Report FS3888 for generic attribute type abbreviations instead of FS0193

docs/release-notes/.FSharp.Compiler.Service/11.0.100.md

@@ -75,6 +75,7 @@
 ([PR #19724](https://github.com/dotnet/fsharp/pull/19724))
 * Emit debug points at a stack-empty position ([PR #19877](https://github.com/dotnet/fsharp/pull/19877))
 * Fix spurious XmlDoc warnings (unknown parameter / no documentation for parameter) under `--warnon:3390` when a get/set property documents the full parameter set across both accessors. ([Issue #13684](https://github.com/dotnet/fsharp/issues/13684), [PR #19884](https://github.com/dotnet/fsharp/pull/19884))
+* Replace internal compiler error FS0193 with a clear FS3888 diagnostic when a type abbreviation aliases a generic attribute type (e.g. `type B = A<int>` then `[<B>] ...`). Generic attributes remain unsupported in F#. ([Issue #7877](https://github.com/dotnet/fsharp/issues/7877), [PR #19915](https://github.com/dotnet/fsharp/pull/19915))
 
 ### Added
 

src/Compiler/Checking/Expressions/CheckExpressions.fs

@@ -11674,6 +11674,11 @@ and TcAttributeEx canFail (cenv: cenv) (env: TcEnv) attrTgt attrEx (synAttr: Syn
 
     let tcref = tcrefOfAppTy g ty
 
+    if not tcref.TyparsNoRange.IsEmpty then
+        errorR(Error(FSComp.SR.tcGenericAttributesNotSupported(tcref.DisplayName), mAttr))
+        [], false
+    else
+
     let conditionalCallDefineOpt = TryFindTyconRefStringAttribute g mAttr g.attrib_ConditionalAttribute tcref
 
     match conditionalCallDefineOpt, cenv.conditionalDefines with

src/Compiler/FSComp.txt

@@ -1818,4 +1818,5 @@ featurePreprocessorElif,"#elif preprocessor directive"
 3885,parsLetBangCannotBeLastInCE,"'%s' cannot be the final expression in a computation expression. Finish with 'return', 'return!', or a simple expression."
 3886,tcListLiteralWithSingleTupleElement,"This list expression contains a single tuple element. Did you mean to use ';' instead of ',' to separate list elements?"
 3887,ilCustomAttrInvalidArrayElemType,"The type '%s' is not a valid custom attribute argument type. Custom attribute arrays must have elements of primitive types, enums, string, System.Type, or System.Object."
+3888,tcGenericAttributesNotSupported,"Generic attribute types are not supported in F#. The type '%s' has type parameters and cannot be used as an attribute."
 featureExceptionFieldSerializationSupport,"emit GetObjectData and field-restoring deserialization constructor for exception types"