From 80e19f64608e5fb7c66f31d0b32364313ed467f0 Mon Sep 17 00:00:00 2001
From: Hamza Remmal <hamza@remmal.net>
Date: Sun, 23 Feb 2025 19:58:42 +0100
Subject: [PATCH] Warn universal extensions on opaque types
---
.../dotty/tools/dotc/typer/RefChecks.scala | 4 +--
tests/warn/i22232.check | 28 ++++++++++++++++
tests/warn/i22232.scala | 32 +++++++++++++++++++
3 files changed, 62 insertions(+), 2 deletions(-)
create mode 100644 tests/warn/i22232.check
create mode 100644 tests/warn/i22232.scala
diff --git a/compiler/src/dotty/tools/dotc/typer/RefChecks.scala b/compiler/src/dotty/tools/dotc/typer/RefChecks.scala
index d96b37dd3c55..43a2cc9d0b32 100644
--- a/compiler/src/dotty/tools/dotc/typer/RefChecks.scala
+++ b/compiler/src/dotty/tools/dotc/typer/RefChecks.scala
@@ -1168,7 +1168,7 @@ object RefChecks {
def explicit = Applications.stripImplicit(tp.stripPoly, wildcardOnly = true)
def hasImplicitParams = tp.stripPoly match { case mt: MethodType => mt.isImplicitMethod case _ => false }
val explicitInfo = sym.info.explicit // consider explicit value params
- val target = explicitInfo.firstParamTypes.head // required for extension method, the putative receiver
+ val target = explicitInfo.firstParamTypes.head.typeSymbol.info // required for extension method, the putative receiver
val methTp = explicitInfo.resultType // skip leading implicits and the "receiver" parameter
def hidden =
target.nonPrivateMember(sym.name)
@@ -1197,7 +1197,7 @@ object RefChecks {
sym.owner.info.member(getterName)
if getterDenot.exists
then report.warning(ExtensionHasDefault(sym), getterDenot.symbol.srcPos)
- if !target.typeSymbol.isOpaqueAlias && !sym.nextOverriddenSymbol.exists && hidden
+ if !sym.nextOverriddenSymbol.exists && hidden
then report.warning(ExtensionNullifiedByMember(sym, target.typeSymbol), sym.srcPos)
end checkExtensionMethods
diff --git a/tests/warn/i22232.check b/tests/warn/i22232.check
new file mode 100644
index 000000000000..cf3d6d4e004e
--- /dev/null
+++ b/tests/warn/i22232.check
@@ -0,0 +1,28 @@
+-- [E194] Potential Issue Warning: tests/warn/i22232.scala:3:23 --------------------------------------------------------
+3 | extension (c: C) def equals(that: Any): Boolean = false // warn
+ | ^
+ | Extension method equals will never be selected from type C
+ | because C already has a member with the same name and compatible parameter types.
+ |
+ | longer explanation available when compiling with `-explain`
+-- [E194] Potential Issue Warning: tests/warn/i22232.scala:9:25 --------------------------------------------------------
+9 | extension (d: D) def equals(that: Any): Boolean = false // warn
+ | ^
+ | Extension method equals will never be selected from type C
+ | because C already has a member with the same name and compatible parameter types.
+ |
+ | longer explanation available when compiling with `-explain`
+-- [E194] Potential Issue Warning: tests/warn/i22232.scala:13:38 -------------------------------------------------------
+13 | extension (arr: MyString[Byte]) def length: Int = 0 // warn
+ | ^
+ | Extension method length will never be selected from type String
+ | because String already has a member with the same name and compatible parameter types.
+ |
+ | longer explanation available when compiling with `-explain`
+-- [E194] Potential Issue Warning: tests/warn/i22232.scala:17:46 -------------------------------------------------------
+17 | extension [T <: MyString[Byte]](arr: T) def length: Int = 0 // warn
+ | ^
+ | Extension method length will never be selected from type String
+ | because String already has a member with the same name and compatible parameter types.
+ |
+ | longer explanation available when compiling with `-explain`
diff --git a/tests/warn/i22232.scala b/tests/warn/i22232.scala
new file mode 100644
index 000000000000..79b8317a7329
--- /dev/null
+++ b/tests/warn/i22232.scala
@@ -0,0 +1,32 @@
+class C
+object C:
+ extension (c: C) def equals(that: Any): Boolean = false // warn
+
+object X:
+ class C
+ opaque type D <: C = C
+ object D:
+ extension (d: D) def equals(that: Any): Boolean = false // warn
+
+object Upperbound1:
+ opaque type MyString[+T] <: String = String
+ extension (arr: MyString[Byte]) def length: Int = 0 // warn
+
+object Upperbound2:
+ opaque type MyString[+T] <: String = String
+ extension [T <: MyString[Byte]](arr: T) def length: Int = 0 // warn
+
+object Upperbound3:
+ opaque type MyString[+T] <: String = String
+ extension [T](arr: T) def length: Int = 0 // nowarn
+
+object NonUpperbound1:
+ opaque type MyString[+T] = String
+ extension (arr: MyString[Byte]) def length: Int = 0 // nowarn
+object NonUpperbound2:
+ opaque type MyString[+T] = String
+ extension [T <: MyString[Byte]](arr: T) def length2: Int = 0 // nowarn
+
+object NonUpperbound3:
+ opaque type MyString[+T] = String
+ extension [T](arr: T) def length: Int = 0 // nowarn