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Merge pull request #5624 from dotty-staging/fix-#5546

Fix #5546: Disallow comparing opaque types under -language:strictEqua...

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Lines changed: 3 additions & 1 deletion

Original file line number	Diff line number	Diff line change
`@@ -831,11 +831,13 @@ trait Implicits { self: Typer =>`
`831`	`831`	`(other ne NoType) && !other.derivesFrom(defn.AnyValClass)`
`832`	`832`	`}`
`833`	`833`
	`834`	`+ // Map all non-opaque abstract types to their upper bound.`
	`835`	`+ // This is done to check whether such types might plausibly be comparable to each other.`
`834`	`836`	`val lift = new TypeMap {`
`835`	`837`	`def apply(t: Type): Type = t match {`
`836`	`838`	`case t: TypeRef =>`
`837`	`839`	`t.info match {`
`838`		`- case TypeBounds(lo, hi) if lo ne hi => apply(hi)`
	`840`	`+ case TypeBounds(lo, hi) if lo.ne(hi) &&!t.symbol.is(Opaque) => apply(hi)`
`839`	`841`	`case _ => t`
`840`	`842`	`}`
`841`	`843`	`case t: RefinedType =>`

Lines changed: 21 additions & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,21 @@`
	`1`	`+import language.strictEquality`
	`2`	`+`
	`3`	`+object O {`
	`4`	`+`
	`5`	`+ opaque type Meters = Double`
	`6`	`+ object Meters {`
	`7`	`+ def apply(d: Double): Meters = d`
	`8`	`+ val m: Meters = 1.0`
	`9`	`+ assert(m == 1.0) // OK`
	`10`	`+ }`
	`11`	`+ implicit def eqM: Eq[Meters, Meters] = Eq`
	`12`	`+`
	`13`	`+ opaque type Feet = Double`
	`14`	`+ object Feet { def apply(d: Double): Feet = d }`
	`15`	`+ implicit def eqF: Eq[Feet, Feet] = Eq`
	`16`	`+`
	`17`	`+ def main(args: Array[String]): Unit = {`
	`18`	`+ println(Feet(3) == Meters(3)) // error: cannot compare`
	`19`	`+ println(Feet(3) == 3.0) // error: cannot compare`
	`20`	`+ }`
	`21`	`+}`

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