K2: repeat K1 representation for flexible type parameters

This commit changes the behavior of KT-59138 effectively declining it in 2.0.
However, we plan to implement KT-59138 behavior under a feature
flag in 2.0 (see KT-66447), and switch this feature on version 2.x.

Also, this commit implements the LC resolution about postponing
KT-57014 change. We don't have KT-57014 described behavior in 2.0 anymore.
However, we plan to implement a deprecation warning here, see KT-65578.

After this commit, 6 diagnostic tests become incorrectly broken:
- 5 tests from PurelyImplementedCollection group
- a test platformTypes/nullableTypeArgument.kt

This commit also breaks currently fixed-in-k2 KT-50134
(it is fixed again in the following commits),
as well as KT-58933 (it will remain not fixed till we enable KT-59138
behavior again).

#KT-65596 In Progress
#KT-57014 In Progress
#KT-58933 Submitted

compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/DeeplySubstitutedClassParameter.fir.txt

@@ -1,6 +1,6 @@
 public abstract interface DeeplySubstitutedClassParameter : R|kotlin/Any| {
-    public abstract interface Middle<E : R|kotlin/Any!|> : R|test/DeeplySubstitutedClassParameter.Super<ft<E & Any, E?>>| {
-        public abstract fun foo(p: R|ft<E & Any, E?>|): R|kotlin/Unit|
+    public abstract interface Middle<E : R|kotlin/Any!|> : R|test/DeeplySubstitutedClassParameter.Super<E!>| {
+        public abstract fun foo(p: R|E!|): R|kotlin/Unit|
 
     }
     public abstract interface Sub : R|test/DeeplySubstitutedClassParameter.Middle<kotlin/String!>| {
@@ -8,7 +8,7 @@ public abstract interface DeeplySubstitutedClassParameter : R|kotlin/Any| {
 
     }
     public abstract interface Super<T : R|kotlin/Any!|> : R|kotlin/Any| {
-        public abstract fun foo(p: R|ft<T & Any, T?>|): R|kotlin/Unit|
+        public abstract fun foo(p: R|T!|): R|kotlin/Unit|
 
         public abstract fun dummy(): R|kotlin/Unit|
 

compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/DeeplySubstitutedClassParameter2.fir.txt

@@ -1,12 +1,12 @@
 public abstract interface DeeplySubstitutedClassParameter2 : R|kotlin/Any| {
-    public abstract interface Middle<E : R|kotlin/Any!|> : R|test/DeeplySubstitutedClassParameter2.Super<ft<E & Any, E?>>| {
+    public abstract interface Middle<E : R|kotlin/Any!|> : R|test/DeeplySubstitutedClassParameter2.Super<E!>| {
     }
     public abstract interface Sub : R|test/DeeplySubstitutedClassParameter2.Middle<kotlin/String!>| {
         public abstract fun foo(p: R|kotlin/String!|): R|kotlin/Unit|
 
     }
     public abstract interface Super<T : R|kotlin/Any!|> : R|kotlin/Any| {
-        public abstract fun foo(p: R|ft<T & Any, T?>|): R|kotlin/Unit|
+        public abstract fun foo(p: R|T!|): R|kotlin/Unit|
 
         public abstract fun dummy(): R|kotlin/Unit|
 

compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/Kt3302.fir.txt

@@ -10,7 +10,7 @@ public abstract interface Kt3302 : R|kotlin/Any| {
 
     }
     public abstract interface LinkedHashMap<K : R|kotlin/Any!|, V : R|kotlin/Any!|> : R|kotlin/Any| {
-        public abstract fun put(key: R|ft<K & Any, K?>|, value: R|ft<V & Any, V?>|): R|ft<V & Any, V?>|
+        public abstract fun put(key: R|K!|, value: R|V!|): R|V!|
 
         public abstract fun dummy(): R|kotlin/Unit|
 

compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/OverrideWithErasedParameter.fir.txt

@@ -1,10 +1,10 @@
 public abstract interface OverrideWithErasedParameter : R|kotlin/Any| {
-    public abstract interface Sub<T : R|kotlin/Any!|> : R|test/OverrideWithErasedParameter.Super<ft<T & Any, T?>>| {
+    public abstract interface Sub<T : R|kotlin/Any!|> : R|test/OverrideWithErasedParameter.Super<T!>| {
         public abstract fun foo(o: R|kotlin/Any!|): R|kotlin/Unit|
 
