Implemented register calls

tests/errors/UnknownType.q

@@ -0,0 +1,5 @@
+main() {}
+
+f(x unknown) -> int {
+	return x
+}

tests/errors/UnknownType2.q

@@ -0,0 +1,5 @@
+main() {}
+
+f(x int) -> unknown {
+	return x
+}

tests/errors/UnusedVariable2.q

@@ -0,0 +1,3 @@
+main() {}
+
+f(x int) {}

tests/errors_test.go

@@ -58,10 +58,13 @@ var errs = []struct {
 	{"UnknownIdentifier2.q", &errors.UnknownIdentifier{Name: "x"}},
 	{"UnknownIdentifier3.q", &errors.UnknownIdentifier{Name: "x"}},
 	{"UnknownPackage.q", &errors.UnknownPackage{Name: "sys"}},
+	{"UnknownType.q", &errors.UnknownType{Name: "unknown"}},
+	{"UnknownType2.q", &errors.UnknownType{Name: "unknown"}},
 	{"UnknownStructField.q", &errors.UnknownStructField{StructName: "A", FieldName: "x"}},
 	{"UntypedExpression.q", errors.UntypedExpression},
 	{"UnusedImport.q", &errors.UnusedImport{Package: "sys"}},
 	{"UnusedVariable.q", &errors.UnusedVariable{Name: "x"}},
+	{"UnusedVariable2.q", &errors.UnusedVariable{Name: "x"}},
 	{"VariableAlreadyExists.q", &errors.VariableAlreadyExists{Name: "x"}},
 }
 

tests/programs/function-pointer.q

@@ -0,0 +1,6 @@
+import core
+
+main() {
+	exit := core.exit
+	exit()
+}

tests/programs_test.go

@@ -68,6 +68,7 @@ var programs = []struct {
 	{"struct", 0},
 	{"len", 0},
 	{"cast", 0},
+	{"function-pointer", 0},
 }
 
 func TestPrograms(t *testing.T) {