Replace `=` and `\in` with `in` in generators

At least we can reuse all the code from for loops pretty easily.

src/runestone.jl

@@ -457,23 +457,26 @@ end
 
 # replace `=` and `∈` with `in` in for-loops
 function for_loop_use_in(ctx::Context, node::JuliaSyntax.GreenNode)
-    if !(JuliaSyntax.kind(node) === K"for" && !is_leaf(node) && n_children(node) == 4)
+    if !(
+        (JuliaSyntax.kind(node) === K"for" && !is_leaf(node) && n_children(node) == 4) ||
+        (JuliaSyntax.kind(node) === K"generator" && n_children(node) == 3) # TODO: Unsure about 3.
+    )
         return nothing
     end
     pos = position(ctx.fmt_io) # In case a reset is needed later
     bytes = node_bytes(ctx, node)
     children = verified_children(node)
-    for_index = 1
+    for_index = findfirst(c -> JuliaSyntax.kind(c) === K"for" && is_leaf(c), children)::Int
     for_node = children[for_index]
-    # TODO: Could there be whitespace here before the K"for"?
     @assert JuliaSyntax.kind(for_node) === K"for" && JuliaSyntax.span(for_node) == 3 &&
         is_leaf(for_node) && JuliaSyntax.is_trivia(for_node)
-    accept_node!(ctx, for_node)
+    for i in 1:for_index
+        accept_node!(ctx, children[i])
+    end
     # The for loop specification node can be either K"=" or K"cartesian_iterator"
-    for_spec_index = 2
+    for_spec_index = for_index + 1
     for_spec_node = children[for_spec_index]
     @assert JuliaSyntax.kind(for_spec_node) in KSet"= cartesian_iterator"
-    pos_before = position(ctx.fmt_io)
     if JuliaSyntax.kind(for_spec_node) === K"="
         for_spec_node′ = replace_with_in(ctx, for_spec_node)
     else
@@ -485,7 +488,7 @@ function for_loop_use_in(ctx::Context, node::JuliaSyntax.GreenNode)
         seek(ctx.fmt_io, pos)
         return nothing
     end
-    @assert position(ctx.fmt_io) == pos + JuliaSyntax.span(for_node) + JuliaSyntax.span(for_spec_node′)
+    @assert position(ctx.fmt_io) == pos + mapreduce(JuliaSyntax.span, +, @view(children[1:for_index])) + JuliaSyntax.span(for_spec_node′)
     # Insert the new for spec node
     children′ = copy(children)
     children′[for_spec_index] = for_spec_node′

test/runtests.jl

@@ -226,11 +226,22 @@ end
     @test format_string("a >:  T   >:    S") == "a >: T >: S"
 end
 
-@testset "replace ∈ and = with in in for loops" begin
+@testset "replace ∈ and = with in in for loops and generators" begin
     for sp in ("", " ", "  "), op in ("∈", "=", "in")
         op == "in" && sp == "" && continue
+        # for loops
         @test format_string("for i$(sp)$(op)$(sp)I\nend") == "for i in I\nend"
         @test format_string("for i$(sp)$(op)$(sp)I, j$(sp)$(op)$(sp)J\nend") ==
             "for i in I, j in J\nend"
+        @test format_string("for i$(sp)$(op)$(sp)I, j$(sp)$(op)$(sp)J, k$(sp)$(op)$(sp)K\nend") ==
+            "for i in I, j in J, k in K\nend"
+        # for generators
+        for (l, r) in (("[", "]"), ("(", ")"))
+            @test format_string("$(l)i for i$(sp)$(op)$(sp)I$(r)") == "$(l)i for i in I$(r)"
+            @test format_string("$(l)(i, j) for i$(sp)$(op)$(sp)I, j$(sp)$(op)$(sp)J$(r)") ==
+                "$(l)(i, j) for i in I, j in J$(r)"
+            @test format_string("$(l)(i, j, k) for i$(sp)$(op)$(sp)I, j$(sp)$(op)$(sp)J, k$(sp)$(op)$(sp)K$(r)") ==
+                "$(l)(i, j, k) for i in I, j in J, k in K$(r)"
+        end
     end
 end