go/format: printer omits parens around type in T(x) in synthetic AST #63362
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Change https://go.dev/cl/532556 mentions this issue: |
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Change https://go.dev/cl/532576 mentions this issue: |
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This change adds parens around the type in T(x) conversions where T is a receive-only channel type, as previously it would be misformatted as a receive of a receive. Updates golang/go#63362 Change-Id: I935b5598d4bc3ea57dd52964e8b02005f5e6ef72 Reviewed-on: https://go-review.googlesource.com/c/tools/+/532576 Reviewed-by: Robert Findley <[email protected]> LUCI-TryBot-Result: Go LUCI <[email protected]>
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https://go.dev/play/p/p5A4mFaqogQ creates a synthetic syntax tree representing
<-(<-chan int)(nil). The go/format printer renders this as<-<-chan int(nil), which parses to a different tree--a receive of a receive--that doesn't type check because the channel value is int. (If instead we had used<-<-chan chan int(nil), the result would type check but would have a different meaning.) The parser creates a ParenExpr around the type so the problem doesn't show up in gofmt, but only in refactoring tools that create syntax trees programmatically.I think this is a bug in the printer, and that it should emit parens.
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