     }
     public abstract interface Super<T : R|kotlin/Any!|> : R|kotlin/Any| {
-        public abstract fun foo(t: R|ft<T & Any, T?>|): R|kotlin/Unit|
+        public abstract fun foo(t: R|T!|): R|kotlin/Unit|
 
         public abstract fun dummy(): R|kotlin/Unit|
 

compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/SubclassFromGenericAndNot.fir.txt

@@ -1,6 +1,6 @@
 public abstract interface SubclassFromGenericAndNot : R|kotlin/Any| {
     public abstract interface Generic<T : R|kotlin/Any!|> : R|kotlin/Any| {
-        public abstract fun foo(key: R|ft<T & Any, T?>|): R|kotlin/Unit|
+        public abstract fun foo(key: R|T!|): R|kotlin/Unit|
 
         public abstract fun dummy(): R|kotlin/Unit|
 

compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/SubstitutedClassParameter.fir.txt

@@ -4,7 +4,7 @@ public abstract interface SubstitutedClassParameter : R|kotlin/Any| {
 
     }
     public abstract interface Super<T : R|kotlin/Any!|> : R|kotlin/Any| {
-        public abstract fun foo(p: R|ft<T & Any, T?>|): R|kotlin/Unit|
+        public abstract fun foo(p: R|T!|): R|kotlin/Unit|
 
         public abstract fun dummy(): R|kotlin/Unit|
 

compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/SubstitutedClassParameters.fir.txt

@@ -4,13 +4,13 @@ public abstract interface SubstitutedClassParameters : R|kotlin/Any| {
 
     }
     public abstract interface Super1<T : R|kotlin/Any!|> : R|kotlin/Any| {
-        public abstract fun foo(p: R|ft<T & Any, T?>|): R|kotlin/Unit|
+        public abstract fun foo(p: R|T!|): R|kotlin/Unit|
 
         public abstract fun dummy(): R|kotlin/Unit|
 
     }
     public abstract interface Super2<E : R|kotlin/Any!|> : R|kotlin/Any| {
-        public abstract fun foo(p: R|ft<E & Any, E?>|): R|kotlin/Unit|
+        public abstract fun foo(p: R|E!|): R|kotlin/Unit|
 
         public abstract fun dummy(): R|kotlin/Unit|
 

compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/DeeplySubstitutedClassParameter.fir.txt

@@ -1,6 +1,6 @@
 public abstract interface DeeplySubstitutedClassParameter : R|kotlin/Any| {
-    public abstract interface Middle<E : R|kotlin/Any!|> : R|test/DeeplySubstitutedClassParameter.Super<ft<E & Any, E?>>| {
-        public abstract fun foo(): R|ft<E & Any, E?>|
+    public abstract interface Middle<E : R|kotlin/Any!|> : R|test/DeeplySubstitutedClassParameter.Super<E!>| {
+        public abstract fun foo(): R|E!|
 
     }
     public abstract interface Sub : R|test/DeeplySubstitutedClassParameter.Middle<kotlin/String!>| {
@@ -8,7 +8,7 @@ public abstract interface DeeplySubstitutedClassParameter : R|kotlin/Any| {
 
     }
     public abstract interface Super<T : R|kotlin/Any!|> : R|kotlin/Any| {
-        public abstract fun foo(): R|ft<T & Any, T?>|
+        public abstract fun foo(): R|T!|
 
         public abstract fun dummy(): R|kotlin/Unit|
 

compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/DeeplySubstitutedClassParameter2.fir.txt

@@ -1,12 +1,12 @@
 public abstract interface DeeplySubstitutedClassParameter2 : R|kotlin/Any| {
-    public abstract interface Middle<E : R|kotlin/Any!|> : R|test/DeeplySubstitutedClassParameter2.Super<ft<E & Any, E?>>| {
+    public abstract interface Middle<E : R|kotlin/Any!|> : R|test/DeeplySubstitutedClassParameter2.Super<E!>| {
     }
     public abstract interface Sub : R|test/DeeplySubstitutedClassParameter2.Middle<kotlin/String!>| {
         public abstract fun foo(): R|kotlin/String!|
 
     }
     public abstract interface Super<T : R|kotlin/Any!|> : R|kotlin/Any| {
-        public abstract fun foo(): R|ft<T & Any, T?>|
+        public abstract fun foo(): R|T!|
 
         public abstract fun dummy(): R|kotlin/Unit|
 

compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/HalfSubstitutedTypeParameters.fir.txt

