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Don't optimize explicitly written isInstanceOf tests away. #14715

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Merged
merged 4 commits into from
Mar 21, 2022
Merged

Don't optimize explicitly written isInstanceOf tests away. #14715

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effb9d1
Don't optimize explicitly written isInstanceOf tests away.
odersky Mar 19, 2022
1c42de7
Fix erroneous isInstanceOf test in compiler
odersky Mar 19, 2022
e501845
Warn about nonsensical isInstanceOf tests with `Nothing` as the scrut…
odersky Mar 20, 2022
9648c63
Fix wrong treatment of Super nodes in TailRec
odersky Mar 20, 2022
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2 changes: 1 addition & 1 deletion compiler/src/dotty/tools/dotc/reporting/ErrorMessageID.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -131,7 +131,7 @@ enum ErrorMessageID extends java.lang.Enum[ErrorMessageID]:
DoubleDefinitionID,
MatchCaseOnlyNullWarningID,
ImportRenamedTwiceID,
TypeTestAlwaysSucceedsID,
TypeTestAlwaysDivergesID,
TermMemberNeedsNeedsResultTypeForImplicitSearchID,
ClassCannotExtendEnumID,
ValueClassParameterMayNotBeCallByNameID,
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10 changes: 3 additions & 7 deletions compiler/src/dotty/tools/dotc/reporting/messages.scala
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Expand Up @@ -2177,13 +2177,9 @@ import transform.SymUtils._
def explain = ""
}

class TypeTestAlwaysSucceeds(scrutTp: Type, testTp: Type)(using Context) extends SyntaxMsg(TypeTestAlwaysSucceedsID) {
def msg = {
val addendum =
if (scrutTp != testTp) s" is a subtype of ${testTp.show}"
else " is the same as the tested type"
s"The highlighted type test will always succeed since the scrutinee type ${scrutTp.show}" + addendum
}
class TypeTestAlwaysDiverges(scrutTp: Type, testTp: Type)(using Context) extends SyntaxMsg(TypeTestAlwaysDivergesID) {
def msg =
s"This type test will never return a result since the scrutinee type ${scrutTp.show} does not contain any value."
Comment on lines -2180 to +2182
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These changes don't seem to belong to this commit.

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They are actually linked to the changes in TypeTestsCasts. We had an error TypeTestAlwaysSucceeds before but now we have a TypeTestAlwaysDiverges instead.

def explain = ""
}

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2 changes: 1 addition & 1 deletion compiler/src/dotty/tools/dotc/transform/TreeChecker.scala
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Expand Up @@ -418,7 +418,7 @@ class TreeChecker extends Phase with SymTransformer {
}

override def typedSuper(tree: untpd.Super, pt: Type)(using Context): Tree =
assert(tree.qual.tpe.isInstanceOf[ThisType], i"expect prefix of Super to be This, actual = ${tree.qual}")
assert(tree.qual.typeOpt.isInstanceOf[ThisType], i"expect prefix of Super to be This, actual = ${tree.qual}")
super.typedSuper(tree, pt)

override def typedTyped(tree: untpd.Typed, pt: Type)(using Context): Tree =
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