Limit indexing to AbstractArray

NEWS.md

@@ -82,7 +82,7 @@ New library features
 
 * The `redirect_*` functions can now be called on `IOContext` objects.
 * New constructor `NamedTuple(iterator)` that constructs a named tuple from a key-value pair iterator.
-* Generators support `getindex`, `firstindex`, and `lastindex` if indexing is supported by the underlying iterator ([#37648]).
+* Generators support `getindex` when the underlying iterator is a subtype of `AbstractArray` ([#37648]).
 
 Standard library changes
 ------------------------

base/generator.jl

@@ -62,8 +62,6 @@ function getindex(g::Generator{<:AbstractArray}, I...)
     end
 end
 
-getindex(g::Generator, I...) = collect(g)[I...]
-
 firstindex(g::Generator) = firstindex(g.iter)
 lastindex(g::Generator) = lastindex(g.iter)
 

test/functional.jl

@@ -230,5 +230,5 @@ end
 
     @test (tuple(x) for x in ["a"])[1] == ("a",)
     @test (tuple(x) for x in [[0]])[1] == ([0],)
-    @test (x * y for (x, y) in Dict(3 => 4))[1] == 12
+    @test_throws MethodError (x * y for (x, y) in Dict(3 => 4))[1]
 end