Support all iterators again

Author: omus

NEWS.md

@@ -92,7 +92,7 @@ New library features
 * New constructor `NamedTuple(iterator)` that constructs a named tuple from a key-value pair iterator.
 * A new `reinterpret(reshape, T, a::AbstractArray{S})` reinterprets `a` to have eltype `T` while potentially
   inserting or consuming the first dimension depending on the ratio of `sizeof(T)` and `sizeof(S)`.
-* Generators support `getindex` when the underlying iterator is a subtype of `AbstractArray` ([#37648]).
+* Generators support `getindex`, `firstindex`, and `lastindex` ([#37648]).
 
 Standard library changes
 ------------------------

base/generator.jl

@@ -62,6 +62,16 @@ function getindex(g::Generator{<:AbstractArray}, I...)
     end
 end
 
+function getindex(g::Generator, I...)
+    A = collect(g.iter)
+    subset = A[I...]
+    if typeof(subset) == eltype(A)
+        g.f(subset)
+    else
+        map(g.f, subset)
+    end
+end
+
 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_throws MethodError (x * y for (x, y) in Dict(3 => 4))[1]
+    @test (x * y for (x, y) in Dict(3 => 4))[1] == 12
 end