expression property

The expression that follows the atSign.

The syntax of an annotation is fixed: identifier ('.' identifier)? typeArguments? ('.' identifier)? arguments?. With arguments, the expression is always a ConstructorInvocation, even before resolution. Without arguments, the parser produces a chain of ParsedUnqualifiedName, ParsedNameAccess, and ParsedTypeArguments, which resolution replaces, depending on what the names denote, with:

• a NameExpression, such as foo, p.foo, or C.foo;
• a TypeLiteral, such as C or p.C<int>;
• a ConstructorTearOff, such as C.named or C<int>.named;
• a FunctionInstantiation, such as f<int>.

An annotation is resolved like the same expression written without a keyword in a constant context. A valid annotation is either a read of a constant variable or an invocation of a constant constructor. For any other expression resolution reports a diagnostic, and the annotation has no value.