[FIR] KT-46483: Forbid annotations in where Clauses

Merge-request: KT-MR-7208
Merged-by: Nikolay Lunyak <lunyak.kolya@mail.ru>

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

@@ -343,6 +343,8 @@ public interface Errors {
 
     DiagnosticFactory0<PsiElement> NON_PARENTHESIZED_ANNOTATIONS_ON_FUNCTIONAL_TYPES = DiagnosticFactory0.create(ERROR);
 
+    DiagnosticFactory0<KtAnnotationEntry> ANNOTATION_IN_WHERE_CLAUSE_WARNING = DiagnosticFactory0.create(WARNING);
+
     // Const
     DiagnosticFactory0<PsiElement> CONST_VAL_NOT_TOP_LEVEL_OR_OBJECT = DiagnosticFactory0.create(ERROR);
     DiagnosticFactory0<PsiElement> CONST_VAL_WITH_GETTER = DiagnosticFactory0.create(ERROR);

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

@@ -187,6 +187,8 @@ public class DefaultErrorMessages {
 
         MAP.put(NON_PARENTHESIZED_ANNOTATIONS_ON_FUNCTIONAL_TYPES, "Non-parenthesized annotations on function types without receiver aren't yet supported (see KT-31734 for details)");
 
+        MAP.put(ANNOTATION_IN_WHERE_CLAUSE_WARNING, "Type parameter annotations will not be allowed inside where clauses in future releases. You should probably move annotations to the type parameter declaration");
+
         MAP.put(REDUNDANT_MODIFIER, "Modifier ''{0}'' is redundant because ''{1}'' is present", TO_STRING, TO_STRING);
         MAP.put(REDUNDANT_OPEN_IN_INTERFACE, "Modifier 'open' is redundant for abstract interface members");
         MAP.put(REDUNDANT_MODIFIER_IN_GETTER, "Visibility modifiers are redundant in getter");

compiler/frontend/src/org/jetbrains/kotlin/resolve/DeclarationsChecker.kt

@@ -537,6 +537,12 @@ class DeclarationsChecker(
             checkSupertypesForConsistency(typeParameterDescriptor, typeParameter)
             checkOnlyOneTypeParameterBound(typeParameterDescriptor, typeParameter, typeParameterListOwner)
         }
+
+        for (constraint in constraints) {
+            constraint.annotationEntries.forEach {
+                trace.report(ANNOTATION_IN_WHERE_CLAUSE_WARNING.on(it))
+            }
+        }
     }
 
     private fun checkConstructorInInterface(klass: KtClass) {