@@ -9,6 +9,6 @@ public abstract interface HalfSubstitutedTypeParameters : R|kotlin/Any| {
         public abstract fun dummy(): R|kotlin/Unit|
 
     }
-    public abstract interface TrickyList<X : R|kotlin/Any!|, E : R|kotlin/Any!|> : R|kotlin/collections/MutableList<ft<E & Any, E?>>| {
+    public abstract interface TrickyList<X : R|kotlin/Any!|, E : R|kotlin/Any!|> : R|kotlin/collections/MutableList<E!>| {
     }
 }

compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/SubclassFromGenericAndNot.fir.txt

@@ -1,6 +1,6 @@
 public abstract interface SubclassFromGenericAndNot : R|kotlin/Any| {
     public abstract interface Generic<T : R|kotlin/Any!|> : R|kotlin/Any| {
-        public abstract fun foo(): R|ft<T & Any, T?>|
+        public abstract fun foo(): R|T!|
 
         public abstract fun dummy(): R|kotlin/Unit|
 

compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/SubclassOfCollection.fir.txt

@@ -1,4 +1,4 @@
-public abstract interface SubclassOfCollection<E : R|kotlin/Any!|> : R|kotlin/collections/MutableCollection<ft<E & Any, E?>>| {
-    public abstract operator fun iterator(): R|@EnhancedNullability kotlin/collections/MutableIterator<ft<E & Any, E?>>|
+public abstract interface SubclassOfCollection<E : R|kotlin/Any!|> : R|kotlin/collections/MutableCollection<E!>| {
+    public abstract operator fun iterator(): R|@EnhancedNullability kotlin/collections/MutableIterator<E!>|
 
 }

compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/SubclassOfMapEntry.fir.txt

@@ -1,4 +1,4 @@
-public abstract interface SubclassOfMapEntry<K : R|kotlin/Any!|, V : R|kotlin/Any!|> : R|kotlin/collections/MutableMap.MutableEntry<ft<K & Any, K?>, ft<V & Any, V?>>| {
-    public abstract fun setValue(value: R|ft<V & Any, V?>|): R|ft<V & Any, V?>|
+public abstract interface SubclassOfMapEntry<K : R|kotlin/Any!|, V : R|kotlin/Any!|> : R|kotlin/collections/MutableMap.MutableEntry<K!, V!>| {
+    public abstract fun setValue(value: R|V!|): R|V!|
 
 }

compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/SubstitutedClassParameter.fir.txt

@@ -4,7 +4,7 @@ public abstract interface SubstitutedClassParameter : R|kotlin/Any| {
 
     }
     public abstract interface Super<T : R|kotlin/Any!|> : R|kotlin/Any| {
-        public abstract fun foo(): R|ft<T & Any, T?>|
+        public abstract fun foo(): R|T!|
 
         public abstract fun dummy(): R|kotlin/Unit|
 

compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/SubstitutedClassParameters.fir.txt

@@ -4,13 +4,13 @@ public abstract interface SubstitutedClassParameters : R|kotlin/Any| {
 
     }
     public abstract interface Super1<T : R|kotlin/Any!|> : R|kotlin/Any| {
-        public abstract fun foo(): R|ft<T & Any, T?>|
+        public abstract fun foo(): R|T!|
 
         public abstract fun dummy(): R|kotlin/Unit|
 
     }
     public abstract interface Super2<E : R|kotlin/Any!|> : R|kotlin/Any| {
-        public abstract fun foo(): R|ft<E & Any, E?>|
+        public abstract fun foo(): R|E!|
 
         public abstract fun dummy(): R|kotlin/Unit|
 

compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TypeParamOfClass.fir.txt

@@ -1,5 +1,5 @@
 public abstract interface TypeParamOfClass : R|kotlin/Any| {
-    public abstract interface Sub<T : R|kotlin/Any!|> : R|test/TypeParamOfClass.Super<ft<T & Any, T?>>| {
+    public abstract interface Sub<T : R|kotlin/Any!|> : R|test/TypeParamOfClass.Super<T!>| {
         public abstract fun foo(): R|@EnhancedNullability T & Any|
 
     }

compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/InheritNullability.fir.txt

