Call-style constructors instead of brace literals

Structs and enum variants are constructed with call syntax, and every named field must be named: Point(x: 1, y: 2), Shape.Circle(radius: 1.0). Tuple-style declarations are constructed positionally: Some(x), Meters(3). Patterns use the same syntax.

We chose this over Rust-style Point { x: 1, y: 2 }. In Rust, a brace literal is ambiguous after if, while, and match, because the brace could also start the block. Rust resolves this with a rule that bans struct literals in those positions, which makes the syntax context-sensitive. Principle 3 forbids context-sensitive syntax. With call style, construction looks the same for structs and variants, and the parser has no special case.

Consequences

• A construction is indistinguishable from a function call until name resolution runs. Tooling must resolve names before it can tell them apart.
• Developers coming from Rust will expect brace literals. Do not add them without revisiting this ADR.