Don't error on help for keyword functions (#29308)

Fixes #23991.

Also allows for help where some arguments are undefined.

stdlib/REPL/src/docview.jl

@@ -294,8 +294,56 @@ repl(io::IO, other) = esc(:(@doc $other))
 repl(x) = repl(stdout, x)
 
 function _repl(x)
-    if (isexpr(x, :call) && !any(isexpr(x, :(::)) for x in x.args))
-        x.args[2:end] = [:(::typeof($arg)) for arg in x.args[2:end]]
+    if isexpr(x, :call)
+        # determine the types of the values
+        kwargs = nothing
+        pargs = Any[]
+        for arg in x.args[2:end]
+            if isexpr(arg, :parameters)
+                kwargs = map(arg.args) do kwarg
+                    if kwarg isa Symbol
+                        kwarg = :($kwarg::Any)
+                    elseif isexpr(kwarg, :kw)
+                        lhs = kwarg.args[1]
+                        rhs = kwarg.args[2]
+                        if lhs isa Symbol
+                            if rhs isa Symbol
+                                kwarg.args[1] = :($lhs::(@isdefined($rhs) ? typeof($rhs) : Any))
+                            else
+                                kwarg.args[1] = :($lhs::typeof($rhs))
+                            end
+                        end
+                    end
+                    kwarg
+                end
+            elseif isexpr(arg, :kw)
+                if kwargs == nothing
+                    kwargs = Any[]
+                end
+                lhs = arg.args[1]
+                rhs = arg.args[2]
+                if lhs isa Symbol
+                    if rhs isa Symbol
+                        arg.args[1] = :($lhs::(@isdefined($rhs) ? typeof($rhs) : Any))
+                    else
+                        arg.args[1] = :($lhs::typeof($rhs))
+                    end
+                end
+                push!(kwargs, arg)
+            else
+                if arg isa Symbol
+                    arg = :($arg::(@isdefined($arg) ? typeof($arg) : Any))
+                elseif !isexpr(arg, :(::))
+                    arg = :(::typeof($arg))
+                end
+                push!(pargs, arg)
+            end
+        end
+        if kwargs == nothing
+            x.args = Any[x.args[1], pargs...]
+        else
+            x.args = Any[x.args[1], Expr(:parameters, kwargs...), pargs...]
+        end
     end
     #docs = lookup_doc(x) # TODO
     docs = esc(:(@doc $x))

test/docs.jl

@@ -992,6 +992,20 @@ let dt2 = _repl(:(dynamic_test(::String)))
     @test dt2.args[1].args[1] == Symbol("@doc")
     @test dt2.args[1].args[3] == :(dynamic_test(::String))
 end
+let dt3 = _repl(:(dynamic_test(a)))
+    @test dt3 isa Expr
+    @test dt3.args[1] isa Expr
+    @test dt3.args[1].head === :macrocall
+    @test dt3.args[1].args[1] == Symbol("@doc")
+    @test dt3.args[1].args[3].args[2].head == :(::) # can't test equality due to line numbers
+end
+let dt4 = _repl(:(dynamic_test(1.0,u=2.0)))
+    @test dt4 isa Expr
+    @test dt4.args[1] isa Expr
+    @test dt4.args[1].head === :macrocall
+    @test dt4.args[1].args[1] == Symbol("@doc")
+    @test dt4.args[1].args[3] == :(dynamic_test(::typeof(1.0); u::typeof(2.0)=2.0))
+end
 
 # Equality testing