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Compiler: give proper error when trying to access instance variable of union type #7194

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Dec 17, 2018
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Compiler: give proper error when trying to access instance variable of union type #7194

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16 changes: 16 additions & 0 deletions spec/compiler/semantic/class_spec.cr
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Original file line number Diff line number Diff line change
Expand Up @@ -1075,4 +1075,20 @@ describe "Semantic: class" do
{ {{ Foo::Bar.superclass }}, {{ Foo::Baz.superclass }} }
)) { tuple_of [types["Foo"].metaclass, types["Foo"].metaclass] }
end

it "errors if reading instance var of union type (#7187)" do
assert_error %(
class Foo
@x = 1
end

class Bar
@x = 1
end

z = Foo.new || Bar.new
z.@x
),
"can't read instance variables of union types (@x of (Bar | Foo))"
end
end
4 changes: 4 additions & 0 deletions src/compiler/crystal/semantic/bindings.cr
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Expand Up @@ -557,6 +557,10 @@ module Crystal
obj_type = obj.type?
return unless obj_type

if obj_type.is_a?(UnionType)
raise "can't read instance variables of union types (#{name} of #{obj_type})"
end

var = visitor.lookup_instance_var(self, obj_type)
self.type = var.type
end
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