Add error message about double definition (#1589) #4064
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| Original file line number | Diff line number | Diff line change |
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@@ -627,7 +627,7 @@ trait Checking { | |
| def explanation = | ||
| if (!decl.isRealMethod) "" | ||
| else "\n(the definitions have matching type signatures)" | ||
| ctx.error(DoubleDeclaration(decl, other), decl.pos) | ||
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There was a problem hiding this comment. You must not drop the info on matching type signatures. Either you preserve it or you figure out why it's there by walking For instance, for this code from #597 we need to explain users that this sort of overload is not allowed: trait A
trait B
class Test {
def foo(x: List[A]): Function1[A, A] = ???
def foo(x: List[B]): Function2[B, B, B] = ??? //error
}I think this code would make a good testcase. There was a problem hiding this comment. Thank you for your feedback. If I understand correctly, the code given in #597 should not compile. I added a test case in tests/neg/, but the tests failed because it compiles successfully. There was a problem hiding this comment. Uh! I just wanted to say "please don't remove the message", but I should still have tried. The behavior of So, here is the current behavior: scala> class Test {
def foo(x: List[A]): Function1[A, A] = ???
def foo(x: List[B]): Function1[B, B] = ??? // error
}
3 | def foo(x: List[B]): Function1[B, B] = ??? // error
| ^
| method foo is already defined as method foo: (x: List[A]): A => A
| (the definitions have matching type signatures)That code fails because, while the overload is "acceptable" (you can tell at call site which one to call, I forget the right word), the two functions erase to the same "signature" (which here means JVM signature, according to @smarter). The regression I was observing is that here "the definitions have matching type signatures" is important. I'll accept this PR as soon as that message is restored with the same check (I'm not sure why Here or in further PRs, we might want some clearer message there. Scalac gives: <console>:15: error: double definition:
def foo(x: List[A]): A => A at line 14 and
def foo(x: List[B]): B => B at line 15
have same type after erasure: (x: List)Function1
def foo(x: List[B]): Function1[B, B] = ??? // errorInstead, class Test {
def foo(x: List[A]): Function1[A, A] = ???
def foo(x: List[B]): Function2[B, B, B] = ??? //error
}is supported because the overload is acceptable and they erase to different JVM signatures (because of the different return types). Finally, this code is rejected because this overload isn't acceptable: scala> class Test {
def foo(x: List[A]): Function1[A, A] = ???
def foo(x: List[A]): Function2[B, B, B] = ??? // error
}
3 | def foo(x: List[A]): Function2[B, B, B] = ??? // error
| ^
| method foo is already defined as method foo: (x: List[A]): A => A
| (the definitions have matching type signatures)This should arguably give a different error: scala> class Test {
| def foo(x: List[A]): Function1[A, A] = ???
| def foo(x: List[A]): Function2[B, B, B] = ??? // error
| }
<console>:15: error: method foo is defined twice;
the conflicting method foo was defined at line 14:16
def foo(x: List[A]): Function2[B, B, B] = ??? // error
^ |
||
| } | ||
| if (decl is Synthetic) doubleDefError(other, decl) | ||
| else doubleDefError(decl, other) | ||
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maybe keep using
explanationin the DoubleDeclaration class, or movedef explanationthere?