[FE 1.0] Introduce deprecation of inferred type variable into a declared upper bound within a builder inference call

compiler/frontend/src/org/jetbrains/kotlin/diagnostics/Errors.java

@@ -890,6 +890,7 @@ public interface Errors {
 
     DiagnosticFactory1<PsiElement, InferenceErrorData> TYPE_INFERENCE_NO_INFORMATION_FOR_PARAMETER = DiagnosticFactory1.create(ERROR);
     DiagnosticFactory1<PsiElement, String> NEW_INFERENCE_NO_INFORMATION_FOR_PARAMETER = DiagnosticFactory1.create(ERROR);
+    DiagnosticFactory1<PsiElement, String> INFERRED_INTO_DECLARED_UPPER_BOUNDS = DiagnosticFactory1.create(WARNING);
     DiagnosticFactory1<PsiElement, String> COULD_BE_INFERRED_ONLY_WITH_UNRESTRICTED_BUILDER_INFERENCE = DiagnosticFactory1.create(ERROR);
 
     DiagnosticFactory1<PsiElement, InferenceErrorData> TYPE_INFERENCE_CONFLICTING_SUBSTITUTIONS = DiagnosticFactory1.create(ERROR);

compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/DefaultErrorMessages.java

@@ -959,6 +959,8 @@ public class DefaultErrorMessages {
         MAP.put(TYPE_INFERENCE_CANNOT_CAPTURE_TYPES, "Type inference failed: {0}", TYPE_INFERENCE_CANNOT_CAPTURE_TYPES_RENDERER);
         MAP.put(TYPE_INFERENCE_NO_INFORMATION_FOR_PARAMETER, "Type inference failed: {0}", TYPE_INFERENCE_NO_INFORMATION_FOR_PARAMETER_RENDERER);
         MAP.put(NEW_INFERENCE_NO_INFORMATION_FOR_PARAMETER, "Not enough information to infer type variable {0}", STRING);
+        MAP.put(INFERRED_INTO_DECLARED_UPPER_BOUNDS, "Type parameter for a type argument {0} can''t be inferred into declared upper bounds. " +
+                                                     "Please provide any use-site type information. It will become an error in future releases.", STRING);
         MAP.put(COULD_BE_INFERRED_ONLY_WITH_UNRESTRICTED_BUILDER_INFERENCE, "Builder inference lambda contains inapplicable calls so {0} can''t be inferred. It could be resolved only with unrestricted builder inference. Please use -Xunrestricted-builder-inference compiler flag to enable it.", STRING);
 
         MAP.put(TYPE_INFERENCE_PARAMETER_CONSTRAINT_ERROR, "Type inference failed: {0}", TYPE_INFERENCE_PARAMETER_CONSTRAINT_ERROR_RENDERER);

compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/DiagnosticReporterByTrackingStrategy.kt

@@ -541,6 +541,22 @@ class DiagnosticReporterByTrackingStrategy(
                 }
             }
 
+            InferredIntoDeclaredUpperBounds::class.java -> {
+                error as InferredIntoDeclaredUpperBounds
+
+                val psiCall = psiKotlinCall.psiCall
+                val expression = if (psiCall is CallTransformer.CallForImplicitInvoke) {
+                    psiCall.outerCall.calleeExpression
+                } else {
+                    psiCall.calleeExpression
+                } ?: return
+                val typeVariable = error.typeVariable as? TypeVariableFromCallableDescriptor ?: return
+
+                trace.reportDiagnosticOnce(
+                    INFERRED_INTO_DECLARED_UPPER_BOUNDS.on(expression, typeVariable.originalTypeParameter.name.asString())
+                )
+            }
+
             NotEnoughInformationForTypeParameterImpl::class.java -> {
                 error as NotEnoughInformationForTypeParameterImpl
 

compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/inference/BuilderInferenceSession.kt

@@ -6,6 +6,7 @@
 package org.jetbrains.kotlin.resolve.calls.inference
 
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns
+import org.jetbrains.kotlin.config.LanguageFeature
 import org.jetbrains.kotlin.descriptors.CallableDescriptor
 import org.jetbrains.kotlin.descriptors.ModuleDescriptor
 import org.jetbrains.kotlin.descriptors.impl.AnonymousFunctionDescriptor
@@ -34,7 +35,6 @@ import org.jetbrains.kotlin.types.*
 import org.jetbrains.kotlin.types.checker.NewCapturedType
 import org.jetbrains.kotlin.types.expressions.DoubleColonExpressionResolver
 import org.jetbrains.kotlin.types.expressions.ExpressionTypingServices
-import org.jetbrains.kotlin.types.model.freshTypeConstructor
 import org.jetbrains.kotlin.types.model.safeSubstitute
 import org.jetbrains.kotlin.types.typeUtil.asTypeProjection
 import org.jetbrains.kotlin.types.typeUtil.contains
@@ -589,10 +589,15 @@ class BuilderInferenceSession(
 
         if (lowerSubstituted == a && upperSubstituted == b) return this
 
-        val resultingPosition = if (upperSubstituted == b && position is DeclaredUpperBoundConstraintPosition<*>) {
+        val isInferringIntoUpperBoundsForbidden = expressionTypingServices.languageVersionSettings.supportsFeature(
+            LanguageFeature.ForbidInferringPostponedTypeVariableIntoDeclaredUpperBound
+        )
+        val isFromNotSubstitutedDeclaredUpperBound = upperSubstituted == b && position is DeclaredUpperBoundConstraintPosition<*>
+
+        val resultingPosition = if (isFromNotSubstitutedDeclaredUpperBound && isInferringIntoUpperBoundsForbidden) {
             position
         } else {
-            BuilderInferenceSubstitutionConstraintPositionImpl(lambdaArgument, this)
+            BuilderInferenceSubstitutionConstraintPositionImpl(lambdaArgument, this, isFromNotSubstitutedDeclaredUpperBound)
         }
 
         return InitialConstraint(