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mgroovy edited comment on GROOVY-8992 at 2/16/19 6:46 PM: ---------------------------------------------------------- * That's why I suggested it: The result of the closure call is either R1, R2 or R3 (depending on parameters passed), so you can read it as "or", or as a sort-of a union of the three types. * It also would have the advantage of allowing a more concise syntax, since the vertical bar seperates more clearly than the semicolon, so you don't need the brackets. * (to me especially the ():R is very inelegant) * Hmmm - but I see what you mean: Would Groovy ever support union types with vertical bar as the obvious operator, the syntax would clash... * On the other hand one could (if that ever happened / in the rare case of a union type) write: {code}Closure<(R1|S|T)|X:R2|(Y1|Y2),Z:R3>{code} i.e. simply bracket the union type. * Keep the frequent case concise, keep the rare case correct ;) was (Author: emge): * That's why I suggested it: The result of the closure call is either R1, R2 or R3 (depending on parameters passed), so you can read it as "or", or as a sort-of a union of the three types. * It also would have the advantage of allowing a more concise syntax, since the vertical bar seperates more clearly than the semicolon, so you don't need the brackets. * (to me especially the ():R is very inelegant) * Hmmm - but I see what you mean: Would Groovy ever support union types with vertical bar as the obvious operator, the syntax would clash... > [GEP]Polish the generics type syntax for closure > ------------------------------------------------ > > Key: GROOVY-8992 > URL: https://issues.apache.org/jira/browse/GROOVY-8992 > Project: Groovy > Issue Type: Improvement > Reporter: Daniel Sun > Assignee: Daniel Sun > Priority: Major > > h2. 1. Background > Currently the syntax specifying the generics type for closure is quite > verbose and not type safe, e.g. > {code:java} > @ClosureParams(value=SimpleType.class, options="groovy.sql.Sql") Closure<V> > closure > {code} > h2. 2. Solutions > ① × I propose to make the above code groovier, but the proposed "arrow > syntax making it hard to read, in particular when the argument types have > generics themselves" reminded by [~melix], e.g. > {code:java} > Closure<groovy.sql.Sql -> V> > {code} > ② √ Suggestions of [~blackdrag] are much groovier for all cases: > {code:java} > Closure<groovy.sql.Sql : V> > {code} > ③ √ In the meanwhile, [~blackdrag] proposed other variants of the generics > type syntax for closure to handle "polymorphic closures (aka closures which > accept different kind of arguments)" reminded by [~melix] > {code:java} > Closure<():R1; (X):R2; (Y, Z):R3> > {code} > h2. 3. Benefits > ① The new syntax of generics type for closure is much more concise and > readable: > {code:java} > Closure<groovy.sql.Sql:V> > {code} > {code:java} > Closure<Sql:V> // qualified name is not necessary if using imports > {code} > *VS* > {code:java} > @ClosureParams(value=SimpleType.class, options="groovy.sql.Sql") Closure<V> > {code} > ② Type checking can be completed in the compilation time, so we can find > errors in time, e.g. {{@ClosureParams(... options="groovy.sql.SqlAbc")}} of > annotation specifies the type with string literal, but the type does not > exist, so we can not the error in the compilation time. On the contrast, > {{Closure<groovy.sql.SqlAbc:V>}} can make compiler help us find type errors > in the compilation time. > ③ Better IDE support because of using the types instead of string literals > for types > h2. 4. Rationale > In order to keep "consistency between using annotations and a type-checking > only feature" reminded by [~melix], I propose to transform the groovier code > to the original code when compiling, e.g. > {{Closure<groovy.sql.Sql:V>}} > will be transformed to > {{@ClosureParams(value=SimpleType.class, options="groovy.sql.Sql") > Closure<V>}} > h2. 5. Discussions in the dev mailing list > [http://groovy.329449.n5.nabble.com/About-polish-the-generics-type-syntax-for-closure-tt5756586.html] -- This message was sent by Atlassian JIRA (v7.6.3#76005)