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Decode single-item pointers, fix wide structs failing to compile - #3
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Inline loops over a struct's fields count every comptime branch they take, including escaping each key, against the enclosing function's quota. A struct with a few dozen fields ran past the default 1000 and failed to compile.
A *T is allocated and decoded in place, which is what recursive types like a status that embeds another status need. Encoding already dereferenced them.
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Two problems found while porting the twitter and canada schemas from serde-rs/json-benchmark.
Wide structs failed to compile
A struct with a few dozen fields and a
jsonFormatfailed with "evaluation exceeded 1000 backwards branches". The inline loops over a struct's fields run comptime code for every field (escaping its key, among other things), and all of it counts against the enclosing function's branch quota. twitter'sUserhas 40 fields.encodeStruct,encodeStructFieldsAfter,objectMembersandmaxKeyLennow raise the quota in proportion to the fields and their name lengths, viafieldsBranchQuota.*Tcould not be decodedEncoding already dereferenced single-item pointers, but decoding hit
@compileError. A*Tis now allocated and decoded in place. That is what recursive types need: twitter'sStatusholds aretweeted_status: ?*Status.Tests
Both cases have a test that fails without the fix: a 48-field struct with
jsonFormat, and a recursive node type plus a bare*const u32.zig build testpasses on 0.16 and 0.17.