4 files changed, 61 insertions, 59 deletions

diff --git a/examples/core.zig b/examples/core.zig
index 8bcc928..eb512ef 100644
--- a/examples/core.zig
+++ b/examples/core.zig
@@ -7,8 +7,10 @@ const mem = std.mem;
 const Names = clap.Names;
 const Param = clap.Param;
 
+const ArgError = clap.OsArgIterator.Error;
+
 // TODO: More specific error in this func type.
-const Command = fn(&mem.Allocator, &clap.ArgIterator) error!void;
+const Command = fn(&mem.Allocator, &clap.ArgIterator(ArgError)) error!void;
 
 const params = []Param(Command){
     Param(Command).init(help, false, Names.prefix("help")),
@@ -52,11 +54,12 @@ pub fn main() !void {
 
     const allocator = &arena.allocator;
 
-    var args = clap.OsArgIterator.init();
-    var parser = clap.Clap(Command).init(params, &args.iter, allocator);
-    defer parser.deinit();
+    var args = clap.OsArgIterator.init(allocator);
+    defer args.deinit();
+
+    const exe = try args.iter.next();
+    var parser = clap.Clap(Command, ArgError).init(params, &args.iter);
 
-    const exe = try parser.nextNoParse();
     const maybe_arg = parser.next() catch |err| b: {
         debug.warn("{}.\n", @errorName(err));
         // debug.warn(usage); TODO: error: evaluation exceeded 1000 backwards branches
@@ -71,7 +74,7 @@ pub fn main() !void {
     try arg.param.id(allocator, parser.iter);
 }
 
-pub fn help(allocator: &mem.Allocator, args: &clap.ArgIterator) (error{}!void) {
+pub fn help(allocator: &mem.Allocator, args: &clap.ArgIterator(ArgError)) (error{}!void) {
     // debug.warn(usage); TODO: error: evaluation exceeded 1000 backwards branches
 }
 
@@ -144,7 +147,7 @@ const missing_build_file =
     \\
 ;
 
-fn cmdBuild(allocator: &mem.Allocator, args: &clap.ArgIterator) !void {
+fn cmdBuild(allocator: &mem.Allocator, args: &clap.ArgIterator(ArgError)) !void {
     var init = false;
     var build_file: []const u8 = "build.zig";
     var cache_dir: []const u8 = "zig-cache";
@@ -157,8 +160,7 @@ fn cmdBuild(allocator: &mem.Allocator, args: &clap.ArgIterator) !void {
     var verbose_llvm_ir = false;
     var verbose_cimport = false;
 
-    var parser = clap.Clap(Build).init(build_params, args, allocator);
-    defer parser.deinit();
+    var parser = clap.Clap(Build, ArgError).init(build_params, args);
 
     while (parser.next() catch |err| {
         debug.warn("{}.\n", @errorName(err));
@@ -321,17 +323,17 @@ const build_generic_usage =
 ;
 
 
-fn cmdBuildExe(allocator: &mem.Allocator, args: &clap.ArgIterator) (error{}!void) {
+fn cmdBuildExe(allocator: &mem.Allocator, args: &clap.ArgIterator(ArgError)) (error{}!void) {
 }
 
 // cmd:build-lib ///////////////////////////////////////////////////////////////////////////////////
 
-fn cmdBuildLib(allocator: &mem.Allocator, args: &clap.ArgIterator) (error{}!void) {
+fn cmdBuildLib(allocator: &mem.Allocator, args: &clap.ArgIterator(ArgError)) (error{}!void) {
 }
 
 // cmd:build-obj ///////////////////////////////////////////////////////////////////////////////////
 
-fn cmdBuildObj(allocator: &mem.Allocator, args: &clap.ArgIterator) (error{}!void) {
+fn cmdBuildObj(allocator: &mem.Allocator, args: &clap.ArgIterator(ArgError)) (error{}!void) {
 }
 
