Implemented type checks

tests/errors/TypeMismatch.q

@@ -0,0 +1,7 @@
+main() {
+	writeToMemory(0)
+}
+
+writeToMemory(p Pointer) {
+	p[0] = 'A'
+}

tests/errors_test.go

@@ -36,6 +36,7 @@ var errs = []struct {
 	{"MissingOperand.q", errors.MissingOperand},
 	{"MissingOperand2.q", errors.MissingOperand},
 	{"VariableAlreadyExists.q", &errors.VariableAlreadyExists{Name: "x"}},
+	{"TypeMismatch.q", &errors.TypeMismatch{Expected: "Pointer", Encountered: "Int", ParameterName: "p"}},
 	{"UnknownFunction.q", &errors.UnknownFunction{Name: "unknown"}},
 	{"UnknownFunction2.q", &errors.UnknownFunction{Name: "f"}},
 	{"UnknownIdentifier.q", &errors.UnknownIdentifier{Name: "x"}},