Parser: fix tree for missing item in top tuple type (#15909)

src/Compiler/SyntaxTree/SyntaxTreeOps.fs

@@ -663,6 +663,8 @@ module SynInfo =
 
     let emptySynValData = SynValData(None, emptySynValInfo, None, None)
 
+    let emptySynArgInfo = SynArgInfo([], false, None)
+
     /// Infer the syntactic information for a 'let' or 'member' definition, based on the argument pattern,
     /// any declared return information (e.g. .NET attributes on the return element), and the r.h.s. expression
     /// in the case of 'let' definitions.

src/Compiler/SyntaxTree/SyntaxTreeOps.fsi

@@ -257,6 +257,8 @@ module SynInfo =
 
     val emptySynValData: SynValData
 
+    val emptySynArgInfo: SynArgInfo
+
     /// Infer the syntactic information for a 'let' or 'member' definition, based on the argument pattern,
     /// any declared return information (e.g. .NET attributes on the return element), and the r.h.s. expression
     /// in the case of 'let' definitions.

src/Compiler/pars.fsy

@@ -5690,7 +5690,7 @@ topTupleType:
        let mStar = rhs parseState 2
        let ty2 = SynType.FromParseError(mStar.EndRange)
        let path = [SynTupleTypeSegment.Type ty1; SynTupleTypeSegment.Star mStar; SynTupleTypeSegment.Type ty2]
-       mkSynTypeTuple path, [argInfo] }
+       mkSynTypeTuple path, [argInfo; SynInfo.emptySynArgInfo] }
 
   | STAR topTupleTypeElements
       { let mStar = rhs parseState 1
@@ -5713,7 +5713,7 @@ topTupleTypeElements:
       { let ty1, argInfo = $1
         let mStar = rhs parseState 2
         let ty2 = SynType.FromParseError(mStar.EndRange)
-        [(SynTupleTypeSegment.Type ty1, Some argInfo); (SynTupleTypeSegment.Star mStar, None); (SynTupleTypeSegment.Type ty2, None)] }
+        [SynTupleTypeSegment.Type ty1, Some argInfo; SynTupleTypeSegment.Star mStar, None; SynTupleTypeSegment.Type ty2, Some SynInfo.emptySynArgInfo] }
 
   | STAR topTupleTypeElements
       { let mStar = rhs parseState 1

tests/service/data/SyntaxTree/ModuleMember/Val 01.fsi

+module Module
+
+val f: int * -> unit

tests/service/data/SyntaxTree/ModuleMember/Val 01.fsi.bsl

+SigFile
+  (ParsedSigFileInput
+     ("/root/ModuleMember/Val 01.fsi", QualifiedNameOfFile Module, [], [],
+      [SynModuleOrNamespaceSig
+         ([Module], false, NamedModule,
+          [Val
+             (SynValSig
+                ([], SynIdent (f, None), SynValTyparDecls (None, true),
+                 Fun
+                   (Tuple
+                      (false,
+                       [Type (LongIdent (SynLongIdent ([int], [], [None])));
+                        Star (3,11--3,12); Type (FromParseError (3,12--3,12))],
+                       (3,7--3,12)),
+                    LongIdent (SynLongIdent ([unit], [], [None])), (3,7--3,20),
+                    { ArrowRange = (3,13--3,15) }),
+                 SynValInfo
+                   ([[SynArgInfo ([], false, None); SynArgInfo ([], false, None)]],
+                    SynArgInfo ([], false, None)), false, false,
+                 PreXmlDoc ((3,0), FSharp.Compiler.Xml.XmlDocCollector), None,
+                 None, (3,0--3,20), { LeadingKeyword = Val (3,0--3,3)
+                                      InlineKeyword = None
+                                      WithKeyword = None
+                                      EqualsRange = None }), (3,0--3,20))],
+          PreXmlDoc ((1,0), FSharp.Compiler.Xml.XmlDocCollector), [], None,
+          (1,0--3,20), { LeadingKeyword = Module (1,0--1,6) })],
+      { ConditionalDirectives = []
+        CodeComments = [] }, set []))
+
+(3,13)-(3,15) parse error Unexpected symbol '->' in value signature