conditional optional unwrapping

examples/programs/conditional_unwrap/main.bro

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+# Milestone 5: conditional unwrapping `if opt |v| { ... }`.
+# Tests a present optional binds and unwraps, a none takes the else branch, and
+# that optional pointers (?*T) unwrap the same way.
+
+main :: func() i32 {
+	total i32 = 0
+
+	# present optional scalar -> binds v to the unwrapped value
+	a ?i32 = 40
+	if a |v| {
+		total = total + v          # 40
+	} else {
+		total = total + 99
+	}
+
+	# none -> else branch taken; the binding is not in scope there
+	b ?i32 = none
+	if b |v| {
+		total = total + v
+	} else {
+		total = total + 2          # 42
+	}
+
+	# optional pointer present -> binds q to a non-null @i32; deref proves it
+	n i32 = 0
+	p ?@i32 = &n
+	if p |q| {
+		total = total + q^         # +0
+	}
+
+	# optional pointer none -> skipped
+	z ?@i32 = none
+	if z |q| {
+		total = total + 1000
+	}
+
+	return total                   # expect exit code 42
+}