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Warn when open modifier is redundant (traits, abstract classes and local classes) #11971

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Merged
merged 1 commit into from
Apr 19, 2021
Merged

Warn when open modifier is redundant (traits, abstract classes and local classes) #11971

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12 changes: 10 additions & 2 deletions compiler/src/dotty/tools/dotc/typer/Checking.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -425,6 +425,7 @@ object Checking {
/** Check that symbol's definition is well-formed. */
def checkWellFormed(sym: Symbol)(using Context): Unit = {
def fail(msg: Message) = report.error(msg, sym.srcPos)
def warn(msg: Message) = report.warning(msg, sym.srcPos)

def checkWithDeferred(flag: FlagSet) =
if (sym.isOneOf(flag))
Expand Down Expand Up @@ -464,8 +465,15 @@ object Checking {
fail(em"only classes can be ${(sym.flags & ClassOnlyFlags).flagsString}")
if (sym.is(AbsOverride) && !sym.owner.is(Trait))
fail(AbstractOverrideOnlyInTraits(sym))
if (sym.is(Trait) && sym.is(Final))
fail(TraitsMayNotBeFinal(sym))
if sym.is(Trait) then
if sym.is(Final) then
fail(TraitsMayNotBeFinal(sym))
else if sym.is(Open) then
warn(RedundantModifier(Open))
if sym.isAllOf(Abstract | Open) then
warn(RedundantModifier(Open))
if sym.is(Open) && sym.isLocal then
warn(RedundantModifier(Open))
// Skip ModuleVal since the annotation will also be on the ModuleClass
if (sym.hasAnnotation(defn.TailrecAnnot) && !sym.isOneOf(Method | ModuleVal))
fail(TailrecNotApplicable(sym))
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1 change: 1 addition & 0 deletions tests/neg-custom-args/fatal-warnings/i11963a.scala
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@@ -0,0 +1 @@
open trait Foo // error
1 change: 1 addition & 0 deletions tests/neg-custom-args/fatal-warnings/i11963b.scala
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@@ -0,0 +1 @@
open abstract class Foo // error
6 changes: 6 additions & 0 deletions tests/neg-custom-args/fatal-warnings/i11963c.scala
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@@ -0,0 +1,6 @@
object Test {
def foo: Any = {
open class Bar // error
new Bar
}
}