IdentifierList = identifier { "," identifier } .
ExpressionList = Expression { "," Expression } .
</pre>

<p>
If the type is present, all constants take the type specified, and
the expressions must be <a href="#Assignability">assignable</a> to that type.
If the type is omitted, the constants take the
individual types of the corresponding expressions.
If the expression values are untyped <a href="#Constants">constants</a>,

ExpressionList = Expression { "," Expression } .
</pre>

<p>
If the type is present, all constants take the type specified, and
the expressions must be <a href="#Assignability">assignable</a> to that type,
which must not be a type parameter.
If the type is omitted, the constants take the
individual types of the corresponding expressions.
If the expression values are untyped <a href="#Constants">constants</a>,

				ok = false // broke compatibility
			}
		case len(required) == 0 || (len(features) > 0 && required[0] > features[0]):
			newFeature := take(&features)
			fmt.Fprintf(w, "+%s\n", newFeature)
			ok = false // feature not in api/next/*
		default:
			take(&required)
			take(&features)
		}
	}

	return ok
}

// aliasReplacer applies type aliases to earlier API files,