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Improve "constructor proxy shadows outer" handling (#17154)
2 parents 3948ecc + 80b165c commit 3a830c8

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8 files changed

+167
-25
lines changed

8 files changed

+167
-25
lines changed

‎compiler/src/dotty/tools/dotc/reporting/ErrorMessageID.scala‎

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Original file line numberDiff line numberDiff line change
@@ -190,6 +190,7 @@ enum ErrorMessageID(val isActive: Boolean = true) extends java.lang.Enum[ErrorMe
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case InlineGivenShouldNotBeFunctionID // errorNumber 174
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case ValueDiscardingID // errorNumber 175
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case UnusedNonUnitValueID // errorNumber 176
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case ConstrProxyShadowsID // errorNumber 177
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def errorNumber = ordinal - 1
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‎compiler/src/dotty/tools/dotc/reporting/messages.scala‎

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Original file line numberDiff line numberDiff line change
@@ -1305,6 +1305,37 @@ extends SyntaxMsg(VarArgsParamMustComeLastID) {
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13061306
import typer.Typer.BindingPrec
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class ConstrProxyShadows(proxy: TermRef, shadowed: Type, shadowedIsApply: Boolean)(using Context)
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extends ReferenceMsg(ConstrProxyShadowsID), NoDisambiguation:
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def clsString(using Context) = proxy.symbol.companionClass.showLocated
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def shadowedString(using Context) = shadowed.termSymbol.showLocated
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def appClause = if shadowedIsApply then " the apply method of" else ""
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def appSuffix = if shadowedIsApply then ".apply" else ""
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def msg(using Context) =
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i"""Reference to constructor proxy for $clsString
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|shadows outer reference to $shadowedString
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|
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|The instance needs to be created with an explicit `new`."""
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def explain(using Context) =
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i"""There is an ambiguity in the meaning of the call
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|
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| ${proxy.symbol.name}(...)
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|
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|It could mean creating an instance of $clsString with
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|
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| new ${proxy.symbol.companionClass.name}(...)
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|
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|Or it could mean calling$appClause $shadowedString as in
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|
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| ${shadowed.termSymbol.name}$appSuffix(...)
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|
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|To disambiguate, use an explicit `new` if you mean the former,
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|or use a full prefix for ${shadowed.termSymbol.name} if you mean the latter."""
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end ConstrProxyShadows
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class AmbiguousReference(name: Name, newPrec: BindingPrec, prevPrec: BindingPrec, prevCtx: Context)(using Context)
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extends ReferenceMsg(AmbiguousReferenceID), NoDisambiguation {
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‎compiler/src/dotty/tools/dotc/typer/Typer.scala‎

Lines changed: 31 additions & 13 deletions
Original file line numberDiff line numberDiff line change
@@ -544,22 +544,40 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
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unimported = saved1
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foundUnderScala2 = saved2
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def checkNotShadowed(ownType: Type) = ownType match
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case ownType: TermRef if ownType.symbol.is(ConstructorProxy) =>
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val shadowed = findRef(name, pt, EmptyFlags, ConstructorProxy, tree.srcPos)
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if shadowed.exists then
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report.error(
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em"""Reference to constructor proxy for ${ownType.symbol.companionClass.showLocated}
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|shadows outer reference to ${shadowed.termSymbol.showLocated}""", tree.srcPos)
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case _ =>
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/** Normally, returns `ownType` except if `ownType` is a constructor proxy,
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* and there is another shadowed type accessible with the same name that is not:
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* - if the prototype is an application:
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* - if the shadowed type has a method alternative or an apply method,
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* issue an ambiguity error
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* - otherwise again return `ownType`
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* - if the prototype is not an application, return the shadowed type
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*/
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def checkNotShadowed(ownType: Type): Type =
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ownType match
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case ownType: TermRef if ownType.symbol.is(ConstructorProxy) =>
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findRef(name, pt, EmptyFlags, ConstructorProxy, tree.srcPos) match
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case shadowed: TermRef =>
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pt match
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case pt: FunOrPolyProto =>
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def err(shadowedIsApply: Boolean) =
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report.error(ConstrProxyShadows(ownType, shadowed, shadowedIsApply), tree.srcPos)
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if shadowed.denot.hasAltWith(sd => sd.symbol.is(Method, butNot = Accessor)) then
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err(shadowedIsApply = false)
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else if shadowed.member(nme.apply).hasAltWith(_.symbol.is(Method, butNot = Accessor)) then
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err(shadowedIsApply = true)
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case _ =>
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return shadowed
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case shadowed =>
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case _ =>
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ownType
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def setType(ownType: Type): Tree =
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checkNotShadowed(ownType)
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val tree1 = ownType match
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case ownType: NamedType if !prefixIsElidable(ownType) =>
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ref(ownType).withSpan(tree.span)
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val checkedType = checkNotShadowed(ownType)
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val tree1 = checkedType match
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case checkedType: NamedType if !prefixIsElidable(checkedType) =>
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ref(checkedType).withSpan(tree.span)
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case _ =>
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tree.withType(ownType)
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tree.withType(checkedType)
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val tree2 = toNotNullTermRef(tree1, pt)
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checkLegalValue(tree2, pt)
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tree2

