succeeds but later runs fail. The datatype definition generated by `transformDecl` still has the `largeRecord` annotation, but is no longer in a form that's accepted by the compiler plugin. Removing the annotations for which `transformDecl` succeeds makes the compiler plugin idempotent.
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large-recordshas been really helpful. We have a fairly bigbeamschema, and when combined withbeam-automigratecompilation ran out of memory on an 8GB system. With alarge-recordsschema, the peak memory usage during compilation is ~2.5GB.Plugin idempotence
When I used
large-recordsin GHCi1 I found that the plugin fired twice, feeding the output from the first run into the second run. I got an error, because the output of the first run is an invalidlarge-recordsdeclaration. This change removes the annotation when thelarge-recordsdeclaration is processed, so that subsequent runs don't try to transform already-transformed datatypes.primitiveversion boundsWe're stuck with an older version of
primitive, andlarge-recordsseems to work with it.Footnotes
We're using Obelisk to launch GHCi. I noticed that Obelisk uses a syntax preprocessor (
-pgmF); I wonder if that has something to do with it. ↩