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Add warning for synchronized on value classes #20301

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Add warning for synchronized on value classes #20301

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d89fbaa
Add warning for synchronized on value classes
nox213 Apr 30, 2024
f8b2b2a
Fix check files
nox213 Apr 30, 2024
68c30d1
Move the test file to tests/warn directory
nox213 May 1, 2024
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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 @@ -200,7 +200,7 @@ enum ErrorMessageID(val isActive: Boolean = true) extends java.lang.Enum[ErrorMe
case MatchTypeNoCasesID // errorNumber: 184
case UnimportedAndImportedID // errorNumber: 185
case ImplausiblePatternWarningID // errorNumber: 186
case SynchronizedCallOnBoxedClassID // errorNumber: 187
case SynchronizedCallOnValueID // errorNumber: 187
case VarArgsParamCannotBeGivenID // errorNumber: 188
case ExtractorNotFoundID // errorNumber: 189
case PureUnitExpressionID // errorNumber: 190
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10 changes: 5 additions & 5 deletions compiler/src/dotty/tools/dotc/reporting/messages.scala
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Expand Up @@ -2443,13 +2443,13 @@ class UnqualifiedCallToAnyRefMethod(stat: untpd.Tree, method: Symbol)(using Cont
|you intended.$getClassExtraHint"""
}

class SynchronizedCallOnBoxedClass(stat: tpd.Tree)(using Context)
extends Message(SynchronizedCallOnBoxedClassID) {
class SynchronizedCallOnValue(stat: tpd.Tree)(using Context)
extends Message(SynchronizedCallOnValueID) {
def kind = MessageKind.PotentialIssue
def msg(using Context) = i"Suspicious ${hl("synchronized")} call on boxed class"
def msg(using Context) = i"Suspicious ${hl("synchronized")} call on value"
def explain(using Context) =
i"""|You called the ${hl("synchronized")} method on a boxed primitive. This might not be what
|you intended."""
i"""|You called the ${hl("synchronized")} method on a boxed primitive or on a class extending ${hl("AnyVal")}.
|This might not be what you intended."""
}

class ExtensionNullifiedByMember(method: Symbol, target: Symbol)(using Context)
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8 changes: 7 additions & 1 deletion compiler/src/dotty/tools/dotc/typer/RefChecks.scala
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Expand Up @@ -1155,6 +1155,11 @@ object RefChecks {
then report.warning(ExtensionNullifiedByMember(sym, target.typeSymbol), sym.srcPos)
end checkExtensionMethods

def checkSynchronizedCallOnValue(tree: Tree)(using Context): Unit =
if tree.symbol == defn.Object_synchronized
&& ctx.owner.enclosingClass.isValueClass then
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This won't do the right thing for an imported synchronized.

You shouldn't look at the context owner, but at the prefix of tree.tpe.

report.warning(SynchronizedCallOnValue(tree), tree)

/** Verify that references in the user-defined `@implicitNotFound` message are valid.
* (i.e. they refer to a type variable that really occurs in the signature of the annotated symbol.)
*/
Expand Down Expand Up @@ -1326,11 +1331,12 @@ class RefChecks extends MiniPhase { thisPhase =>

override def transformIdent(tree: Ident)(using Context): Tree =
checkAnyRefMethodCall(tree)
checkSynchronizedCallOnValue(tree)
tree

override def transformSelect(tree: tpd.Select)(using Context): tpd.Tree =
if defn.ScalaBoxedClasses().contains(tree.qualifier.tpe.typeSymbol) && tree.name == nme.synchronized_ then
report.warning(SynchronizedCallOnBoxedClass(tree), tree.srcPos)
report.warning(SynchronizedCallOnValue(tree), tree.srcPos)
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This should probably reuse checkSynchronizedCallOnValue. Otherwise explicit selections on AnyVal won't do the right thing, AFAICT.

