Added tests for typechecking

tests_ispcpp/error_0.ispc

@@ -0,0 +1,6 @@
+//@error
+//assigning mismatched polymorphic types
+
+export void foo(floating<0> bar) {
+    floating<1> baz = bar;
+}

tests_ispcpp/error_1.ispc

@@ -0,0 +1,6 @@
+//@error
+//assigning mismatched polymorphic types
+
+export void foo(floating<0> bar) {
+    floating baz = bar;
+}

tests_ispcpp/error_2.ispc

@@ -0,0 +1,6 @@
+//@error
+//assigning mismatched polymorphic types
+
+export void foo(number<0> bar) {
+    floating<0> baz = bar;
+}

tests_ispcpp/error_3.ispc

@@ -0,0 +1,6 @@
+//@error
+//assigning mismatched polymorphic types
+
+export void foo(number<0> bar) {
+    integer baz = bar;
+}

tests_ispcpp/error_4.ispc

@@ -0,0 +1,19 @@
+//@error
+// cannot determine return type for mult
+
+
+floating mult(floating<0> x, floating<1>y) {
+    return x * y;
+}
+
+export void saxpy(uniform int N,
+                  uniform floating<0> scale,
+                  uniform floating<1> X[],
+                  uniform floating<1> Y[],
+                  uniform floating<2> result[])
+{
+    foreach (i = 0 ... N) {
+        floating<2> tmp = mult(scale, X[i]) + Y[i];
+        result[i] = tmp;
+    }
+}