lang: Add more tests for function

lang/interpret_test/TestAstFunc2/func-math1.output

@@ -0,0 +1,2 @@
+Vertex: test[sq1: 13]
+Vertex: test[sq2: 42]

lang/interpret_test/TestAstFunc2/func-math1/main.mcl

@@ -0,0 +1,17 @@
+import "fmt"
+
+# function statement
+func sq1($x, $y) {
+	$y + $x * $x
+}
+
+# function expression
+$sq2 = func($x, $y) {
+	$y + $x * $x
+}
+
+$x1 = sq1(3, 4) # 3^2 + 4 = 13
+$x2 = $sq2(7, -7) # 7^2 + 2 = 42
+
+test fmt.printf("sq1: %d", $x1) {}
+test fmt.printf("sq2: %d", $x2) {}

lang/interpret_test/TestAstFunc2/func-shadowing1.output

@@ -0,0 +1 @@
+Vertex: test[hello world]

lang/interpret_test/TestAstFunc2/func-shadowing1/main.mcl

@@ -0,0 +1,5 @@
+$foo = "bad1"
+func bar($foo) {
+	"hello " + $foo # shadows parent var
+}
+test bar("world") {}

lang/interpret_test/TestAstFunc2/func-shadowing2.output

@@ -0,0 +1 @@
+Vertex: test[hello world]

lang/interpret_test/TestAstFunc2/func-shadowing2/main.mcl

@@ -0,0 +1,5 @@
+$foo = "bad1"
+$bar = func($foo) {
+	"hello " + $foo # shadows parent var
+}
+test $bar("world") {}

lang/interpret_test/TestAstFunc2/invalid-function-call.output

@@ -0,0 +1 @@
+# err: err3: expected: Func, got: Int

lang/interpret_test/TestAstFunc2/invalid-function-call/main.mcl

@@ -0,0 +1,10 @@
+import "fmt"
+
+# function expression
+$notfn = 42
+
+$x = $notfn(7)
+
+print "msg" {
+	msg => fmt.printf("notfn: %d", $x),
+}