Add parser recovery for unfinished interface implementation (dotnet#10416)

* Add parser recovery for unfinished interface implementation

* Report indentation problem via parser

* Update public area

Author: auduchinok

src/fsharp/LexFilter.fs

@@ -22,7 +22,7 @@ let outputPos os (p: Position) = Printf.fprintf os "(%d:%d)" p.OriginalLine p.Co
 /// Used for warning strings, which should display columns as 1-based and display 
 /// the lines after taking '# line' directives into account (i.e. do not use
 /// p.OriginalLine)
-let warningStringOfPos (p: Position) = sprintf "(%d:%d)" p.Line (p.Column + 1)
+let warningStringOfPosition (p: Position) = warningStringOfCoords p.Line p.Column
 
 type Context = 
     // Position is position of keyword.
@@ -651,7 +651,7 @@ type LexFilterImpl (lightStatus: LightSyntaxStatus, compilingFsLib, lexer, lexbu
         initialLookaheadTokenTup 
 
     let warn (s: TokenTup) msg = 
-        warning(Lexhelp.IndentationProblem(msg, mkSynRange (startPosOfTokenTup s) s.LexbufState.EndPos))
+        warning(IndentationProblem(msg, mkSynRange (startPosOfTokenTup s) s.LexbufState.EndPos))
 
     // 'query { join x in ys ... }'
     // 'query { ... 
@@ -865,9 +865,9 @@ type LexFilterImpl (lightStatus: LightSyntaxStatus, compilingFsLib, lexer, lexbu
                 warn tokenTup 
                     (if debug then 
                         sprintf "possible incorrect indentation: this token is offside of context at position %s, newCtxt = %A, stack = %A, newCtxtPos = %s, c1 = %d, c2 = %d" 
-                            (warningStringOfPos p1.Position) newCtxt offsideStack (stringOfPos (newCtxt.StartPos)) p1.Column c2 
+                            (warningStringOfPosition p1.Position) newCtxt offsideStack (stringOfPos (newCtxt.StartPos)) p1.Column c2 
                      else
-                        FSComp.SR.lexfltTokenIsOffsideOfContextStartedEarlier(warningStringOfPos p1.Position))
+                        FSComp.SR.lexfltTokenIsOffsideOfContextStartedEarlier(warningStringOfPosition p1.Position))
         let newOffsideStack = newCtxt :: offsideStack
         if debug then dprintf "--> pushing, stack = %A\n" newOffsideStack
         offsideStack <- newOffsideStack
@@ -1749,7 +1749,7 @@ type LexFilterImpl (lightStatus: LightSyntaxStatus, compilingFsLib, lexer, lexbu
                                 let cond1 = tokenStartCol + (if leadingBar then 0 else 2) < offsidePos.Column
                                 let cond2 = tokenStartCol + (if leadingBar then 1 else 2) < offsidePos.Column
                                 if (cond1 <> cond2) then 
-                                    errorR(Lexhelp.IndentationProblem(FSComp.SR.lexfltSeparatorTokensOfPatternMatchMisaligned(), mkSynRange (startPosOfTokenTup tokenTup) tokenTup.LexbufState.EndPos))
+                                    errorR(IndentationProblem(FSComp.SR.lexfltSeparatorTokensOfPatternMatchMisaligned(), mkSynRange (startPosOfTokenTup tokenTup) tokenTup.LexbufState.EndPos))
                                 cond1
                             | END -> tokenStartCol + (if leadingBar then -1 else 1) < offsidePos.Column
                             | _ -> tokenStartCol + (if leadingBar then -1 else 1) < offsidePos.Column)) -> 
@@ -2066,6 +2066,11 @@ type LexFilterImpl (lightStatus: LightSyntaxStatus, compilingFsLib, lexer, lexbu
                     let offsidePos = tokenStartPos
                     pushCtxt tokenTup (CtxtWithAsLet offsidePos)
                     returnToken tokenLexbufState OWITH 
+
+                // Recovery for `interface ... with` member without further indented member implementations
+                elif lookaheadTokenStartPos.Column <= limCtxt.StartCol && (match limCtxt with CtxtInterfaceHead _ -> true | _ -> false) then
+                    returnToken tokenLexbufState token
+
                 else
                     // In these situations
                     //    interface I with 

src/fsharp/ParseHelpers.fs

@@ -23,6 +23,14 @@ open Internal.Utilities.Text.Parsing
 [<NoEquality; NoComparison>]
 exception SyntaxError of obj (* ParseErrorContext<_> *) * range: range
 