 // cmd:fmt /////////////////////////////////////////////////////////////////////////////////////////
@@ -348,17 +350,17 @@ const usage_fmt =
     \\
 ;
 
-fn cmdFmt(allocator: &mem.Allocator, args: &clap.ArgIterator) (error{}!void) {
+fn cmdFmt(allocator: &mem.Allocator, args: &clap.ArgIterator(ArgError)) (error{}!void) {
 }
 
 // cmd:targets /////////////////////////////////////////////////////////////////////////////////////
 
-fn cmdTargets(allocator: &mem.Allocator, args: &clap.ArgIterator) (error{}!void) {
+fn cmdTargets(allocator: &mem.Allocator, args: &clap.ArgIterator(ArgError)) (error{}!void) {
 }
 
 // cmd:version /////////////////////////////////////////////////////////////////////////////////////
 
-fn cmdVersion(allocator: &mem.Allocator, args: &clap.ArgIterator) (error{}!void) {
+fn cmdVersion(allocator: &mem.Allocator, args: &clap.ArgIterator(ArgError)) (error{}!void) {
 }
 
 // cmd:test ////////////////////////////////////////////////////////////////////////////////////////
@@ -372,7 +374,7 @@ const usage_test =
     \\
 ;
 
-fn cmdTest(allocator: &mem.Allocator, args: &clap.ArgIterator) (error{}!void) {
+fn cmdTest(allocator: &mem.Allocator, args: &clap.ArgIterator(ArgError)) (error{}!void) {
 }
 
 // cmd:run /////////////////////////////////////////////////////////////////////////////////////////
@@ -388,7 +390,7 @@ const usage_run =
     \\
 ;
 
-fn cmdRun(allocator: &mem.Allocator, args: &clap.ArgIterator) (error{}!void) {
+fn cmdRun(allocator: &mem.Allocator, args: &clap.ArgIterator(ArgError)) (error{}!void) {
 }
 
 // cmd:translate-c /////////////////////////////////////////////////////////////////////////////////
@@ -404,7 +406,7 @@ const usage_translate_c =
     \\
 ;
 
-fn cmdTranslateC(allocator: &mem.Allocator, args: &clap.ArgIterator) (error{}!void) {
+fn cmdTranslateC(allocator: &mem.Allocator, args: &clap.ArgIterator(ArgError)) (error{}!void) {
 }
 
 // cmd:zen /////////////////////////////////////////////////////////////////////////////////////////
@@ -426,7 +428,7 @@ const info_zen =
     \\
 ;
 
-fn cmdZen(allocator: &mem.Allocator, args: &clap.ArgIterator) (error{}!void) {
+fn cmdZen(allocator: &mem.Allocator, args: &clap.ArgIterator(ArgError)) (error{}!void) {
 }
 
 // cmd:internal ////////////////////////////////////////////////////////////////////////////////////
@@ -440,5 +442,5 @@ const usage_internal =
     \\
 ;
 
-fn cmdInternal(allocator: &mem.Allocator, args: &clap.ArgIterator) (error{}!void) {
+fn cmdInternal(allocator: &mem.Allocator, args: &clap.ArgIterator(ArgError)) (error{}!void) {
 }
diff --git a/src/core.zig b/src/core.zig
index 8570220..5e47714 100644
--- a/src/core.zig
+++ b/src/core.zig
@@ -136,34 +136,39 @@ pub fn Arg(comptime Id: type) type {
 }
 
 /// A interface for iterating over command line arguments
-pub const ArgIterator = struct {
-    const Error = error{OutOfMemory};
+pub fn ArgIterator(comptime E: type) type {
+    return struct {
+        const Self = this;
+        const Error = E;
 
-    nextFn: fn(iter: &ArgIterator, allocator: &mem.Allocator) Error!?[]const u8,
+        nextFn: fn(iter: &Self) Error!?[]const u8,
 
-    pub fn next(iter: &ArgIterator, allocator: &mem.Allocator) Error!?[]const u8 {
-        return iter.nextFn(iter, allocator);
-    }
-};
+        pub fn next(iter: &Self) Error!?[]const u8 {
+            return iter.nextFn(iter);
+        }
+    };
+}
 
