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felixmulderfelixmulder
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Don't warn for erasure on arrays with value types
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3 files changed

+61
-28
lines changed

3 files changed

+61
-28
lines changed

‎compiler/src/dotty/tools/dotc/transform/IsInstanceOfEvaluator.scala

Lines changed: 8 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -128,8 +128,14 @@ class IsInstanceOfEvaluator extends MiniPhaseTransform { thisTransformer =>
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val selClassNonFinal = selClass && !(selector.typeSymbol is Final)
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val selFinalClass = selClass && (selector.typeSymbol is Final)
130130
val selTypeParam = tree.args.head.tpe.widen match {
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case AppliedType(tycon, args) =>
132-
ctx.uncheckedWarning(
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case tp @ AppliedType(tycon, args) =>
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// If the type is Array[X] where x extends AnyVal, this shouldn't yield a warning:
133+
val illegalComparison = !(tp.isRef(defn.ArrayClass) && {
134+
args.head.derivesFrom(defn.AnyValClass) ||
135+
args.head.isRef(defn.AnyClass)
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})
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if (illegalComparison) ctx.uncheckedWarning(
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ErasedType(hl"""|Since type parameters are erased, you should not match on them in
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|${"match"} expressions."""),
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tree.pos

‎tests/repl/erasure.check

Lines changed: 53 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,53 @@
1+
scala> def unsafeCast[S](a: Any) = a match { case s: S => s; case _ => ??? }
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-- [E035] Erased Type Unchecked Warning: <console> -----------------------------
3+
4 |def unsafeCast[S](a: Any) = a match { case s: S => s; case _ => ??? }
4+
| ^
5+
| abstract type pattern is unchecked since it is eliminated by erasure
6+
7+
longer explanation available when compiling with `-explain`
8+
def unsafeCast[S](a: Any): [S] => (a: Any)S
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scala> unsafeCast[String](1)
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java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.String
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at .<init>(<console>:6)
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at .<clinit>(<console>)
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at RequestResult$.<init>(<console>:3)
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at RequestResult$.<clinit>(<console>)
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at RequestResult$result(<console>)
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at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
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at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.jav...
18+
scala> class A; def unsafeCast2[S <: A](a: Any) = a match { case s: S => s; case _ => ??? }
19+
-- [E035] Erased Type Unchecked Warning: <console> -----------------------------
20+
4 |class A; def unsafeCast2[S <: A](a: Any) = a match { case s: S => s; case _ => ??? }
21+
| ^
22+
| abstract type pattern is unchecked since it is eliminated by erasure
23+
24+
longer explanation available when compiling with `-explain`
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defined class A
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def unsafeCast2[S <: A](a: Any): [S <: A] => (a: Any)S
27+
scala> def matchArray1[A](xs: Array[A]) = xs match { case xs: Array[Int] => xs; case xs: Array[A] => ??? }
28+
def matchArray1[A](xs: Array[A]): [A] => (xs: Array[A])Array[Int]
29+
scala> def matchArray2[A](xs: Array[Any]) = xs match { case xs: Array[Int] => xs; case xs: Array[A] => ??? }
30+
-- [E035] Erased Type Unchecked Warning: <console> -----------------------------
31+
5 |def matchArray2[A](xs: Array[Any]) = xs match { case xs: Array[Int] => xs; case xs: Array[A] => ??? }
32+
| ^
33+
| abstract type pattern is unchecked since it is eliminated by erasure
34+
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longer explanation available when compiling with `-explain`
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def matchArray2[A](xs: Array[Any]): [A] => (xs: Array[Any])Array[Int]
37+
scala> def matchArray3[A](xs: Array[A]) = xs match { case xs: Array[Int] => xs; case xs: Array[AnyRef] => ???; case xs: Array[Any] => ??? }
38+
-- [E035] Erased Type Unchecked Warning: <console> -----------------------------
39+
5 |def matchArray3[A](xs: Array[A]) = xs match { case xs: Array[Int] => xs; case xs: Array[AnyRef] => ???; case xs: Array[Any] => ??? }
40+
| ^
41+
| abstract type pattern is unchecked since it is eliminated by erasure
42+
43+
longer explanation available when compiling with `-explain`
44+
def matchArray3[A](xs: Array[A]): [A] => (xs: Array[A])Array[Int]
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scala> def matchArray4(xs: Array[Any]) = xs match { case xs: Array[Int] => xs; case xs: Array[A] => ???; case xs: Array[Any] => ??? }
46+
-- [E035] Erased Type Unchecked Warning: <console> -----------------------------
47+
5 |def matchArray4(xs: Array[Any]) = xs match { case xs: Array[Int] => xs; case xs: Array[A] => ???; case xs: Array[Any] => ??? }
48+
| ^
49+
| abstract type pattern is unchecked since it is eliminated by erasure
50+
51+
longer explanation available when compiling with `-explain`
52+
def matchArray4(xs: Array[Any]): Array[Int]
53+
scala> :quit

‎tests/repl/errmsgs.check

Lines changed: 0 additions & 26 deletions
Original file line numberDiff line numberDiff line change
@@ -78,30 +78,4 @@ scala> class Foo() { def bar: Int = 1 }; val foo = new Foo(); foo.barr
7878
4 |class Foo() { def bar: Int = 1 }; val foo = new Foo(); foo.barr
7979
| ^^^^^^^^
8080
| value `barr` is not a member of Foo(foo) - did you mean `foo.bar`?
81-
scala> def unsafeCast[S](a: Any) = a match { case s: S => s; case _ => ??? }
82-
-- [E034] Erased Type Unchecked Warning: <console> -----------------------------
83-
4 |def unsafeCast[S](a: Any) = a match { case s: S => s; case _ => ??? }
84-
| ^
85-
| abstract type pattern is unchecked since it is eliminated by erasure
86-
87-
longer explanation available when compiling with `-explain`
88-
def unsafeCast[S](a: Any): [S] => (a: Any)S
89-
scala> unsafeCast[String](1)
90-
java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.String
91-
at .<init>(<console>:6)
92-
at .<clinit>(<console>)
93-
at RequestResult$.<init>(<console>:3)
94-
at RequestResult$.<clinit>(<console>)
95-
at RequestResult$result(<console>)
96-
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
97-
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.jav...
98-
scala> class A; def unsafeCast2[S <: A](a: Any) = a match { case s: S => s; case _ => ??? }
99-
-- [E034] Erased Type Unchecked Warning: <console> -----------------------------
100-
4 |class A; def unsafeCast2[S <: A](a: Any) = a match { case s: S => s; case _ => ??? }
101-
| ^
102-
| abstract type pattern is unchecked since it is eliminated by erasure
103-
104-
longer explanation available when compiling with `-explain`
105-
defined class A
106-
def unsafeCast2[S <: A](a: Any): [S <: A] => (a: Any)S
10781
scala> :quit

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