+exception IndentationProblem of string * range
+
+let warningStringOfCoords line column =
+    sprintf "(%d:%d)" line (column + 1)
+
+let warningStringOfPos (p: pos) =
+    warningStringOfCoords p.Line p.Column
+
 //------------------------------------------------------------------------
 // Parsing: getting positions from the lexer
 //------------------------------------------------------------------------

src/fsharp/lexhelp.fs

@@ -230,7 +230,6 @@ let escape c =
 //-----------------------------------------------------------------------   
 
 exception ReservedKeyword of string * range
-exception IndentationProblem of string * range
 
 module Keywords = 
     type private compatibilityMode =

src/fsharp/lexhelp.fsi

@@ -93,8 +93,6 @@ val escape: char -> char
 
 exception ReservedKeyword of string * Range.range
 
-exception IndentationProblem of string * Range.range
-
 module Keywords = 
 
     val KeywordOrIdentifierToken: LexArgs -> UnicodeLexing.Lexbuf -> string -> token

src/fsharp/pars.fsy

@@ -1649,9 +1649,13 @@ classDefnMembers:
 
 
 /* The members of an object type definition or type augmentation */
-classDefnMembersAtLeastOne:  
-  | classDefnMember opt_seps classDefnMembers 
-     { $1 @  $3 }
+classDefnMembersAtLeastOne:
+  | classDefnMember opt_seps classDefnMembers
+     { match $1, $3 with
+       | [ SynMemberDefn.Interface (_, Some [], m) ], nextMember :: _ ->
+           warning(IndentationProblem(FSComp.SR.lexfltTokenIsOffsideOfContextStartedEarlier(warningStringOfPos m.Start), nextMember.Range))
+       | _ -> ()
+       $1 @ $3 }
 
 
 /* The "with get, set" part of a member definition */
@@ -1904,11 +1908,12 @@ classDefnMember:
   | opt_attributes opt_declVisibility interfaceMember appType opt_interfaceImplDefn  
      {  if not (isNil $1) then errorR(Error(FSComp.SR.parsAttributesAreNotPermittedOnInterfaceImplementations(), rhs parseState 1))
         if Option.isSome $2 then errorR(Error(FSComp.SR.parsInterfacesHaveSameVisibilityAsEnclosingType(), rhs parseState 3))
-        let mWhole = 
+        let members = Option.map fst $5
+        let mWhole =
             match $5 with
             | None -> rhs2 parseState 1 4
-            | Some(mems) -> (rhs2 parseState 1 4, mems) ||> unionRangeWithListBy (fun (mem:SynMemberDefn) -> mem.Range)
-        [ SynMemberDefn.Interface ($4, $5, mWhole) ] }
+            | Some (_, m) -> unionRanges (rhs2 parseState 1 4) m
+        [ SynMemberDefn.Interface ($4, members, mWhole) ] }
 
   | opt_attributes opt_declVisibility abstractMemberFlags opt_inline nameop opt_explicitValTyparDecls COLON topTypeWithTypeConstraints classMemberSpfnGetSet  opt_ODECLEND
      { let ty, arity = $8
@@ -2042,9 +2047,14 @@ opt_declVisibility:
      { None }
 
 
-opt_interfaceImplDefn: 
+opt_interfaceImplDefn:
   | WITH objectImplementationBlock declEnd
-     { Some($2) } 
+     { let members = $2
+       let m = (rhs parseState 1, members) ||> unionRangeWithListBy (fun (mem:SynMemberDefn) -> mem.Range)
+       Some (members, m) }
+
+  | WITH
+     { Some ([], rhs parseState 1) }
 
