fallible ergonomics

examples/programs/errors/main.bro

@@ -8,6 +8,8 @@ DetailError :: union(enum) {
 	empty void
 }
 
+BasicOrDetail :: alias BasicError | DetailError
+
 Left :: enum {
 	left
 }
@@ -30,6 +32,7 @@ Box :: alias BoxA | BoxB
 
 maybe func(value i32) i32 ! BasicError {
 	if (value == 0) return .bad
+	if (value < 0) return .worse
 	return value + 1
 }
 
@@ -44,6 +47,41 @@ with_detail func(value i32) i32 ! DetailError {
 	return value
 }
 
+via_widen func(value i32) i32 ! BasicOrDetail {
+	unwrapped :: try maybe(value)
+	return unwrapped + 2
+}
+
+catch_basic func(value i32) i32 {
+	return maybe(value) catch |e| {
+		if (e == .bad) {
+			yield 21
+		} else {
+			yield 22
+		}
+	}
+}
+
+catch_detail func(value i32) i32 {
+	return with_detail(value) catch |e| {
+		match e {
+			.code |n|: yield n + 30
+			.empty:   yield 40
+		}
+	}
+}
+
+catch_widen func(value i32) i32 {
+	return via_widen(value) catch |e| {
+		match e {
+			.bad:      yield 50
+			.worse:    yield 51
+			.code |n|: yield n
+			.empty:    yield 52
+		}
+	}
+}
+
 pick func(value Both) i32 {
 	match value {
 		.left:  return 10
@@ -67,8 +105,15 @@ main func() i32 {
 	d :: via_try(0) catch 11
 	e :: with_detail(0) catch 13
 	f :: with_detail(2) catch 99
+	g :: catch_basic(0)
+	h :: catch_basic(-1)
+	i :: catch_detail(0)
+	j :: catch_detail(1)
+	k :: via_widen(3) catch 99
+	l :: catch_widen(0)
+	m :: catch_widen(-1)
 
-	acc = acc + a + b + c + d + e + f
+	acc = acc + a + b + c + d + e + f + g + h + i + j + k + l + m
 	acc = acc + pick(.left)
 	r Right = .right
 	acc = acc + pick(r)
@@ -77,6 +122,6 @@ main func() i32 {
 	empty BoxB = .b
 	acc = acc + payload(empty)
 
-	# 7 + 5 + 5 + 11 + 13 + 2 + 10 + 20 + 8 + 3 = 84
-	return acc - 84
+	# 7 + 5 + 5 + 11 + 13 + 2 + 21 + 22 + 35 + 40 + 6 + 50 + 51 + 10 + 20 + 8 + 3 = 309
+	return acc - 309
 }