Add more tests for property interpolation

Author: phipsgabler

src/sugar.jl

@@ -236,6 +236,11 @@ julia> t = ("one", "two")
 
 julia> set(t, (@lens _[1]), "1")
 ("1", "two")
+
+julia> # Indices are always evaluated in external scope; for properties, you can use interpolation:
+       n, i = :a, 10
+       @lens(_.\$n[i, i+1])
+(@lens _.a[10, 11])
 ```
 
 """

test/test_core.jl

@@ -510,8 +510,12 @@ end
     @test @lens(_.a ∘ $lbc) == @lens(_.a) ∘ lbc
     @test @lens(_.a ∘ $lbc ∘ _[1] ∘ $lbc) == @lens(_.a) ∘ lbc ∘ @lens(_[1]) ∘ lbc
 
+    # property interpolation
     name = :a
+    fancy(name, suffix) = Symbol("fancy_", name, suffix)
     @test @lens(_.$name) == @lens(_.a)
+    @test @lens(_.x[1, :].$name) == @lens(_.x[1, :].a)
+    @test @lens(_.x[1, :].$(fancy(name, "✨"))) == @lens(_.x[1, :].var"fancy_a✨")
 end
 
 end