 /// An ::ArgIterator, which iterates over a slice of arguments.
 /// This implementation does not allocate.
 pub const ArgSliceIterator = struct {
+    const Error = error{};
+
     args: []const []const u8,
     index: usize,
-    iter: ArgIterator,
+    iter: ArgIterator(Error),
 
     pub fn init(args: []const []const u8) ArgSliceIterator {
         return ArgSliceIterator {
             .args = args,
             .index = 0,
-            .iter = ArgIterator {
+            .iter = ArgIterator(Error) {
                 .nextFn = nextFn,
             },
         };
     }
 
-    fn nextFn(iter: &ArgIterator, allocator: &mem.Allocator) ArgIterator.Error!?[]const u8 {
+    fn nextFn(iter: &ArgIterator(Error)) Error!?[]const u8 {
         const self = @fieldParentPtr(ArgSliceIterator, "iter", iter);
         if (self.args.len <= self.index)
             return null;
@@ -176,22 +181,30 @@ pub const ArgSliceIterator = struct {
 /// An ::ArgIterator, which wraps the ArgIterator in ::std.
 /// On windows, this iterator allocates.
 pub const OsArgIterator = struct {
+    const Error = os.ArgIterator.NextError;
+
+    arena: heap.ArenaAllocator,
     args: os.ArgIterator,
-    iter: ArgIterator,
+    iter: ArgIterator(Error),
 
-    pub fn init() OsArgIterator {
+    pub fn init(allocator: &mem.Allocator) OsArgIterator {
         return OsArgIterator {
+            .arena = heap.ArenaAllocator.init(allocator),
             .args = os.args(),
-            .iter = ArgIterator {
+            .iter = ArgIterator(Error) {
                 .nextFn = nextFn,
             },
         };
     }
 
-    fn nextFn(iter: &ArgIterator, allocator: &mem.Allocator) ArgIterator.Error!?[]const u8 {
+    pub fn deinit(iter: &OsArgIterator) void {
+        iter.arena.deinit();
+    }
+
+    fn nextFn(iter: &ArgIterator(Error)) Error!?[]const u8 {
         const self = @fieldParentPtr(OsArgIterator, "iter", iter);
         if (builtin.os == builtin.Os.windows) {
-            return try self.args.next(allocator) ?? return null;
+            return try self.args.next(self.allocator) ?? return null;
         } else {
             return self.args.nextPosix();
         }
@@ -201,7 +214,7 @@ pub const OsArgIterator = struct {
 /// A command line argument parser which, given an ::ArgIterator, will parse arguments according
 /// to the ::params. ::Clap parses in an iterating manner, so you have to use a loop together with
 /// ::Clap.next to parse all the arguments of your program.
-pub fn Clap(comptime Id: type) type {
+pub fn Clap(comptime Id: type, comptime ArgError: type) type {
     return struct {
         const Self = this;
 
@@ -215,14 +228,12 @@ pub fn Clap(comptime Id: type) type {
             };
         };
 
-        arena: heap.ArenaAllocator,
         params: []const Param(Id),
-        iter: &ArgIterator,
+        iter: &ArgIterator(ArgError),
         state: State,
 
-        pub fn init(params: []const Param(Id), iter: &ArgIterator, allocator: &mem.Allocator) Self {
+        pub fn init(params: []const Param(Id), iter: &ArgIterator(ArgError)) Self {
             var res = Self {
-                .arena = heap.ArenaAllocator.init(allocator),
                 .params = params,
                 .iter = iter,
                 .state = State.Normal,
@@ -231,10 +242,6 @@ pub fn Clap(comptime Id: type) type {
             return res;
         }
 
