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Fix 14682: fix overriding check in mergeSingleDenot #14755

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Mar 23, 2022
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5 changes: 3 additions & 2 deletions compiler/src/dotty/tools/dotc/core/Denotations.scala
Original file line number Diff line number Diff line change
Expand Up @@ -469,11 +469,12 @@ object Denotations {
else if sym1.is(Method) && !sym2.is(Method) then 1
else 0

val relaxedOverriding = ctx.explicitNulls && (sym1.is(JavaDefined) || sym2.is(JavaDefined))
val matchLoosely = sym1.matchNullaryLoosely || sym2.matchNullaryLoosely

if symScore <= 0 && info2.overrides(info1, matchLoosely, checkClassInfo = false) then
if symScore <= 0 && info2.overrides(info1, relaxedOverriding, matchLoosely, checkClassInfo = false) then
denot2
else if symScore >= 0 && info1.overrides(info2, matchLoosely, checkClassInfo = false) then
else if symScore >= 0 && info1.overrides(info2, relaxedOverriding, matchLoosely, checkClassInfo = false) then
denot1
else
val jointInfo = infoMeet(info1, info2, safeIntersection)
Expand Down
20 changes: 12 additions & 8 deletions compiler/src/dotty/tools/dotc/core/Types.scala
Original file line number Diff line number Diff line change
Expand Up @@ -1071,21 +1071,25 @@ object Types {

/** Is this type a legal type for member `sym1` that overrides another
* member `sym2` of type `that`? This is the same as `<:<`, except that
* @param relaxedCheck if true type `Null` becomes a subtype of non-primitive value types in TypeComparer.
* @param matchLoosely if true the types `=> T` and `()T` are seen as overriding each other.
* @param checkClassInfo if true we check that ClassInfos are within bounds of abstract types
*/
final def overrides(that: Type, matchLoosely: => Boolean, checkClassInfo: Boolean = true)(using Context): Boolean = {
final def overrides(that: Type, relaxedCheck: Boolean, matchLoosely: => Boolean, checkClassInfo: Boolean = true)(using Context): Boolean = {
def widenNullary(tp: Type) = tp match {
case tp @ MethodType(Nil) => tp.resultType
case _ => tp
}
!checkClassInfo && this.isInstanceOf[ClassInfo]
|| (this.widenExpr frozen_<:< that.widenExpr)
|| matchLoosely && {
val this1 = widenNullary(this)
val that1 = widenNullary(that)
((this1 `ne` this) || (that1 `ne` that)) && this1.overrides(that1, false, checkClassInfo)
}
val overrideCtx = if relaxedCheck then ctx.relaxedOverrideContext else ctx
inContext(overrideCtx) {
!checkClassInfo && this.isInstanceOf[ClassInfo]
|| (this.widenExpr frozen_<:< that.widenExpr)
|| matchLoosely && {
val this1 = widenNullary(this)
val that1 = widenNullary(that)
((this1 `ne` this) || (that1 `ne` that)) && this1.overrides(that1, relaxedCheck, false, checkClassInfo)
}
}
}

/** Is this type close enough to that type so that members
Expand Down
8 changes: 3 additions & 5 deletions compiler/src/dotty/tools/dotc/transform/OverridingPairs.scala
Original file line number Diff line number Diff line change
Expand Up @@ -217,11 +217,9 @@ object OverridingPairs:
else
// releaxed override check for explicit nulls if one of the symbols is Java defined,
// force `Null` to be a subtype of non-primitive value types during override checking.
val overrideCtx = if ctx.explicitNulls && (member.is(JavaDefined) || other.is(JavaDefined))
then ctx.relaxedOverrideContext else ctx
val relaxedOverriding = ctx.explicitNulls && (member.is(JavaDefined) || other.is(JavaDefined))
member.name.is(DefaultGetterName) // default getters are not checked for compatibility
|| memberTp.overrides(otherTp,
member.matchNullaryLoosely || other.matchNullaryLoosely || fallBack
)(using overrideCtx)
|| memberTp.overrides(otherTp, relaxedOverriding,
member.matchNullaryLoosely || other.matchNullaryLoosely || fallBack)

