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Update showarg docstring #58509

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81dba65
Update showarg docstring
LilithHafner May 23, 2025
0674b03
Split sentance
LilithHafner May 23, 2025
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32 changes: 19 additions & 13 deletions base/show.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -3222,17 +3222,23 @@ end
summary(io::IO, f::Function) = show(io, MIME"text/plain"(), f)

"""
showarg(io::IO, x, toplevel)
Base.showarg(io::IO, x, toplevel)

Show `x` as if it were an argument to a function. This function is
used by [`summary`](@ref) to display type information in terms of sequences of
function calls on objects. `toplevel` is `true` if this is
the direct call from `summary` and `false` for nested (recursive) calls.
Show the quasi-type of `x` where quasi-type is the type of `x` or an expression (possibly
containing quasi-types) that would generate an object of the same type as `x`, whichever is
shorter.

The fallback definition is to print `x` as "::\\\$(typeof(x))",
representing argument `x` in terms of its type. (The double-colon is
omitted if `toplevel=true`.) However, you can
specialize this function for specific types to customize printing.
This function is used by summary to display type information in terms of sequences of
function calls on objects.

Show a leading `::` if `toplevel` is `false` and showing a type. `toplevel` is `true` if
this is the direct call from `summary` and `false` for nested (recursive) calls.

The fallback definition is to print x as "::$(typeof(x))", representing argument x in terms
of its type. (The double-colon is omitted if toplevel=true.) However, you can specialize
this function for specific types to customize printing. This customization is useful for
types that have simple constructors and verbose types such as `reinterpret`ed arrays or
`SubArray`s.

# Examples

Expand Down Expand Up @@ -3261,14 +3267,14 @@ type, indicating that any recursed calls are not at the top level.
Printing the parent as `::Array{Float64,3}` is the fallback (non-toplevel)
behavior, because no specialized method for `Array` has been defined.
"""
function showarg(io::IO, T::Type, toplevel)
toplevel || print(io, "::")
print(io, "Type{", T, "}")
end
function showarg(io::IO, @nospecialize(x), toplevel)
toplevel || print(io, "::")
print(io, typeof(x))
end
function showarg(io::IO, T::Type, toplevel)
toplevel || print(io, "::")
print(io, "Type{", T, "}")
end
# This method resolves an ambiguity for packages that specialize on eltype
function showarg(io::IO, a::Array{Union{}}, toplevel)
toplevel || print(io, "::")
Expand Down