Summary

The JLS disallows the use of type annotations for variables declared using 'var'. javac is unfortunately not enforcing this limitation in all cases, and this ticket strives to fix that.

Problem

More specifically, since introduction of var in JDK 10, the type annotations have been disallowed on local variables, enhanced for statements variables and try-with-resources variables. When bindinding patterns were introduced in JDK 16, the restriction was enhanced to binding patterns in the JLS. And the restriction has been enhanced to lambda parameters declared using 'var' in JDK/JLS 20 (JDK-8295807). javac is sadly not enforcing this restriction for:

• lambda var parameters
• enhanced for statements variables
• partly for binding patterns (compile-time error is reported, but a wrong kind of error)

Solution

javac will properly enforce the restriction on present of type variables, and use of type variables in combination with var will lead to a compile-time error.

Specification

No change in an existing specification. javac behavior will be adjusted to more closely match the JLS. The proposed behavior is:

• for lambda var parameters, type annotations in combination with var will produce a compile-time error when --source >= 20/--release >= 20.
• for enhanced for statement variables, type annotations in combination with var will produce a compile-time error for all source versions
• for binding patterns, the proper error will be added for type annotations in combination with var