end OverridingPairs
5 changes: 2 additions & 3 deletions compiler/src/dotty/tools/dotc/transform/ResolveSuper.scala
Original file line number Diff line number Diff line change
Expand Up @@ -113,9 +113,8 @@ object ResolveSuper {
// Since the super class can be Java defined,
// we use relaxed overriding check for explicit nulls if one of the symbols is Java defined.
// This forces `Null` to be a subtype of non-primitive value types during override checking.
val overrideCtx = if ctx.explicitNulls && (sym.is(JavaDefined) || acc.is(JavaDefined))
then ctx.relaxedOverrideContext else ctx
if !otherTp.overrides(accTp, matchLoosely = true)(using overrideCtx) then
val relaxedOverriding = ctx.explicitNulls && (sym.is(JavaDefined) || acc.is(JavaDefined))
if !otherTp.overrides(accTp, relaxedOverriding, matchLoosely = true) then
report.error(IllegalSuperAccessor(base, memberName, targetName, acc, accTp, other.symbol, otherTp), base.srcPos)
bcs = bcs.tail
}
Expand Down
2 changes: 1 addition & 1 deletion compiler/src/dotty/tools/dotc/typer/RefChecks.scala
Original file line number Diff line number Diff line change
Expand Up @@ -767,7 +767,7 @@ object RefChecks {
for (mbrd <- self.member(name).alternatives) {
val mbr = mbrd.symbol
val mbrType = mbr.info.asSeenFrom(self, mbr.owner)
if (!mbrType.overrides(mbrd.info, matchLoosely = true))
if (!mbrType.overrides(mbrd.info, relaxedCheck = false, matchLoosely = true))
report.errorOrMigrationWarning(
em"""${mbr.showLocated} is not a legal implementation of `$name` in $clazz
| its type $mbrType
Expand Down
3 changes: 1 addition & 2 deletions compiler/test/dotty/tools/dotc/CompilationTests.scala
Original file line number Diff line number Diff line change
Expand Up @@ -52,7 +52,6 @@ class CompilationTests {
),
compileFile("tests/pos-special/typeclass-scaling.scala", defaultOptions.and("-Xmax-inlines", "40")),
compileFile("tests/pos-special/i7296.scala", defaultOptions.and("-source", "future", "-deprecation", "-Xfatal-warnings")),
compileFile("tests/pos-special/notNull.scala", defaultOptions.and("-Yexplicit-nulls")),
compileDir("tests/pos-special/adhoc-extension", defaultOptions.and("-source", "future", "-feature", "-Xfatal-warnings")),
compileFile("tests/pos-special/i7575.scala", defaultOptions.andLanguageFeature("dynamics")),
compileFile("tests/pos-special/kind-projector.scala", defaultOptions.and("-Ykind-projector")),
Expand Down Expand Up @@ -137,7 +136,6 @@ class CompilationTests {
compileFilesInDir("tests/neg-custom-args/erased", defaultOptions.and("-language:experimental.erasedDefinitions")),
compileFilesInDir("tests/neg-custom-args/allow-double-bindings", allowDoubleBindings),
compileFilesInDir("tests/neg-custom-args/allow-deep-subtypes", allowDeepSubtypes),
compileFilesInDir("tests/neg-custom-args/explicit-nulls", defaultOptions.and("-Yexplicit-nulls")),
compileFilesInDir("tests/neg-custom-args/no-experimental", defaultOptions.and("-Yno-experimental")),
compileDir("tests/neg-custom-args/impl-conv", defaultOptions.and("-Xfatal-warnings", "-feature")),
compileDir("tests/neg-custom-args/i13946", defaultOptions.and("-Xfatal-warnings", "-feature")),
Expand Down Expand Up @@ -249,6 +247,7 @@ class CompilationTests {
compileFilesInDir("tests/explicit-nulls/pos-separate", explicitNullsOptions),
compileFilesInDir("tests/explicit-nulls/pos-patmat", explicitNullsOptions and "-Xfatal-warnings"),
compileFilesInDir("tests/explicit-nulls/unsafe-common", explicitNullsOptions and "-language:unsafeNulls"),
compileFile("tests/explicit-nulls/pos-special/i14682.scala", explicitNullsOptions and "-Ysafe-init"),
)
}.checkCompile()

