From d9caed577477df28bc0a5b2d50ce44c77d23da56 Mon Sep 17 00:00:00 2001
From: Andrey Penechko <mrsmith33@yandex.ru>
Date: Sat, 19 Aug 2023 19:05:56 +0300
Subject: [PATCH] Implement automatic tuple expansion in function calls

---
 source/tests/passing.d        | 23 +++++++++++++++++++++++
 source/vox/fe/ast/expr/call.d | 16 ++++++++++++++++
 todo.txt                      |  2 ++
 3 files changed, 41 insertions(+)

diff --git a/source/tests/passing.d b/source/tests/passing.d
index 64281197..5d542145 100644
--- a/source/tests/passing.d
+++ b/source/tests/passing.d
@@ -6496,3 +6496,26 @@ void tester300(ref TestContext ctx) {
 	auto run1 = ctx.getFunctionPtr!(size_t, size_t, uint)("run1");
 	assert(run1(42, 10) == 42 - 10);
 }
+
+
+@TestInfo(&tester301)
+immutable test301 = q{--- test301
+	// Variadic args tuple forward into call
+	u32 run(u32 a, u32 b, u32 c) {
+		return caller(a, b, c);
+	}
+	u32 caller[Args...](Args... args) {
+		return sum(args);
+	}
+	u32 sum[Args...](Args... args) {
+		u32 res = 0;
+		#foreach(i, arg; args) {
+			res += arg;
+		}
+		return res;
+	}
+};
+void tester301(ref TestContext ctx) {
+	auto run = ctx.getFunctionPtr!(uint, uint, uint, uint)("run");
+	assert(run(100, 10, 1) == 111);
+}
diff --git a/source/vox/fe/ast/expr/call.d b/source/vox/fe/ast/expr/call.d
index 23c16913..a6b0dc3b 100644
--- a/source/vox/fe/ast/expr/call.d
+++ b/source/vox/fe/ast/expr/call.d
@@ -62,9 +62,25 @@ void name_resolve_call(CallExprNode* node, ref NameResolveState state) {
 	node.state = AstNodeState.name_resolve;
 	require_name_resolve(node.callee, state);
 	require_name_resolve(node.args, state);
+	expandTuples(node.args, state.context);
 	node.state = AstNodeState.name_resolve_done;
 }
 
+void expandTuples(ref AstNodes nodes, CompilationContext* c) {
+	uint length = nodes.length;
+	uint index;
+	while (index < length) {
+		auto node = nodes[index].get_node(c);
+		if (node.astType == AstType.decl_alias_array) {
+			auto aliasArray = node.as!AliasArrayDeclNode(c);
+			nodes.replaceAt(c.arrayArena, index, 1, aliasArray.items[]);
+			length = length - 1 + aliasArray.items.length;
+			continue;
+		}
+		++index;
+	}
+}
+
 // Get type from function declaration
 void type_check_call(ref AstIndex callIndex, CallExprNode* node, ref TypeCheckState state)
 {
diff --git a/todo.txt b/todo.txt
index 1f71d444..ccace000 100644
--- a/todo.txt
+++ b/todo.txt
@@ -33,6 +33,8 @@
 		- only simple types
 		- ifti of member functions needs to account for this parameter, because ifti is done before providing this arg
 	+ variadic template arguments (requires inference)
+	- alias tuple auto-expansion / manual expansion.
+		+ auto tuple expansion in function call
 	- a way to perform IFTI from user code (pass template args with names and runtime types and get)
 	- #parameter(#type type, string name, type default_value, #alias[] attributes)
 	- #function(string name, #type return_type, #parameter[] parameters, #alias[] attributes)