Resolve embedded-interface fields in get() builtin (match member access)#977
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greymoth-jp wants to merge 1 commit into
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Resolve embedded-interface fields in get() builtin (match member access)#977greymoth-jp wants to merge 1 commit into
greymoth-jp wants to merge 1 commit into
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runtime.Fetch was taught in expr-lang#952 to resolve a field on the concrete type held by an embedded interface, but the sibling builtin get() was left on the old standard-promotion-only lookup. get() is documented to differ from runtime.Fetch only in returning nil instead of panicking, so the same field access returned a value through member access (a.field) yet nil through get(a, "field"). Share the traversal by exporting runtime.FetchFromEmbeddedInterfaces and calling it from get()'s struct branch, mirroring Fetch. Adds a regression test under test/issues/952.
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The builtin
get(obj, "field")doesn't resolve fields on the concrete type behind an embedded interface, while member access(...).fielddoes. So for a value whose static type is unknown at compile time,(cond ? x : y).Valuereturns the value butget((cond ? x : y), "Value")returns nil — inconsistent access for the same field.PR #952 added
fetchFromEmbeddedInterfacestoruntime.Fetchbut left its siblingget()behind; #935 had previously kept the two in lockstep. The fix mirrors #952's logic intoget().Verified both ways with
go test: old returns nil, fixed returns the value; a missing field still returns nil (no panic), zero regression across the suite.