cmd/compile: panic message for failed assertion of generic type mentions shape type, not user type #53276
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mdempsky
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Change https://go.dev/cl/411695 mentions this issue: |
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These two tests fail with the 1.18 compiler frontend, because of incomplete dictionary support. This CL adds the tests for Unified IR, which currently handles them correctly, to make sure it doesn't repeat the same errors. Updates #53276. Updates #53328. Change-Id: I9f436495d28f2bc5707a17bd2527c86abacf91f1 Reviewed-on: https://go-review.googlesource.com/c/go/+/411695 Auto-Submit: Matthew Dempsky <mdempsky@google.com> Run-TryBot: Matthew Dempsky <mdempsky@google.com> TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: David Chase <drchase@google.com>
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Change https://go.dev/cl/413357 mentions this issue: |
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This CL adds alternate code paths for the frontend to plumb through rtypes to package ssagen, so the latter doesn't have to use reflectType (which in general will only have access to shape types). Note: This CL doesn't yet plumb through the rtypes for variables that escape to the heap. However, those rtypes are only used for calling runtime.newobject, and the status quo as of Go 1.18 is already to use shape rtypes for most runtime.newobject calls. (Longer term though, I would like to get rid of shape rtypes altogether.) Passes toolstash -cmp. Updates #53276. Change-Id: I76a281eca8300de2e701fbac89ead32f8568a5f2 Reviewed-on: https://go-review.googlesource.com/c/go/+/413357 TryBot-Result: Gopher Robot <gobot@golang.org> Run-TryBot: Matthew Dempsky <mdempsky@google.com> Reviewed-by: David Chase <drchase@google.com>
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https://go.dev/play/p/3Ru8nGnvTQY
The above program reports at run-time "panic: interface conversion: interface { T() go.shape.int_0 } is nil, not int".
I think the correct error is "panic: interface conversion: interface { T() int } is nil, not int".
The problem is the call to
s.reflectType(src)in ssagen/ssa.go. This is too late to do dictionary lookups, so we end up using the *runtime._type for the shape type, rather than the user type.We should push all the
reflectdata.TypePtr/reflectdata.TypeLinksymcalls earlier into the frontend, so they can be replaced with dictionary accesses when appropriate. Same applies toreflectdata.ITabAddrandreflectdata.ITabLSym./cc @randall77 @dr2chase @cuonglm
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