compiler: add support for new language features of Go 1.17

testdata/go1.17.go

@@ -0,0 +1,34 @@
+package main
+
+// Test new language features introduced in Go 1.17:
+// https://tip.golang.org/doc/go1.17#language
+// Once this becomes the minimum Go version of TinyGo, these tests should be
+// merged with the regular slice tests.
+
+import "unsafe"
+
+func main() {
+	// Test conversion from array to slice.
+	slice1 := []int{1, 2, 3, 4}
+	arr1 := (*[4]int)(slice1)
+	arr1[1] = -2
+	arr1[2] = 20
+	println("slice to array pointer:", arr1[0], arr1[1], arr1[2], arr1[3])
+
+	// Test unsafe.Add.
+	arr2 := [...]int{1, 2, 3, 4}
+	*(*int)(unsafe.Add(unsafe.Pointer(&arr2[0]), unsafe.Sizeof(int(1))*1)) = 5
+	*addInt(&arr2[0], 2) = 8
+	println("unsafe.Add array:", arr2[0], arr2[1], arr2[2], arr2[3])
+
+	// Test unsafe.Slice.
+	arr3 := [...]int{1, 2, 3, 4}
+	slice3 := unsafe.Slice(&arr3[1], 3)
+	slice3[0] = 9
+	slice3[1] = 15
+	println("unsafe.Slice array:", len(slice3), cap(slice3), slice3[0], slice3[1], slice3[2])
+}
+
+func addInt(ptr *int, index uintptr) *int {
+	return (*int)(unsafe.Add(unsafe.Pointer(ptr), unsafe.Sizeof(int(1))*index))
+}

testdata/go1.17.txt

@@ -0,0 +1,3 @@
+slice to array pointer: 1 -2 20 4
+unsafe.Add array: 1 5 8 4
+unsafe.Slice array: 3 3 9 15 4