commit | d17859ca116cade68c69b1d580f5612ec162a648 | [log] [tgz] |
---|---|---|
author | Paul Berry <paulberry@google.com> | Thu May 24 23:07:55 2018 +0000 |
committer | commit-bot@chromium.org <commit-bot@chromium.org> | Thu May 24 23:07:55 2018 +0000 |
tree | bbbd99dbb1c59ce1d9ca217e2aeff24c3cc48ae5 | |
parent | ca7d545df8a26c6c4514cda96d0168c41edb934a [diff] |
Observatory strong mode fixes: make callback parameter types more general. This CL addresses a code pattern where a method expects its parameter to have a certain type, but that method is torn off and passed as a callback to another method expecting its parameter type to be more general. For example: void f(int i) { ... } void g(void callback(Object o)) { ... } void h() { g(f); // Error: () -> int is not a subtype of () -> Object } This is a strong mode error because the type system cannot guarantee that the value pased to f will be an int. The solution is to broaden the type of the callback parameter so that it matches the type expected for the callback. In most cases, we insert an implicit downcast (by reassigning the parameter to a local variable with the expected type), which in Dart 2.0 semantics will result in a runtime check (similar to what happens in Dart 1.0 checked mode). Since the downcasts are implicit, the Dart 1.0 semantics are unchanged, so this should be a safe change. Change-Id: I9583ea194343b89b39305c9796cfad299a47943f Reviewed-on: https://dart-review.googlesource.com/55907 Commit-Queue: Paul Berry <paulberry@google.com> Reviewed-by: Ryan Macnak <rmacnak@google.com>
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