From 424e2deb24f2643280535eb6b93a9211f1634973 Mon Sep 17 00:00:00 2001
From: Jason LaPorte <ironwallaby@gmail.com>
Date: Tue, 30 Jul 2013 13:50:36 -0400
Subject: [PATCH] Added some addition type-safety checks.

---
 lib/template.js | 16 ++++++++++++----
 test.js         |  8 ++++++++
 2 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/lib/template.js b/lib/template.js
index 0d590921..76be0dbe 100644
--- a/lib/template.js
+++ b/lib/template.js
@@ -38,10 +38,18 @@ module.exports = function(template) {
           return parse(expr[n.slice(1)|0]);
         });
 
-      else if(typeof template[expr[0]] === "function")
-        return template[expr[0]].apply(null, expr.slice(1).map(function(arg) {
-          return parse(arg);
-        }));
+      else if(typeof template[expr[0]] === "function") {
+        if(template[expr[0]].length === 0)
+          throw new Error("\"" + expr[0] + "\" was used in a template context, but is expected in a value context.");
+
+        else if(template[expr[0]].length !== expr.length - 1)
+          throw new Error("Template \"" + expr[0] + "\" did not expect " + (expr.length - 1) + " arguments.");
+
+        else
+          return template[expr[0]].apply(null, expr.slice(1).map(function(arg) {
+            return parse(arg);
+          }));
+      }
 
       else
         throw new Error("\"" + expr[0] + "\" is not a valid language template pattern.");
diff --git a/test.js b/test.js
index 48fec5f3..2cf5e90f 100644
--- a/test.js
+++ b/test.js
@@ -42,6 +42,10 @@ describe("translation", function() {
       expect(convert(["bar", 10, 20])).to.equal("meeple 20");
     });
 
+    it("should fail to apply a function template given the wrong number of arguments", function() {
+      expect(function() { convert(["baz", 10, 20, 30]); }).to.throw();
+    });
+
     it("should apply a function template", function() {
       expect(convert(["baz", 10, 20])).to.equal("meeple 20");
     });
@@ -68,6 +72,10 @@ describe("translation", function() {
       expect(convert("quux")).to.equal("glorple");
     });
 
+    it("should fail to apply a zero-argument function given arguments", function() {
+      expect(function() { convert(["quux"]); }).to.throw();
+    });
+
     it("should fail to apply a function template given a value", function() {
       expect(function() { convert("baz"); }).to.throw();
     });