   | /* EMPTY */
      { None }

tests/FSharp.Compiler.Service.Tests/FSharp.Compiler.Service.Tests.fsproj

@@ -67,6 +67,9 @@
     <Compile Include="..\service\ScriptOptionsTests.fs">
       <Link>ScriptOptionsTests.fs</Link>
     </Compile>
+    <Compile Include="..\service\ParserTests.fs" >
+      <Link>ParserTests.fs</Link>
+    </Compile>
     <Compile Include="..\service\Program.fs">
       <Link>Program.fs</Link>
     </Compile>

tests/FSharp.Compiler.Service.Tests/SurfaceArea.netstandard.fs

@@ -20020,6 +20020,20 @@ FSharp.Compiler.ParseHelpers: FSharp.Compiler.ParseHelpers+LexerStringStyle
 FSharp.Compiler.ParseHelpers: FSharp.Compiler.ParseHelpers+SyntaxError
 FSharp.Compiler.ParseHelpers: ILInstr[] ParseAssemblyCodeInstructions(System.String, range)
 FSharp.Compiler.ParseHelpers: ILType ParseAssemblyCodeType(System.String, range)
+FSharp.Compiler.ParseHelpers+IndentationProblem: Boolean Equals(System.Exception)
+FSharp.Compiler.ParseHelpers+IndentationProblem: Boolean Equals(System.Object)
+FSharp.Compiler.ParseHelpers+IndentationProblem: Boolean Equals(System.Object, System.Collections.IEqualityComparer)
+FSharp.Compiler.ParseHelpers+IndentationProblem: Int32 GetHashCode()
+FSharp.Compiler.ParseHelpers+IndentationProblem: Int32 GetHashCode(System.Collections.IEqualityComparer)
+FSharp.Compiler.ParseHelpers+IndentationProblem: System.String Data0
+FSharp.Compiler.ParseHelpers+IndentationProblem: System.String get_Data0()
+FSharp.Compiler.ParseHelpers+IndentationProblem: Void .ctor()
+FSharp.Compiler.ParseHelpers+IndentationProblem: Void .ctor(System.String, range)
+FSharp.Compiler.ParseHelpers+IndentationProblem: range Data1
+FSharp.Compiler.ParseHelpers+IndentationProblem: range get_Data1()
+FSharp.Compiler.ParseHelpers: FSharp.Compiler.ParseHelpers+IndentationProblem
+FSharp.Compiler.ParseHelpers: System.String warningStringOfCoords(Int32, Int32)
+FSharp.Compiler.ParseHelpers: System.String warningStringOfPos(pos)
 FSharp.Compiler.PartialLongName: Boolean Equals(FSharp.Compiler.PartialLongName)
 FSharp.Compiler.PartialLongName: Boolean Equals(System.Object)
 FSharp.Compiler.PartialLongName: Boolean Equals(System.Object, System.Collections.IEqualityComparer)

tests/service/Common.fs

@@ -337,9 +337,14 @@ let rec allSymbolsInEntities compGen (entities: IList<FSharpEntity>) =
                  yield (x :> FSharpSymbol)
           yield! allSymbolsInEntities compGen e.NestedEntities ]
 
+
+let getParseResults (source: string) =
+    parseSourceCode("/home/user/Test.fsx", source)
+
 let getParseAndCheckResults (source: string) =
     parseAndCheckScript("/home/user/Test.fsx", source)
 
+
 let inline dumpErrors results =
     (^TResults: (member Errors: FSharpErrorInfo[]) results)
     |> Array.map (fun e ->

tests/service/ParserTests.fs

@@ -0,0 +1,21 @@
+module Tests.Parser
+
+open FSharp.Compiler.Service.Tests.Common
+open FSharp.Compiler.SyntaxTree
+open NUnit.Framework
+
+module Recovery =
+    [<Test>]
+    let ``Unfinished interface member`` () =
+        let parseResults = getParseResults """
+type T =
+    interface I with
+    member x.P2 = ()
+
+let x = ()
+"""
+        let (SynModuleOrNamespace (decls = decls)) = getSingleModuleLikeDecl parseResults
+        match decls with
+        | [ SynModuleDecl.Types ([ TypeDefn (typeRepr = SynTypeDefnRepr.ObjectModel (members = [ _; _ ])) ], _)
+            SynModuleDecl.Let _ ] -> ()
+        | _ -> failwith "Unexpected tree"