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Closes #4300 adds better worded pattern match unreachability warning #4552

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Merged
merged 6 commits into from
Jun 13, 2018
Merged

Closes #4300 adds better worded pattern match unreachability warning #4552

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becafe4
Closes #4300 adds better worded pattern match unreachability warning
zoltanelek May 21, 2018
6834571
changed pattern match reachability warning, to reflect more complex m…
zoltanelek Jun 8, 2018
f55d497
clearer error message for pattern matching on objects
zoltanelek Jun 8, 2018
215f0bf
Created a proper error message case class
zoltanelek Jun 8, 2018
bf7c85c
Common TypeTestAlwaysSucceeds warning case class for pattern match an…
zoltanelek Jun 10, 2018
1370dd1
Fixed formatting
zoltanelek Jun 10, 2018
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1 change: 1 addition & 0 deletions compiler/src/dotty/tools/dotc/reporting/diagnostic/ErrorMessageID.java
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Expand Up @@ -130,6 +130,7 @@ public enum ErrorMessageID {
DoubleDeclarationID,
MatchCaseOnlyNullWarningID,
ImportRenamedTwiceID,
TypeTestAlwaysSucceedsID,
;

public int errorNumber() {
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5 changes: 5 additions & 0 deletions compiler/src/dotty/tools/dotc/reporting/diagnostic/messages.scala
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Expand Up @@ -2117,4 +2117,9 @@ object messages {
val explanation: String = ""
}

case class TypeTestAlwaysSucceeds(foundCls: Symbol, testCls: Symbol)(implicit ctx: Context) extends Message(TypeTestAlwaysSucceedsID) {
val kind = "Syntax"
val msg = s"The highlighted type test will always succeed since the scrutinee type ($foundCls) is a subtype of ${testCls}"
val explanation = ""
}
}
5 changes: 2 additions & 3 deletions compiler/src/dotty/tools/dotc/transform/TypeTestsCasts.scala
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Expand Up @@ -10,6 +10,7 @@ import ValueClasses._
import SymUtils._
import core.Flags._
import util.Positions._
import reporting.diagnostic.messages.TypeTestAlwaysSucceeds
import reporting.trace


Expand Down Expand Up @@ -90,9 +91,7 @@ object TypeTestsCasts {

if (expr.tpe <:< testType)
if (expr.tpe.isNotNull) {
ctx.warning(
em"this will always yield true, since `$foundCls` is a subclass of `$testCls`",
expr.pos)
ctx.warning(TypeTestAlwaysSucceeds(foundCls, testCls), tree.pos)
constant(expr, Literal(Constant(true)))
}
else expr.testNotNull
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