Allow builder DSL to accept implicit arrays and hashes

[chrisandreae]

When a builder DSL method is called with multiple arguments (including the block argument), or keyword arguments, construct the attribute as an array or hash respectively.

[thefloweringash]

I'm looking for an argument for which cases should be accepted with implicit wrapping and which should be rejected. For the positional+block case the positional argument implicitly gets wrapped in an array, which is to say the overall type is changed to accommodate the block. Should this also apply to maps derived from keyword arguments?

For example:

# Current behavior (IIUC)
x(1)            => 1
x(1) { }        => [1, ->(){}]

# Do these seem consistent?
x(x: :y)                  => { :x => :y }
x(x: :y) {}               => [{ :x => :y }, ->(){}]
x(1, x: :y) { }           => [1, { :x => :y }, ->(){}]
x(1, 2, x: :y, p: :q) { } => [1, 2, { :x => :y, :p => :q }, ->(){}]