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We tried the following during the Spree:

//> using options -explain
class A(val s: String) extends AnyVal
def Test =
  val a = A("hello")
  a.synchronized { println("hello, world") } // warn

And this is already throws an error:

 ~/scala-snippets-5 scalac foo.scala
-- [E008] Not Found Error: foo.scala:5:4 ---------------------------------------
5 |  a.synchronized { println("hello, world") } // warn
  |  ^^^^^^^^^^^^^^
  |value synchronized is not a member of A, but could be made available as an extension method.
  |
  |The following import might fix the problem:
  |
  |  import scala.reflect.Selectable.reflectiveSelectable
  |
1 error found

Is this the case you have in mind?

Anyway, I guess it might be nice to use the same logic both for Select and Apply.

tree
}

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18 changes: 9 additions & 9 deletions tests/warn/17284.check
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@@ -1,30 +1,30 @@
-- [E187] Potential Issue Warning: tests/warn/17284.scala:4:6 ----------------------------------------------------------
4 | 451.synchronized {} // warn
| ^^^^^^^^^^^^^^^^
| Suspicious synchronized call on boxed class
| Suspicious synchronized call on value
|---------------------------------------------------------------------------------------------------------------------
| Explanation (enabled by `-explain`)
|- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
| You called the synchronized method on a boxed primitive. This might not be what
| you intended.
| You called the synchronized method on a boxed primitive or on a class extending AnyVal.
| This might not be what you intended.
---------------------------------------------------------------------------------------------------------------------
-- [E187] Potential Issue Warning: tests/warn/17284.scala:8:4 ----------------------------------------------------------
8 | x.synchronized {} // warn
| ^^^^^^^^^^^^^^
| Suspicious synchronized call on boxed class
| Suspicious synchronized call on value
|---------------------------------------------------------------------------------------------------------------------
| Explanation (enabled by `-explain`)
|- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
| You called the synchronized method on a boxed primitive. This might not be what
| you intended.
| You called the synchronized method on a boxed primitive or on a class extending AnyVal.
| This might not be what you intended.
---------------------------------------------------------------------------------------------------------------------
-- [E187] Potential Issue Warning: tests/warn/17284.scala:11:7 ---------------------------------------------------------
11 | true.synchronized {} // warn
| ^^^^^^^^^^^^^^^^^
| Suspicious synchronized call on boxed class
| Suspicious synchronized call on value
|--------------------------------------------------------------------------------------------------------------------
| Explanation (enabled by `-explain`)
|- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
| You called the synchronized method on a boxed primitive. This might not be what
| you intended.
| You called the synchronized method on a boxed primitive or on a class extending AnyVal.
| This might not be what you intended.
--------------------------------------------------------------------------------------------------------------------
6 changes: 3 additions & 3 deletions tests/warn/i17266.check
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Expand Up @@ -23,12 +23,12 @@
-- [E187] Potential Issue Warning: tests/warn/i17266.scala:22:4 --------------------------------------------------------
22 | 1.synchronized { // warn
| ^^^^^^^^^^^^^^
| Suspicious synchronized call on boxed class
| Suspicious synchronized call on value
|--------------------------------------------------------------------------------------------------------------------
| Explanation (enabled by `-explain`)
|- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
| You called the synchronized method on a boxed primitive. This might not be what
| you intended.
| You called the synchronized method on a boxed primitive or on a class extending AnyVal.
| This might not be what you intended.
--------------------------------------------------------------------------------------------------------------------
-- [E181] Potential Issue Warning: tests/warn/i17266.scala:108:2 -------------------------------------------------------
108 | wait() // warn
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10 changes: 10 additions & 0 deletions tests/warn/i17493.check
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@@ -0,0 +1,10 @@
-- [E187] Potential Issue Warning: tests/warn/i17493.scala:3:10 --------------------------------------------------------
3 | def g = synchronized { println("hello, world") } // warn
| ^^^^^^^^^^^^
| Suspicious synchronized call on value
|---------------------------------------------------------------------------------------------------------------------
| Explanation (enabled by `-explain`)
|- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
| You called the synchronized method on a boxed primitive or on a class extending AnyVal.
| This might not be what you intended.
---------------------------------------------------------------------------------------------------------------------
4 changes: 4 additions & 0 deletions tests/warn/i17493.scala
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@@ -0,0 +1,4 @@
//> using options -explain
class A(val s: String) extends AnyVal {
def g = synchronized { println("hello, world") } // warn
}