Fix typo: true -> false

Author: liufengyun

compiler/src/dotty/tools/dotc/transform/patmat/Space.scala

@@ -292,7 +292,7 @@ object SpaceEngine {
     (unapp.symbol.is(Synthetic) && unapp.symbol.owner.linkedClass.is(Case)) ||  // scala2 compatibility
     (patSize != -1 && productArity(unappResult) == patSize) || {
       val isEmptyTp = extractorMemberType(unappResult, nme.isEmpty, unapp.sourcePos)
-      isEmptyTp <:< ConstantType(Constant(true))
+      isEmptyTp <:< ConstantType(Constant(false))
     }
   }
 
@@ -307,7 +307,7 @@ object SpaceEngine {
     isProductSeqMatch(unappResult, patSize) ||
     {
       val isEmptyTp = extractorMemberType(unappResult, nme.isEmpty, unapp.sourcePos)
-      isEmptyTp <:< ConstantType(Constant(true))
+      isEmptyTp <:< ConstantType(Constant(false))
     }
   }
 }

docs/docs/reference/changed-features/pattern-matching.md

@@ -55,7 +55,7 @@ A usage of a fixed-arity extractor is irrefutable if one of the following condit
 - `U = true`
 - the extractor is used as a product match
 - `U = Some[T]` (for Scala2 compatibility)
-- `U <: R` and `U <: { def isEmpty: true }`
+- `U <: R` and `U <: { def isEmpty: false }`
 
 ### Variadic Extractors
 
@@ -88,7 +88,7 @@ A usage of a variadic extractor is irrefutable if one of the following condition
 
 - the extractor is used directly as a sequence match or product-sequence match
 - `U = Some[T]` (for Scala2 compatibility)
-- `U <: R` and `U <: { def isEmpty: true }`
+- `U <: R` and `U <: { def isEmpty: false }`
 
 ## Boolean Match
 

tests/patmat/irrefutable.scala

@@ -36,7 +36,7 @@ object ExProduct {
 // isEmpty/get
 
 trait Res {
-  def isEmpty: true = true
+  def isEmpty: false = false
   def get: Int
 }