fix: for-in variables don't accept annotations

Closes #701.

spec/statement/forin_spec.lua

@@ -185,6 +185,23 @@ describe("forin", function()
    }))
 
    describe("regression tests", function()
+      it("does not accept annotations (#701)", util.check_syntax_error([[
+         for k <const>, v <const> in pairs(table as {string:any}) do
+             k = "hello"
+             print(k, v)
+         end
+      ]], {
+         -- skips one bad token at a time. Too much of a corner case to
+         -- add parser code just to produce a nicer error, the generic
+         -- message should be enough to indicate this is not supporter.
+         { y = 1, msg = "syntax error" },
+         { y = 1, msg = "syntax error" },
+         { y = 1, msg = "syntax error" },
+         { y = 1, msg = "syntax error" },
+         { y = 1, msg = "syntax error" },
+         { y = 1, msg = "syntax error" },
+      }))
+
       it("with an iterator declared as a nominal (#183)", util.check([[
          local type Iterator = function(): string
 

tl.lua

@@ -2532,7 +2532,7 @@ local function parse_forin(ps, i)
    local node = new_node(ps.tokens, i, "forin")
    i = i + 1
    node.vars = new_node(ps.tokens, i, "variable_list")
-   i, node.vars = parse_list(ps, i, node.vars, { ["in"] = true }, "sep", parse_variable_name)
+   i, node.vars = parse_list(ps, i, node.vars, { ["in"] = true }, "sep", parse_identifier)
    i = verify_tk(ps, i, "in")
    node.exps = new_node(ps.tokens, i, "expression_list")
    i = parse_list(ps, i, node.exps, { ["do"] = true }, "sep", parse_expression)

tl.tl

@@ -2382,7 +2382,7 @@ parse_argument_type_list = function(ps: ParseState, i: integer): integer, Type
    return i, list
 end
 
-local function parse_identifier(ps: ParseState, i: integer): integer, Node
+local function parse_identifier(ps: ParseState, i: integer): integer, Node, integer
    if ps.tokens[i].kind == "identifier" then
       return i + 1, new_node(ps.tokens, i, "identifier")
    end
@@ -2532,7 +2532,7 @@ local function parse_forin(ps: ParseState, i: integer): integer, Node
    local node = new_node(ps.tokens, i, "forin")
    i = i + 1
    node.vars = new_node(ps.tokens, i, "variable_list")
-   i, node.vars = parse_list(ps, i, node.vars, { ["in"] = true }, "sep", parse_variable_name)
+   i, node.vars = parse_list(ps, i, node.vars, { ["in"] = true }, "sep", parse_identifier)
    i = verify_tk(ps, i, "in")
    node.exps = new_node(ps.tokens, i, "expression_list")
    i = parse_list(ps, i, node.exps, { ["do"] = true }, "sep", parse_expression)