strange results when searching docstrings by call signatures

[matthias314]

Although it appears not to be documented, one can search docstrings by call signatures. However, the results may be wrong if methods with type parameters are involved. Here is an example:

module M

export f

"doc for f"
function f end

"doc for f(x, y)"
f(x, y) = 1

"doc for f(x::T, y)"
f(x::T, y) where T = one(T)

end

using .M

Then

help?> f(1, 1)
  doc for f(x, y)
----------------------
  doc for f(x::T, y)

as expected (the docstrings for all matching signatures are displayed), but also

help?> f(1)
  doc for f(x::T, y)

which appears wrong.

A look at the entry for f in the META dictionary

julia> first(getfield(M, Docs.META))
Pair{Any, Any}(Main.M.f, Base.Docs.MultiDoc(Type[Union{}, Tuple{Any, Any}, Union{Tuple{T}, Tuple{T, Any}} where T], IdDict{Any, Any}(Union{Tuple{T}, Tuple{T, Any}} where T => Base.Docs.DocStr(svec("doc for f(x::T, y)"), doc for f(x::T, y)
, Dict{Symbol, Any}(:typesig => Union{Tuple{T}, Tuple{T, Any}} where T, :module => Main.M, :linenumber => 11, :binding => Main.M.f, :path => "REPL[1]")), Tuple{Any, Any} => Base.Docs.DocStr(svec("doc for f(x, y)"), doc for f(x, y)
, Dict{Symbol, Any}(:typesig => Tuple{Any, Any}, :module => Main.M, :linenumber => 8, :binding => Main.M.f, :path => "REPL[1]")), Union{} => Base.Docs.DocStr(svec("doc for f"), nothing, Dict{Symbol, Any}(:typesig => Union{}, :module => Main.M, :linenumber => 5, :binding => Main.M.f, :path => "REPL[1]")))))

shows that the call signatures Union{}, Tuple{Any, Any} and Union{Tuple{T}, Tuple{T, Any}} where T are registered. The third one probably causes the strange result above.

I have found the following possibly related docstring in the source code:

https://github.com/JuliaLang/julia/blob/2b2f5344138f2b50ee91132592733743f33c5358/base/docs/Docs.jl#L191-L209

As far as I can tell, the example is correct. However, in the light of my example above, the reason that Tuple{T} appears in Union{Tuple{T, Any}, Tuple{T}} where T seems to be that T is a type parameter and not that f(x::T) is a valid signature. I doubt that this was not intended.

Tested on Julia 1.10.0.

[LilithHafner]

This is perhaps related:

julia> NamedTuple{(:a,), Tuple{Int}}(5)
(a = 5,)

help?> NamedTuple{(:a,), Tuple{Int}}(5)
ERROR: syntax: invalid variable expression in "where" around /cache/build/builder-armageddon-4/julialang/julia-release-1-dot-11/usr/share/julia/stdlib/v1.11/REPL/src/docview.jl:28
Stacktrace:
 [1] top-level scope
   @ none:1

[matthias314]

Yes, that's related. It would be fixed by #53824. I didn't check #54324, but I assume it would fix it, too.

[thofma]

Is this a duplicate of https://github.com/JuliaLang/julia/issues/29437? (Edit: It is)