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adonovan opened this issue Oct 2, 2023 · 1 comment
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x/tools/internal/refactor/inline: more precise analysis of return conversions in tail-call strategy #63336

adonovan opened this issue Oct 2, 2023 · 1 comment
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FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done. Tools This label describes issues relating to any tools in the x/tools repository.
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@adonovan
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adonovan commented Oct 2, 2023

This call in callee.go:

				argType := func(i int) types.Type {
					return info.TypeOf(n.Results[i]) // inline
				}

is inlined to

				argType := func(i int) types.Type {
					return func(e ast.Expr) types.Type {
						if t, ok := info.Types[e]; ok {
							return t.Type
						}
						if id, _ := e.(*ast.Ident); id != nil {
							if obj := info.ObjectOf(id); obj != nil {
								return obj.Type()
							}
						}
						return nil
					}(n.Results[i])
				}

I think the only reason is that the final return nil involves a non-trivial conversion from untyped nil to Type(nil), yet TypeOf() is being tailcalled in a Type context, so it's quite safe. It would be nice if this were reduced to this:

				argType := func(i int) types.Type {
					var e ast.Expr = n.Results[i]
					if t, ok := info.Types[e]; ok {
						return t.Type
					}
					if id, _ := e.(*ast.Ident); id != nil {
						if obj := info.ObjectOf(id); obj != nil {
							return obj.Type()
						}
					}
					return nil
				}

(This is a feature request for a [style] optimization, not a bug, in the terms of source-level inliner.)
@gopherbot gopherbot added the Tools This label describes issues relating to any tools in the x/tools repository. label Oct 2, 2023
@gopherbot gopherbot added this to the Unreleased milestone Oct 2, 2023
@prattmic prattmic added the NeedsFix The path to resolution is known, but the work has not been done. label Oct 3, 2023
@adonovan adonovan self-assigned this Oct 5, 2023
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Change https://go.dev/cl/533075 mentions this issue: internal/refactor/inline: permit return conversions in tailcall

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