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LYR-SEM0122

an unqualified call of a name two conformance blocks implement

error · spec 05-interfaces

A member is called by its bare name on a type that implements it separately in two conformance blocks, for two interfaces.

Explanation

When a type implements greet once in its Greeter block and once in its Waver block, the name belongs to each block; the call p.greet() says nothing about which one is meant. Both stay reachable through the interface they implement.

Qualify the call with the interface: Greeter.greet(p).

Wrong

interface Greeter { fn greet(): string; }
interface Waver { fn greet(): string; }

struct Person { name: string }

extend Person :: [Greeter] { fn greet(): string { return "hello"; } }
extend Person :: [Waver] { fn greet(): string { return "hi"; } }

fn main(): void {
    let p = Person { name = "ada" };
    let _ = p.greet();
}
interface Greeter { fn greet(): string; }
interface Waver { fn greet(): string; }

struct Person { name: string }

extend Person :: [Greeter] { fn greet(): string { return "hello"; } }
extend Person :: [Waver] { fn greet(): string { return "hi"; } }

fn main(): void {
    let p = Person { name = "ada" };
    let _ = Greeter.greet(p);
}