make buildNormalizedPath() @safe #6357
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WalterBright
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| result = asNormalizedPath(result).array; | ||
| return cast(typeof(return)) result; | ||
| auto result = asNormalizedPath(chained).array; // .array returns a copy, so we know it is unique | ||
| return () @trusted { return assumeUnique(result); } (); |
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I realize that this has become an accepted way to do @trusted. But I think it actually goes against the idea behind it.
The @trusted snippet doesn't ensure safety by itself. It relies on the rest of the code not messing with result. That means, you can trigger undefined behavior by editing @safe code. Exactly what should not be possible.
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| return cast(typeof(return)) result; | ||
| auto result = asNormalizedPath(chained); | ||
| // .array returns a copy, so we know it is unique | ||
| return () @trusted { return assumeUnique(result.array); } (); |
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Hmm. If .array returns a unique array, how come the compiler can't infer it? I would have thought that it should be inferred as pure, and the compiler would have been able to implicitly convert it to immutable without a @trusted escape.
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Pure isn't enough to infer the result is immutable.
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Shrink the @trusted to the smallest bit of the function that needs it. The rest is to follow the convention that
resultis for the return value.