@@ -1,10 +1,10 @@
 public abstract interface InheritNullability : R|kotlin/Any| {
     public abstract interface Sub : R|test/InheritNullability.Super| {
-        public abstract fun <B : R|kotlin/CharSequence!|> foo(b: R|ft<B & Any, B?>|): R|kotlin/Unit|
+        public abstract fun <B : R|kotlin/CharSequence!|> foo(b: R|B!|): R|kotlin/Unit|
 
     }
     public abstract interface Super : R|kotlin/Any| {
-        public abstract fun <A : R|kotlin/CharSequence!|> foo(a: R|ft<A & Any, A?>|): R|kotlin/Unit|
+        public abstract fun <A : R|kotlin/CharSequence!|> foo(a: R|A!|): R|kotlin/Unit|
 
     }
 }

compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/TwoBounds.fir.txt

@@ -1,10 +1,10 @@
 public abstract interface TwoBounds : R|kotlin/Any| {
     public abstract interface Sub : R|test/TwoBounds.Super| {
-        public abstract fun <B : R|kotlin/CharSequence!|, R|kotlin/Cloneable!|> foo(b: R|ft<B & Any, B?>|): R|kotlin/Unit|
+        public abstract fun <B : R|kotlin/CharSequence!|, R|kotlin/Cloneable!|> foo(b: R|B!|): R|kotlin/Unit|
 
     }
     public abstract interface Super : R|kotlin/Any| {
-        public abstract fun <A : R|kotlin/CharSequence!|, R|kotlin/Cloneable!|> foo(a: R|ft<A & Any, A?>|): R|kotlin/Unit|
+        public abstract fun <A : R|kotlin/CharSequence!|, R|kotlin/Cloneable!|> foo(a: R|A!|): R|kotlin/Unit|
 
     }
 }

compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/TwoSuperclasses.fir.txt

@@ -1,14 +1,14 @@
 public abstract interface TwoSuperclasses : R|kotlin/Any| {
     public abstract interface Sub : R|test/TwoSuperclasses.Super1|, R|test/TwoSuperclasses.Super2| {
-        public abstract fun <C : R|kotlin/CharSequence!|> foo(c: R|ft<C & Any, C?>|): R|kotlin/Unit|
+        public abstract fun <C : R|kotlin/CharSequence!|> foo(c: R|C!|): R|kotlin/Unit|
 
     }
     public abstract interface Super1 : R|kotlin/Any| {
-        public abstract fun <A : R|kotlin/CharSequence!|> foo(a: R|ft<A & Any, A?>|): R|kotlin/Unit|
+        public abstract fun <A : R|kotlin/CharSequence!|> foo(a: R|A!|): R|kotlin/Unit|
 
     }
     public abstract interface Super2 : R|kotlin/Any| {
-        public abstract fun <B : R|kotlin/CharSequence!|> foo(a: R|ft<B & Any, B?>|): R|kotlin/Unit|
+        public abstract fun <B : R|kotlin/CharSequence!|> foo(a: R|B!|): R|kotlin/Unit|
 
     }
 }

compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/TwoTypeParameters.fir.txt

@@ -1,10 +1,10 @@
 public abstract interface TwoTypeParameters : R|kotlin/Any| {
     public abstract interface Sub : R|test/TwoTypeParameters.Super| {
-        public abstract fun <B : R|kotlin/CharSequence!|, A : R|kotlin/Cloneable!|> foo(b: R|ft<B & Any, B?>|, a: R|ft<A & Any, A?>|): R|kotlin/Unit|
+        public abstract fun <B : R|kotlin/CharSequence!|, A : R|kotlin/Cloneable!|> foo(b: R|B!|, a: R|A!|): R|kotlin/Unit|
 
     }
     public abstract interface Super : R|kotlin/Any| {
-        public abstract fun <A : R|kotlin/CharSequence!|, B : R|kotlin/Cloneable!|> foo(a: R|ft<A & Any, A?>|, b: R|ft<B & Any, B?>|): R|kotlin/Unit|
+        public abstract fun <A : R|kotlin/CharSequence!|, B : R|kotlin/Cloneable!|> foo(a: R|A!|, b: R|B!|): R|kotlin/Unit|
 
     }
 }

compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/UseParameterAsUpperBound.fir.txt

