FIR checker: report non-typed LHS of callable references

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/diagnostics/FirDiagnostics.kt

@@ -82,6 +82,10 @@ class ConeTypeParameterSupertype(val symbol: FirTypeParameterSymbol) : ConeDiagn
     override val reason: String get() = "Type parameter ${symbol.fir.name} cannot be a supertype"
 }
 
+class ConeTypeParameterInQualifiedAccess(val symbol: FirTypeParameterSymbol) : ConeDiagnostic() {
+    override val reason: String get() = "Type parameter ${symbol.fir.name} in qualified access"
+}
+
 private fun describeSymbol(symbol: AbstractFirBasedSymbol<*>): String {
     return when (symbol) {
         is FirClassLikeSymbol<*> -> symbol.classId.asString()

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/FirCallCompletionResultsWriterTransformer.kt

@@ -17,6 +17,7 @@ import org.jetbrains.kotlin.fir.references.builder.buildResolvedNamedReference
 import org.jetbrains.kotlin.fir.resolve.*
 import org.jetbrains.kotlin.fir.resolve.calls.*
 import org.jetbrains.kotlin.fir.resolve.dfa.FirDataFlowAnalyzer
+import org.jetbrains.kotlin.fir.resolve.diagnostics.ConeTypeParameterInQualifiedAccess
 import org.jetbrains.kotlin.fir.resolve.inference.*
 import org.jetbrains.kotlin.fir.resolve.substitution.ConeSubstitutor
 import org.jetbrains.kotlin.fir.resolve.transformers.body.resolve.FirArrayOfCallTransformer
@@ -89,11 +90,14 @@ class FirCallCompletionResultsWriterTransformer(
             // e.g. `T::toString` where T is a generic type.
             // in these cases we should report an error on
             // the calleeReference.source which is not a fake source.
-            // uncommenting `?.fakeElement...` here removes reports
-            // of OTHER_ERROR from tests.
             buildErrorTypeRef {
-                source = calleeReference.source //?.fakeElement(FirFakeSourceElementKind.ImplicitTypeRef)
-                diagnostic = ConeSimpleDiagnostic("Callee reference to candidate without return type: ${declaration.render()}")
+                source = calleeReference.source?.fakeElement(FirFakeSourceElementKind.ImplicitTypeRef)
+                diagnostic =
+                    when (declaration) {
+                        is FirTypeParameter -> ConeTypeParameterInQualifiedAccess(declaration.symbol)
+                        is FirResolvedReifiedParameterReference -> ConeTypeParameterInQualifiedAccess(declaration.symbol)
+                        else -> ConeSimpleDiagnostic("Callee reference to candidate without return type: ${declaration.render()}")
+                    }
             }
         }