From 83d90f146398bf6cff751d239406328dbb95e724 Mon Sep 17 00:00:00 2001
From: gingerBill <bill@gingerbill.org>
Date: Sun, 28 Jan 2018 09:51:52 +0000
Subject: [PATCH] Extra check for `type_info` cycle checking

---
 src/check_expr.cpp | 35 ++++++++++++++++++++++++++---------
 src/check_type.cpp |  4 ++++
 src/checker.hpp    |  1 +
 3 files changed, 31 insertions(+), 9 deletions(-)

diff --git a/src/check_expr.cpp b/src/check_expr.cpp
index 2725447c4..9b25f2655 100644
--- a/src/check_expr.cpp
+++ b/src/check_expr.cpp
@@ -3242,23 +3242,40 @@ bool check_builtin_procedure(Checker *c, Operand *operand, AstNode *call, i32 id
 	}
 
 
-	case BuiltinProc_type_of:
+	case BuiltinProc_type_of: {
 		// proc type_of(val: Type) -> type(Type)
-		check_assignment(c, operand, nullptr, str_lit("argument of 'type_of'"));
-		if (operand->mode == Addressing_Invalid || operand->mode == Addressing_Builtin) {
+		AstNode *expr = ce->args[0];
+		Operand o = {};
+		check_expr_or_type(c, &o, expr);
+
+		// check_assignment(c, operand, nullptr, str_lit("argument of 'type_of'"));
+		if (o.mode == Addressing_Invalid || o.mode == Addressing_Builtin) {
 			return false;
 		}
-		if (operand->type == nullptr || operand->type == t_invalid) {
-			error(operand->expr, "Invalid argument to 'type_of'");
+		if (o.type == nullptr || o.type == t_invalid) {
+			error(o.expr, "Invalid argument to 'type_of'");
 			return false;
 		}
-		if (is_type_polymorphic(operand->type)) {
-			error(operand->expr, "'type_of' of polymorphic type cannot be determined");
+		if (o.type == nullptr || o.type == t_invalid) {
+			error(o.expr, "Invalid argument to 'type_of'");
+			return false;
+		}
+		// NOTE(bill): Prevent type cycles for procedure declarations
+		if (c->context.curr_proc_sig == o.type) {
+			gbString s = expr_to_string(o.expr);
+			error(o.expr, "Invalid cyclic type usage from 'type_of', got '%s'", s);
+			gb_string_free(s);
+			return false;
+		}
+
+		if (is_type_polymorphic(o.type)) {
+			error(o.expr, "'type_of' of polymorphic type cannot be determined");
 			return false;
 		}
 		operand->mode = Addressing_Type;
+		operand->type = o.type;
 		break;
-
+	}
 
 	case BuiltinProc_type_info_of: {
 		// proc type_info_of(Type) -> ^Type_Info
@@ -3270,7 +3287,7 @@ bool check_builtin_procedure(Checker *c, Operand *operand, AstNode *call, i32 id
 		init_preload(c);
 		AstNode *expr = ce->args[0];
 		Operand o = {};
-		check_expr_or_type(c, &o, ce->args[0]);
+		check_expr_or_type(c, &o, expr);
 		if (o.mode == Addressing_Invalid) {
 			return false;
 		}
diff --git a/src/check_type.cpp b/src/check_type.cpp
index 41c975185..4beb88bdb 100644
--- a/src/check_type.cpp
+++ b/src/check_type.cpp
@@ -1671,6 +1671,10 @@ bool check_procedure_type(Checker *c, Type *type, AstNode *proc_type_node, Array
 		c->context.polymorphic_scope = c->context.scope;
 	}
 
+	CheckerContext prev = c->context;
+	defer (c->context = prev);
+	c->context.curr_proc_sig = type;
+
 	bool variadic = false;
 	isize variadic_index = -1;
 	bool success = true;
diff --git a/src/checker.hpp b/src/checker.hpp
index f3507d2d5..29b8eae1a 100644
--- a/src/checker.hpp
+++ b/src/checker.hpp
@@ -275,6 +275,7 @@ struct CheckerContext {
 	String     proc_name;
 	Type *     type_hint;
 	DeclInfo * curr_proc_decl;
+	Type *     curr_proc_sig;
 	ForeignContext foreign_context;
 
 	bool       collect_delayed_decls;