-        pub fn deinit(clap: &Self) void {
-            clap.arena.deinit();
-        }
-
         /// Get the next ::Arg that matches a ::Param.
         pub fn next(clap: &Self) !?Arg(Id) {
             const ArgInfo = struct {
@@ -246,7 +253,7 @@ pub fn Clap(comptime Id: type) type {
 
             switch (clap.state) {
                 State.Normal => {
-                    const full_arg = (try clap.nextNoParse()) ?? return null;
+                    const full_arg = (try clap.iter.next()) ?? return null;
                     const arg_info = blk: {
                         var arg = full_arg;
                         var kind = ArgInfo.Kind.Bare;
@@ -294,7 +301,7 @@ pub fn Clap(comptime Id: type) type {
                                     if (maybe_value) |v|
                                         break :blk v;
 
-                                    break :blk (try clap.nextNoParse()) ?? return error.MissingValue;
+                                    break :blk (try clap.iter.next()) ?? return error.MissingValue;
                                 };
 
                                 return Arg(Id).init(param, value);
@@ -351,7 +358,7 @@ pub fn Clap(comptime Id: type) type {
                     return Arg(Id).init(param, null);
 
                 if (arg.len <= next_index) {
-                    const value = (try clap.nextNoParse()) ?? return error.MissingValue;
+                    const value = (try clap.iter.next()) ?? return error.MissingValue;
                     return Arg(Id).init(param, value);
                 }
 
@@ -364,11 +371,5 @@ pub fn Clap(comptime Id: type) type {
 
             return error.InvalidArgument;
         }
-
-        // Returns the next arg in the underlying arg iterator
-        pub fn nextNoParse(clap: &Self) !?[]const u8 {
-            clap.state = State.Normal;
-            return try clap.iter.next(&clap.arena.allocator);
-        }
     };
 }
diff --git a/src/extended.zig b/src/extended.zig
index b94f6f5..31e6455 100644
--- a/src/extended.zig
+++ b/src/extended.zig
@@ -103,13 +103,13 @@ pub const Command = struct {
         return res;
     }
 
-    pub fn parse(comptime command: &const Command, allocator: &mem.Allocator, arg_iter: &core.ArgIterator) !command.Result {
+    pub fn parse(comptime command: &const Command, allocator: &mem.Allocator, arg_iter: var) !command.Result {
         const Parent = struct {};
         var parent = Parent{};
         return command.parseHelper(&parent, allocator, arg_iter);
     }
 
-    fn parseHelper(comptime command: &const Command, parent: var, allocator: &mem.Allocator, arg_iter: &core.ArgIterator) !command.Result {
+    fn parseHelper(comptime command: &const Command, parent: var, allocator: &mem.Allocator, arg_iter: var) !command.Result {
         const Result = struct {
             parent: @typeOf(parent),
             result: command.Result,
@@ -159,11 +159,10 @@ pub const Command = struct {
         };
 
         var pos: usize = 0;
-        var iter = core.Clap(usize).init(core_params, arg_iter, allocator);
-        defer iter.deinit();
+        var clap = core.Clap(usize, @typeOf(arg_iter.*).Error).init(core_params, arg_iter);
 
         arg_loop:
-        while (try iter.next()) |arg| : (pos += 1) {
+        while (try clap.next()) |arg| : (pos += 1) {
             inline for(command.params) |param, i| {
                 comptime const field = "result." ++ param.field;
 
diff --git a/tests/core.zig b/tests/core.zig
index d4304a1..91b62fe 100644
--- a/tests/core.zig
+++ b/tests/core.zig
@@ -14,7 +14,7 @@ const Clap = core.Clap;
 
 fn testNoErr(params: []const Param(u8), args: []const []const u8, ids: []const u8, values: []const ?[]const u8) void {
     var arg_iter = ArgSliceIterator.init(args);
-    var iter = Clap(u8).init(params, &arg_iter.iter, debug.global_allocator);
+    var iter = Clap(u8, ArgSliceIterator.Error).init(params, &arg_iter.iter);
 
     var i: usize = 0;
     while (iter.next() catch unreachable) |arg| : (i += 1) {