‎docs/_docs/reference/other-new-features/creator-applications.md‎

Lines changed: 6 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -47,8 +47,12 @@ be selected with `apply` (or be applied to arguments, in which case the `apply`
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inserted).
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Constructor proxies are also not allowed to shadow normal definitions. That is,
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if an identifier resolves to a constructor proxy, and the same identifier is also
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defined or imported in some other scope, an ambiguity is reported.
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an ambiguity is reported, if
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- an identifier resolves to a constructor proxy,
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- the same identifier is also defined or imported in some other scope,
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- the other reference can be applied to a (possibly empty) parameter list. That
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is, it refers either to a method or to a value containing an apply method as member.
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## Motivation
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‎tests/neg-custom-args/explain/constructor-proxy-shadowing.check‎

Lines changed: 75 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,75 @@
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-- [E177] Reference Error: tests/neg-custom-args/explain/constructor-proxy-shadowing.scala:10:12 -----------------------
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10 | val x = A22("") // error: shadowing
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| ^^^
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| Reference to constructor proxy for class A22 in class A
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| shadows outer reference to method A22 in object Test
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|
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| The instance needs to be created with an explicit `new`.
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|--------------------------------------------------------------------------------------------------------------------
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| Explanation (enabled by `-explain`)
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|- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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| There is an ambiguity in the meaning of the call
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|
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| A22(...)
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|
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| It could mean creating an instance of class A22 in class A with
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|
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| new A22(...)
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|
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| Or it could mean calling method A22 in object Test as in
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|
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| A22(...)
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|
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| To disambiguate, use an explicit `new` if you mean the former,
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| or use a full prefix for A22 if you mean the latter.
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--------------------------------------------------------------------------------------------------------------------
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-- [E177] Reference Error: tests/neg-custom-args/explain/constructor-proxy-shadowing.scala:11:12 -----------------------
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11 | val y = A33("") // error: shadowing
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| ^^^
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| Reference to constructor proxy for class A33 in class A
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| shadows outer reference to object A33 in object Test
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|
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| The instance needs to be created with an explicit `new`.
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|--------------------------------------------------------------------------------------------------------------------
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| Explanation (enabled by `-explain`)
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|- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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| There is an ambiguity in the meaning of the call
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|
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| A33(...)
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|
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| It could mean creating an instance of class A33 in class A with
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|
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| new A33(...)
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|
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| Or it could mean calling the apply method of object A33 in object Test as in
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|
46+
| A33.apply(...)
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|
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| To disambiguate, use an explicit `new` if you mean the former,
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| or use a full prefix for A33 if you mean the latter.
50+
--------------------------------------------------------------------------------------------------------------------
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-- [E177] Reference Error: tests/neg-custom-args/explain/constructor-proxy-shadowing.scala:16:8 ------------------------
52+
16 |val x = Seq(3) // error: shadowing
53+
| ^^^
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| Reference to constructor proxy for class Seq
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| shadows outer reference to getter Seq in package scala
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|
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| The instance needs to be created with an explicit `new`.
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|--------------------------------------------------------------------------------------------------------------------
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| Explanation (enabled by `-explain`)
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|- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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| There is an ambiguity in the meaning of the call
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|
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| Seq(...)
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|
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| It could mean creating an instance of class Seq with
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|
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| new Seq(...)
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|
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| Or it could mean calling the apply method of getter Seq in package scala as in
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|
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| Seq.apply(...)
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|
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| To disambiguate, use an explicit `new` if you mean the former,
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| or use a full prefix for Seq if you mean the latter.
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--------------------------------------------------------------------------------------------------------------------

‎tests/neg-custom-args/explain/constructor-proxy-shadowing.scala‎

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@@ -0,0 +1,16 @@
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object Test extends App {
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def A22(s: String): String = s
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class A33(s: String)
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object A33:
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def apply(s: String) = ???
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class A {
8+
class A22(s: String)
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class A33(s: String)
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val x = A22("") // error: shadowing
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val y = A33("") // error: shadowing
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}
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}
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class Seq(n: Int)
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val x = Seq(3) // error: shadowing

‎tests/neg/constructor-proxy-shadowing.scala‎

Lines changed: 0 additions & 10 deletions
This file was deleted.

‎tests/pos/constr-proxy-shadowing.scala‎

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,7 @@
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class Number(n: Int)
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val x = Number(3)
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class Seq(n: Int)
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val y = Seq
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