RFC FS-1124 - Interfaces with static abstract methods (#13119)

Co-authored-by: Don Syme <dsyme@users.noreply.github.com>
Co-authored-by: Don Syme <donsyme@fastmail.fm>
Co-authored-by: Petr Pokorny <petrpokorny@microsoft.com>

.vscode/launch.json

@@ -23,7 +23,7 @@
             "internalConsoleOptions": "neverOpen",
             "suppressJITOptimizations": true,
             "stopAtEntry": false,
-            "justMyCode": false,
+            "justMyCode": true,
             "enableStepFiltering": true,
             "symbolOptions": {
                 "searchMicrosoftSymbolServer": true,
@@ -73,7 +73,7 @@
                     "enabled": true
                 }
             },
-            "justMyCode": false,
+            "justMyCode": true,
             "enableStepFiltering": false,
         }
     ]

src/Compiler/AbstractIL/il.fs

@@ -1370,7 +1370,7 @@ type ILInstr =
 
     | I_call of ILTailcall * ILMethodSpec * ILVarArgs
     | I_callvirt of ILTailcall * ILMethodSpec * ILVarArgs
-    | I_callconstraint of ILTailcall * ILType * ILMethodSpec * ILVarArgs
+    | I_callconstraint of callvirt: bool * ILTailcall * ILType * ILMethodSpec * ILVarArgs
     | I_calli of ILTailcall * ILCallingSignature * ILVarArgs
     | I_ldftn of ILMethodSpec
     | I_newobj of ILMethodSpec * ILVarArgs
@@ -3410,9 +3410,6 @@ let mkNormalCall mspec = I_call(Normalcall, mspec, None)
 
 let mkNormalCallvirt mspec = I_callvirt(Normalcall, mspec, None)
 
-let mkNormalCallconstraint (ty, mspec) =
-    I_callconstraint(Normalcall, ty, mspec, None)
-
 let mkNormalNewobj mspec = I_newobj(mspec, None)
 
 /// Comment on common object cache sizes:
@@ -3822,18 +3819,24 @@ let mkILClassCtor impl =
 let mk_ospec (ty: ILType, callconv, nm, genparams, formal_args, formal_ret) =
     OverridesSpec(mkILMethRef (ty.TypeRef, callconv, nm, genparams, formal_args, formal_ret), ty)
 
-let mkILGenericVirtualMethod (nm, access, genparams, actual_args, actual_ret, impl) =
+let mkILGenericVirtualMethod (nm, callconv: ILCallingConv, access, genparams, actual_args, actual_ret, impl) =
+    let attributes =
+        convertMemberAccess access
+        ||| MethodAttributes.CheckAccessOnOverride
+        ||| (match impl with
+             | MethodBody.Abstract -> MethodAttributes.Abstract ||| MethodAttributes.Virtual
+             | _ -> MethodAttributes.Virtual)
+        ||| (if callconv.IsInstance then
+                 enum 0
+             else
+                 MethodAttributes.Static)
+
     ILMethodDef(
         name = nm,
-        attributes =
-            (convertMemberAccess access
-             ||| MethodAttributes.CheckAccessOnOverride
-             ||| (match impl with
-                  | MethodBody.Abstract -> MethodAttributes.Abstract ||| MethodAttributes.Virtual
-                  | _ -> MethodAttributes.Virtual)),
+        attributes = attributes,
         implAttributes = MethodImplAttributes.Managed,
         genericParams = genparams,
-        callingConv = ILCallingConv.Instance,
+        callingConv = callconv,
         parameters = actual_args,
         ret = actual_ret,
         isEntryPoint = false,
@@ -3842,8 +3845,11 @@ let mkILGenericVirtualMethod (nm, access, genparams, actual_args, actual_ret, im
         body = notlazy impl
     )
 
-let mkILNonGenericVirtualMethod (nm, access, args, ret, impl) =
-    mkILGenericVirtualMethod (nm, access, mkILEmptyGenericParams, args, ret, impl)
+let mkILNonGenericVirtualMethod (nm, callconv, access, args, ret, impl) =
+    mkILGenericVirtualMethod (nm, callconv, access, mkILEmptyGenericParams, args, ret, impl)
+
+let mkILNonGenericVirtualInstanceMethod (nm, access, args, ret, impl) =
+    mkILNonGenericVirtualMethod (nm, ILCallingConv.Instance, access, args, ret, impl)
 
 let mkILGenericNonVirtualMethod (nm, access, genparams, actual_args, actual_ret, impl) =
     ILMethodDef(
@@ -4267,7 +4273,7 @@ let mkILDelegateMethods access (ilg: ILGlobals) (iltyp_AsyncCallback, iltyp_IAsy
 
     let one nm args ret =
         let mdef =
-            mkILNonGenericVirtualMethod (nm, access, args, mkILReturn ret, MethodBody.Abstract)
+            mkILNonGenericVirtualInstanceMethod (nm, access, args, mkILReturn ret, MethodBody.Abstract)
 
         mdef.WithAbstract(false).WithHideBySig(true).WithRuntime(true)
 