Expand Down
Original file line number Diff line number Diff line change
@@ -1,27 +1,27 @@
-- [E007] Type Mismatch Error: tests/neg-custom-args/explicit-nulls/byname-nullables.scala:19:24 -----------------------
-- [E007] Type Mismatch Error: tests/explicit-nulls/neg/byname-nullables.scala:19:24 -----------------------------------
19 | if x != null then f(x) // error: f is call-by-name
| ^
| Found: (x : String | Null)
| Required: String
|
| longer explanation available when compiling with `-explain`
-- Error: tests/neg-custom-args/explicit-nulls/byname-nullables.scala:43:32 --------------------------------------------
-- Error: tests/explicit-nulls/neg/byname-nullables.scala:43:32 --------------------------------------------------------
43 | if x != null then f(identity(x), 1) // error: dropping not null check fails typing
| ^^^^^^^^^^^
| This argument was typed using flow assumptions about mutable variables
| but it is passed to a by-name parameter where such flow assumptions are unsound.
| Wrapping the argument in `byName(...)` fixes the problem by disabling the flow assumptions.
|
| `byName` needs to be imported from the `scala.compiletime` package.
-- Error: tests/neg-custom-args/explicit-nulls/byname-nullables.scala:68:24 --------------------------------------------
-- Error: tests/explicit-nulls/neg/byname-nullables.scala:68:24 --------------------------------------------------------
68 | if x != null then f(x, 1) // error: dropping not null check typechecks OK, but gives incompatible result type
| ^
| This argument was typed using flow assumptions about mutable variables
| but it is passed to a by-name parameter where such flow assumptions are unsound.
| Wrapping the argument in `byName(...)` fixes the problem by disabling the flow assumptions.
|
| `byName` needs to be imported from the `scala.compiletime` package.
-- [E134] Type Error: tests/neg-custom-args/explicit-nulls/byname-nullables.scala:81:22 --------------------------------
-- [E134] Type Error: tests/explicit-nulls/neg/byname-nullables.scala:81:22 --------------------------------------------
81 | if x != null then f(byName(x), 1) // error: none of the overloaded methods match argument types
| ^
| None of the overloaded alternatives of method f in object Test7 with types
Expand Down
Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
-- Error: tests/neg-custom-args/explicit-nulls/byname-nullables1.scala:10:6 --------------------------------------------
-- Error: tests/explicit-nulls/neg/byname-nullables1.scala:10:6 --------------------------------------------------------
10 | f(x.fld != null) // error
| ^^^^^^^^^^^^^
| This argument was typed using flow assumptions about mutable variables
Expand Down
Original file line number Diff line number Diff line change
@@ -1,18 +1,18 @@
-- [E134] Type Error: tests/neg-custom-args/explicit-nulls/i7883.scala:6:11 --------------------------------------------
-- [E134] Type Error: tests/explicit-nulls/neg/i7883.scala:6:11 --------------------------------------------------------
6 | case r(hd, tl) => Some((hd, tl)) // error // error // error
| ^
| None of the overloaded alternatives of method unapplySeq in class Regex with types
| (m: scala.util.matching.Regex.Match): Option[List[String]]
| (c: Char): Option[List[Char]]
| (s: CharSequence): Option[List[String]]
| match arguments (String | Null)
-- [E006] Not Found Error: tests/neg-custom-args/explicit-nulls/i7883.scala:6:30 ---------------------------------------
-- [E006] Not Found Error: tests/explicit-nulls/neg/i7883.scala:6:30 ---------------------------------------------------
6 | case r(hd, tl) => Some((hd, tl)) // error // error // error
| ^^
| Not found: hd
|
| longer explanation available when compiling with `-explain`
-- [E006] Not Found Error: tests/neg-custom-args/explicit-nulls/i7883.scala:6:34 ---------------------------------------
-- [E006] Not Found Error: tests/explicit-nulls/neg/i7883.scala:6:34 ---------------------------------------------------
6 | case r(hd, tl) => Some((hd, tl)) // error // error // error
| ^^
| Not found: tl
Expand Down
27 changes: 27 additions & 0 deletions tests/explicit-nulls/pos-special/i14682.scala
Original file line number Diff line number Diff line change
@@ -0,0 +1,27 @@
class C1:
sealed abstract class Name {
type ThisName <: Name
def compareTo(that: ThisName): Int = ???
}

class LocalName extends Name with Comparable[LocalName] {
type ThisName = LocalName
}

val localName = LocalName()
println(localName)
var count = 0

class C2:
sealed abstract class Name {
type ThisName <: Name
def compareTo(that: ThisName | Null): Int = ???
}

class LocalName extends Name with Comparable[LocalName] {
type ThisName = LocalName
}

val localName = LocalName()
println(localName)
var count = 0
File renamed without changes.