Nate Biggs
9eba05482b
I suspect that when the list of type preserving selectors was created the first/last setters either didn't exist or were just overlooked. Any dynamic List could have its inferred type changed by these operations. Due to Dart2js's type representation this bug affects more than just dynamic lists. We track some simple values as part of the type system. So an operation that modifies a value can technically modify the type, as Dart2js represents it, even if the "real" type is preserved. In the added test we would represent the list literal's type as "List(length: 2, elementType: Bool(true))". Notice the type states the elementType is specifically true, not just bool. Thus the first/last operations are modifying that type. But since we aren't registering this type change, SSA optimizes away the call/index and inlines the element itself. Interestingly, this primarily manifested for bools due to a check in SSA: https://github.com/dart-lang/sdk/blob/main/pkg/compiler/lib/src/ssa/optimize.dart#L475 In that code we are inlining constant-like expressions for the arguments of static invocations (such as the argument to a Expect.isTrue call). However, a few lines earlier you will see we only inline bool constants: https://github.com/dart-lang/sdk/blob/main/pkg/compiler/lib/src/ssa/optimize.dart#L467 So when the list element type is anything other than a bool, this inlining does not trigger thus avoiding the bug. Bug: https://github.com/dart-lang/sdk/issues/53944 Change-Id: I4e893903f335fc99b13cf526736c27bb066a4bad Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/334420 Reviewed-by: Stephen Adams <sra@google.com> Commit-Queue: Nate Biggs <natebiggs@google.com>
Dart
A client-optimized language for fast apps on any platform
Dart is:
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Optimized for UI: Develop with a programming language specialized around the needs of user interface creation.
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Productive: Make changes iteratively: use hot reload to see the result instantly in your running app.
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Fast on all platforms: Compile to ARM & x64 machine code for mobile, desktop, and backend. Or compile to JavaScript for the web.
Dart's flexible compiler technology lets you run Dart code in different ways, depending on your target platform and goals:
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Dart Native: For programs targeting devices (mobile, desktop, server, and more), Dart Native includes both a Dart VM with JIT (just-in-time) compilation and an AOT (ahead-of-time) compiler for producing machine code.
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Dart Web: For programs targeting the web, Dart Web includes both a development time compiler (dartdevc) and a production time compiler (dart2js).
License & patents
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See LICENSE and PATENT_GRANT.
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