@@ -5298,7 +5304,7 @@ and refsOfILInstr s x =
     | I_callvirt (_, mr, varargs) ->
         refsOfILMethodSpec s mr
         refsOfILVarArgs s varargs
-    | I_callconstraint (_, tr, mr, varargs) ->
+    | I_callconstraint (_, _, tr, mr, varargs) ->
         refsOfILType s tr
         refsOfILMethodSpec s mr
         refsOfILVarArgs s varargs

src/Compiler/AbstractIL/il.fsi

@@ -523,7 +523,7 @@ type internal ILInstr =
     // Method call
     | I_call of ILTailcall * ILMethodSpec * ILVarArgs
     | I_callvirt of ILTailcall * ILMethodSpec * ILVarArgs
-    | I_callconstraint of ILTailcall * ILType * ILMethodSpec * ILVarArgs
+    | I_callconstraint of callvirt: bool * ILTailcall * ILType * ILMethodSpec * ILVarArgs
     | I_calli of ILTailcall * ILCallingSignature * ILVarArgs
     | I_ldftn of ILMethodSpec
     | I_newobj of ILMethodSpec * ILVarArgs
@@ -1970,7 +1970,6 @@ type internal ILLocalsAllocator =
 /// Derived functions for making some common patterns of instructions.
 val internal mkNormalCall: ILMethodSpec -> ILInstr
 val internal mkNormalCallvirt: ILMethodSpec -> ILInstr
-val internal mkNormalCallconstraint: ILType * ILMethodSpec -> ILInstr
 val internal mkNormalNewobj: ILMethodSpec -> ILInstr
 val internal mkCallBaseConstructor: ILType * ILType list -> ILInstr list
 val internal mkNormalStfld: ILFieldSpec -> ILInstr
@@ -2025,12 +2024,16 @@ val internal mkILNonGenericStaticMethod:
     string * ILMemberAccess * ILParameter list * ILReturn * MethodBody -> ILMethodDef
 
 val internal mkILGenericVirtualMethod:
-    string * ILMemberAccess * ILGenericParameterDefs * ILParameter list * ILReturn * MethodBody -> ILMethodDef
+    string * ILCallingConv * ILMemberAccess * ILGenericParameterDefs * ILParameter list * ILReturn * MethodBody ->
+        ILMethodDef
 
 val internal mkILGenericNonVirtualMethod:
     string * ILMemberAccess * ILGenericParameterDefs * ILParameter list * ILReturn * MethodBody -> ILMethodDef
 
 val internal mkILNonGenericVirtualMethod:
+    string * ILCallingConv * ILMemberAccess * ILParameter list * ILReturn * MethodBody -> ILMethodDef
+
+val internal mkILNonGenericVirtualInstanceMethod:
     string * ILMemberAccess * ILParameter list * ILReturn * MethodBody -> ILMethodDef
 
 val internal mkILNonGenericInstanceMethod:

src/Compiler/AbstractIL/ilmorph.fs

@@ -212,7 +212,8 @@ let morphILTypesInILInstr ((factualTy, fformalTy)) i =
     | I_calli (a, mref, varargs) -> I_calli(a, callsig_ty2ty factualTy mref, morphILVarArgs factualTy varargs)
     | I_call (a, mr, varargs) -> I_call(a, conv_mspec mr, morphILVarArgs factualTy varargs)
     | I_callvirt (a, mr, varargs) -> I_callvirt(a, conv_mspec mr, morphILVarArgs factualTy varargs)
-    | I_callconstraint (a, ty, mr, varargs) -> I_callconstraint(a, factualTy ty, conv_mspec mr, morphILVarArgs factualTy varargs)
+    | I_callconstraint (callvirt, a, ty, mr, varargs) ->
+        I_callconstraint(callvirt, a, factualTy ty, conv_mspec mr, morphILVarArgs factualTy varargs)
     | I_newobj (mr, varargs) -> I_newobj(conv_mspec mr, morphILVarArgs factualTy varargs)
     | I_ldftn mr -> I_ldftn(conv_mspec mr)
     | I_ldvirtftn mr -> I_ldvirtftn(conv_mspec mr)

src/Compiler/AbstractIL/ilprint.fs

@@ -893,11 +893,11 @@ let rec goutput_instr env os inst =
         output_string os "callvirt "
         goutput_vararg_mspec env os (mspec, varargs)
         output_after_tailcall os tl
-    | I_callconstraint (tl, ty, mspec, varargs) ->
+    | I_callconstraint (callvirt, tl, ty, mspec, varargs) ->
         output_tailness os tl
         output_string os "constraint. "
         goutput_typ env os ty
-        output_string os " callvirt "
+        output_string os (if callvirt then " callvirt " else " call ")
         goutput_vararg_mspec env os (mspec, varargs)
         output_after_tailcall os tl
     | I_castclass ty ->