@@ -1,12 +1,12 @@
 public abstract interface UseParameterAsUpperBound : R|kotlin/Any| {
     public abstract interface Sub : R|test/UseParameterAsUpperBound.Super| {
-        public abstract fun <B : R|kotlin/Any!|, A : R|ft<B & Any, B?>|> foo(b: R|ft<B & Any, B?>|, a: R|ft<A & Any, A?>|): R|kotlin/Unit|
+        public abstract fun <B : R|kotlin/Any!|, A : R|B!|> foo(b: R|B!|, a: R|A!|): R|kotlin/Unit|
 
-        public abstract fun <A : R|kotlin/Any!|, B : R|ft<A & Any, A?>|> foo(a: R|ft<A & Any, A?>|, b: R|ft<B & Any, B?>|): R|kotlin/Unit|
+        public abstract fun <A : R|kotlin/Any!|, B : R|A!|> foo(a: R|A!|, b: R|B!|): R|kotlin/Unit|
 
     }
     public abstract interface Super : R|kotlin/Any| {
-        public abstract fun <A : R|kotlin/Any!|, B : R|ft<A & Any, A?>|> foo(a: R|ft<A & Any, A?>|, b: R|ft<B & Any, B?>|): R|kotlin/Unit|
+        public abstract fun <A : R|kotlin/Any!|, B : R|A!|> foo(a: R|A!|, b: R|B!|): R|kotlin/Unit|
 
     }
 }

compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/UseParameterInUpperBound.fir.txt

@@ -1,10 +1,10 @@
 public abstract interface UseParameterInUpperBound : R|kotlin/Any| {
     public abstract interface Sub : R|test/UseParameterInUpperBound.Super| {
-        public abstract fun <B : R|kotlin/Any!|, A : R|ft<kotlin/collections/MutableList<ft<B & Any, B?>>, kotlin/collections/List<ft<B & Any, B?>>?>|> foo(b: R|ft<B & Any, B?>|, a: R|ft<A & Any, A?>|): R|kotlin/Unit|
+        public abstract fun <B : R|kotlin/Any!|, A : R|ft<kotlin/collections/MutableList<B!>, kotlin/collections/List<B!>?>|> foo(b: R|B!|, a: R|A!|): R|kotlin/Unit|
 
     }
     public abstract interface Super : R|kotlin/Any| {
-        public abstract fun <A : R|kotlin/Any!|, B : R|ft<kotlin/collections/MutableList<ft<A & Any, A?>>, kotlin/collections/List<ft<A & Any, A?>>?>|> foo(a: R|ft<A & Any, A?>|, b: R|ft<B & Any, B?>|): R|kotlin/Unit|
+        public abstract fun <A : R|kotlin/Any!|, B : R|ft<kotlin/collections/MutableList<A!>, kotlin/collections/List<A!>?>|> foo(a: R|A!|, b: R|B!|): R|kotlin/Unit|
 
     }
 }

compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/UseParameterInUpperBoundWithKotlinSignature.fir.txt

@@ -1,10 +1,10 @@
 public abstract interface UseParameterInUpperBoundWithKotlinSignature : R|kotlin/Any| {
     public abstract interface Sub : R|test/UseParameterInUpperBoundWithKotlinSignature.Super| {
-        public abstract fun <B : R|kotlin/Any!|, A : R|ft<kotlin/collections/MutableList<ft<B & Any, B?>>, kotlin/collections/List<ft<B & Any, B?>>?>|> foo(b: R|ft<B & Any, B?>|, a: R|ft<A & Any, A?>|): R|kotlin/Unit|
+        public abstract fun <B : R|kotlin/Any!|, A : R|ft<kotlin/collections/MutableList<B!>, kotlin/collections/List<B!>?>|> foo(b: R|B!|, a: R|A!|): R|kotlin/Unit|
 
     }
     public abstract interface Super : R|kotlin/Any| {
-        public abstract fun <A : R|kotlin/Any!|, B : R|ft<kotlin/collections/MutableList<ft<A & Any, A?>>, kotlin/collections/List<ft<A & Any, A?>>?>|> foo(a: R|ft<A & Any, A?>|, b: R|ft<B & Any, B?>|): R|kotlin/Unit|
+        public abstract fun <A : R|kotlin/Any!|, B : R|ft<kotlin/collections/MutableList<A!>, kotlin/collections/List<A!>?>|> foo(a: R|A!|, b: R|B!|): R|kotlin/Unit|
 
     }
 }