Fix #9740: harden type checking for pattern match on objects #11327
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liufengyun
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test performance please |
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performance test scheduled: 13 job(s) in queue, 1 running. |
dwijnand
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Feb 8, 2021
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| // Case 3: Same as above; should match the second case and print the length of the string | ||
| any match { | ||
| case C(IsInt, i) if i < 10 => println(s"An Int less than 10") |
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There's no checkfile for neg tests?? Sounds very unstable to not verify the failure reasons...
I wanted to see on what grounds this now fails to compile.
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We tend to avoid check files as they incur maintenance overhead. In contrast, we check the line numbers of reported errors agree with the comments // error in the source code.
dwijnand
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Feb 8, 2021
We enforce that when pattern match on an object, the object should be a subtype of the scrutinee type. Reasons for doing so: - such code patterns usually implies hidden errors in the code - it's always safe/sound to reject the code We could check whether `equals` is overridden in the object, but - it complicates the protocol - overriding `equals` of object is also a bad practice - there is no sign that the slightly improved completeness is useful
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odersky
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Feb 23, 2021
| mapOver(tp) | ||
| } | ||
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| if tree.symbol.is(Module) |
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Would it make sense to check this also for other values that are not modules?
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We cannot check non-module values due to aliasing.
liufengyun
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Feb 24, 2021
This is a follow-up of scala#11327.
liufengyun
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This is a follow-up of scala#11327. We cannot generalize further without complications: ``` val b = 'b' 56 match case 'a' => case `b` => ```
liufengyun
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This is a follow-up of scala#11327. We cannot generalize further without complications: ``` val b = 'b' 56 match case 'a' => case `b` => ```
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Fix #9740: harden type checking for pattern match on objects
We enforce that when pattern match on an object, the object should be
a subtype of the scrutinee type. It aligns with Scala 2 behavior.
Reasons for doing so:
We could check whether
equalsis overridden in the object, butequalsof object is also a bad practice