src/Compiler/AbstractIL/ilread.fs

@@ -626,17 +626,23 @@ let instrs () =
         i_stsfld, I_field_instr(volatilePrefix (fun x fspec -> I_stsfld(x, fspec)))
         i_ldflda, I_field_instr(noPrefixes I_ldflda)
         i_ldsflda, I_field_instr(noPrefixes I_ldsflda)
-        i_call, I_method_instr(tailPrefix (fun tl (mspec, y) -> I_call(tl, mspec, y)))
+        (i_call,
+         I_method_instr(
+             constraintOrTailPrefix (fun (c, tl) (mspec, y) ->
+                 match c with
+                 | Some ty -> I_callconstraint(false, tl, ty, mspec, y)
+                 | None -> I_call(tl, mspec, y))
+         ))
         i_ldftn, I_method_instr(noPrefixes (fun (mspec, _y) -> I_ldftn mspec))
         i_ldvirtftn, I_method_instr(noPrefixes (fun (mspec, _y) -> I_ldvirtftn mspec))
         i_newobj, I_method_instr(noPrefixes I_newobj)
-        i_callvirt,
-        I_method_instr(
-            constraintOrTailPrefix (fun (c, tl) (mspec, y) ->
-                match c with
-                | Some ty -> I_callconstraint(tl, ty, mspec, y)
-                | None -> I_callvirt(tl, mspec, y))
-        )
+        (i_callvirt,
+         I_method_instr(
+             constraintOrTailPrefix (fun (c, tl) (mspec, y) ->
+                 match c with
+                 | Some ty -> I_callconstraint(true, tl, ty, mspec, y)
+                 | None -> I_callvirt(tl, mspec, y))
+         ))
         i_leave_s, I_unconditional_i8_instr(noPrefixes (fun x -> I_leave x))
         i_br_s, I_unconditional_i8_instr(noPrefixes I_br)
         i_leave, I_unconditional_i32_instr(noPrefixes (fun x -> I_leave x))

src/Compiler/AbstractIL/ilreflect.fs

@@ -1391,9 +1391,10 @@ let rec emitInstr cenv (modB: ModuleBuilder) emEnv (ilG: ILGenerator) instr =
         emitSilverlightCheck ilG
         emitInstrCall cenv emEnv ilG OpCodes.Callvirt tail mspec varargs
 
-    | I_callconstraint (tail, ty, mspec, varargs) ->
+    | I_callconstraint (callvirt, tail, ty, mspec, varargs) ->
         ilG.Emit(OpCodes.Constrained, convType cenv emEnv ty)
-        emitInstrCall cenv emEnv ilG OpCodes.Callvirt tail mspec varargs
+        let instr = if callvirt then OpCodes.Callvirt else OpCodes.Call
+        emitInstrCall cenv emEnv ilG instr tail mspec varargs
 
     | I_calli (tail, callsig, None) ->
         emitInstrTail cenv ilG tail (fun () ->

src/Compiler/AbstractIL/ilwrite.fs

@@ -1922,10 +1922,11 @@ module Codebuf =
             emitTailness cenv codebuf tl
             emitMethodSpecInstr cenv codebuf env i_callvirt (mspec, varargs)
             //emitAfterTailcall codebuf tl
-        | I_callconstraint (tl, ty, mspec, varargs) ->
+        | I_callconstraint (callvirt, tl, ty, mspec, varargs) ->
             emitTailness cenv codebuf tl
             emitConstrained cenv codebuf env ty
-            emitMethodSpecInstr cenv codebuf env i_callvirt (mspec, varargs)
+            let instr = if callvirt then i_callvirt else i_call
+            emitMethodSpecInstr cenv codebuf env instr (mspec, varargs)
             //emitAfterTailcall codebuf tl
         | I_newobj (mspec, varargs) ->
             emitMethodSpecInstr cenv codebuf env i_newobj (mspec, varargs)

src/Compiler/Checking/CheckComputationExpressions.fs

@@ -468,7 +468,7 @@ let TcComputationExpression (cenv: cenv) env (overallTy: OverallTy) tpenv (mWhol
                         match info with 
                         | None -> false
                         | Some args -> 
-                            args |> List.exists (fun (isParamArrayArg, _isInArg, isOutArg, optArgInfo, _callerInfo, _reflArgInfo) -> isParamArrayArg || isOutArg || optArgInfo.IsOptional))
+                            args |> List.exists (fun (ParamAttribs(isParamArrayArg, _isInArg, isOutArg, optArgInfo, _callerInfo, _reflArgInfo)) -> isParamArrayArg || isOutArg || optArgInfo.IsOptional))
                 else
                     false