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require_relative '../spec_helper'
ruby_version_is "2.7" do
describe "Numbered parameters" do
it "provides default parameters _1, _2, ... in a block" do
-> { _1 }.call("a").should == "a"
proc { _1 }.call("a").should == "a"
lambda { _1 }.call("a").should == "a"
["a"].map { _1 }.should == ["a"]
end
it "assigns nil to not passed parameters" do
proc { [_1, _2] }.call("a").should == ["a", nil]
proc { [_1, _2] }.call("a", "b").should == ["a", "b"]
end
it "supports variables _1-_9 only for the first 9 passed parameters" do
block = proc { [_1, _2, _3, _4, _5, _6, _7, _8, _9] }
result = block.call(1, 2, 3, 4, 5, 6, 7, 8, 9)
result.should == [1, 2, 3, 4, 5, 6, 7, 8, 9]
end
it "does not support more than 9 parameters" do
-> {
proc { [_10] }.call(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
}.should raise_error(NameError, /undefined local variable or method `_10'/)
end
it "can not be used in both outer and nested blocks at the same time" do
-> {
eval("-> { _1; -> { _2 } }")
}.should raise_error(SyntaxError, /numbered parameter is already used in/m)
end
ruby_version_is '2.7'...'3.0' do
it "can be overwritten with local variable" do
suppress_warning do
eval <<~CODE
_1 = 0
proc { _1 }.call("a").should == 0
CODE
end
end
it "warns when numbered parameter is overwritten with local variable" do
-> {
eval("_1 = 0")
}.should complain(/warning: `_1' is reserved for numbered parameter; consider another name/)
end
end
ruby_version_is '3.0' do
it "cannot be overwritten with local variable" do
-> {
eval <<~CODE
_1 = 0
proc { _1 }.call("a").should == 0
CODE
}.should raise_error(SyntaxError, /_1 is reserved for numbered parameter/)
end
it "errors when numbered parameter is overwritten with local variable" do
-> {
eval("_1 = 0")
}.should raise_error(SyntaxError, /_1 is reserved for numbered parameter/)
end
end
it "raises SyntaxError when block parameters are specified explicitly" do
-> { eval("-> () { _1 }") }.should raise_error(SyntaxError, /ordinary parameter is defined/)
-> { eval("-> (x) { _1 }") }.should raise_error(SyntaxError, /ordinary parameter is defined/)
-> { eval("proc { || _1 }") }.should raise_error(SyntaxError, /ordinary parameter is defined/)
-> { eval("proc { |x| _1 }") }.should raise_error(SyntaxError, /ordinary parameter is defined/)
-> { eval("lambda { || _1 }") }.should raise_error(SyntaxError, /ordinary parameter is defined/)
-> { eval("lambda { |x| _1 }") }.should raise_error(SyntaxError, /ordinary parameter is defined/)
-> { eval("['a'].map { || _1 }") }.should raise_error(SyntaxError, /ordinary parameter is defined/)
-> { eval("['a'].map { |x| _1 }") }.should raise_error(SyntaxError, /ordinary parameter is defined/)
end
it "affects block arity" do
-> { _1 }.arity.should == 1
-> { _2 }.arity.should == 2
-> { _3 }.arity.should == 3
-> { _4 }.arity.should == 4
-> { _5 }.arity.should == 5
-> { _6 }.arity.should == 6
-> { _7 }.arity.should == 7
-> { _8 }.arity.should == 8
-> { _9 }.arity.should == 9
-> { _9 }.arity.should == 9
proc { _9 }.arity.should == 9
lambda { _9 }.arity.should == 9
end
it "does not work in methods" do
obj = Object.new
def obj.foo; _1 end
-> { obj.foo("a") }.should raise_error(ArgumentError, /wrong number of arguments/)
end
end
end
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