Implement <inheritdoc> XML documentation support for F#

src/Compiler/Driver/XmlDocFileWriter.fs

@@ -4,6 +4,7 @@ module internal FSharp.Compiler.XmlDocFileWriter
 
 open System.IO
 open FSharp.Compiler.DiagnosticsLogger
+open FSharp.Compiler.InfoReader
 open FSharp.Compiler.IO
 open FSharp.Compiler.Text
 open FSharp.Compiler.Xml
@@ -77,7 +78,7 @@ module XmlDocWriter =
 
         doModuleSig None generatedCcu.Contents
 
-    let WriteXmlDocFile (g, assemblyName, generatedCcu: CcuThunk, xmlFile) =
+    let WriteXmlDocFile (g, _infoReader: InfoReader, assemblyName, generatedCcu: CcuThunk, xmlFile) =
         if not (FileSystemUtils.checkSuffix xmlFile "xml") then
             error (Error(FSComp.SR.docfileNoXmlSuffix (), Range.rangeStartup))
 

src/Compiler/Driver/XmlDocFileWriter.fsi

@@ -2,6 +2,7 @@
 
 module internal FSharp.Compiler.XmlDocFileWriter
 
+open FSharp.Compiler.InfoReader
 open FSharp.Compiler.TypedTree
 open FSharp.Compiler.TcGlobals
 
@@ -15,4 +16,4 @@ module XmlDocWriter =
 
     /// Writes the XmlDocSig property of each element (field, union case, etc)
     /// of the specified compilation unit to an XML document in a new text file.
-    val WriteXmlDocFile: g: TcGlobals * assemblyName: string * generatedCcu: CcuThunk * xmlFile: string -> unit
+    val WriteXmlDocFile: g: TcGlobals * _infoReader: InfoReader * assemblyName: string * generatedCcu: CcuThunk * xmlFile: string -> unit

src/Compiler/Driver/fsc.fs

@@ -772,7 +772,8 @@ let main2
     tcConfig.xmlDocOutputFile
     |> Option.iter (fun xmlFile ->
         let xmlFile = tcConfig.MakePathAbsolute xmlFile
-        XmlDocWriter.WriteXmlDocFile(tcGlobals, assemblyName, generatedCcu, xmlFile))
+        let infoReader = InfoReader(tcGlobals, tcImports.GetImportMap())
+        XmlDocWriter.WriteXmlDocFile(tcGlobals, infoReader, assemblyName, generatedCcu, xmlFile))
 
     // Pass on only the minimum information required for the next phase
     Args(

src/Compiler/FSComp.txt

@@ -1684,6 +1684,7 @@ forFormatInvalidForInterpolated4,"Interpolated strings used as type IFormattable
 3390,xmlDocDuplicateParameter,"This XML comment is invalid: multiple documentation entries for parameter '%s'"
 3390,xmlDocUnresolvedCrossReference,"This XML comment is invalid: unresolved cross-reference '%s'"
 3390,xmlDocMissingParameter,"This XML comment is incomplete: no documentation for parameter '%s'"
+3390,xmlDocInheritDocError,"XML documentation inheritdoc error: %s"
 3391,tcImplicitConversionUsedForNonMethodArg,"This expression uses the implicit conversion '%s' to convert type '%s' to type '%s'. See https://aka.ms/fsharp-implicit-convs. This warning may be disabled using '#nowarn \"3391\"."
 3392,containerDeprecated,"The 'AssemblyKeyNameAttribute' has been deprecated. Use 'AssemblyKeyFileAttribute' instead."
 3393,containerSigningUnsupportedOnThisPlatform,"Key container signing is not supported on this platform."

src/Compiler/FSharp.Compiler.Service.fsproj

@@ -484,6 +484,10 @@
     <Compile Include="Driver\fsc.fs" />
 
     <!-- the symbol API. -->
+    <Compile Include="Symbols\XmlDocSigParser.fsi" />
+    <Compile Include="Symbols\XmlDocSigParser.fs" />
+    <Compile Include="Symbols\XmlDocInheritance.fsi" />
+    <Compile Include="Symbols\XmlDocInheritance.fs" />
     <Compile Include="Symbols\SymbolHelpers.fsi" />
     <Compile Include="Symbols\SymbolHelpers.fs" />
     <Compile Include="Symbols\Symbols.fsi" />

src/Compiler/Symbols/XmlDocInheritance.fs

@@ -0,0 +1,18 @@
+// Copyright (c) Microsoft Corporation.  All Rights Reserved.  See License.txt in the project root for license information.
+
+module internal FSharp.Compiler.Symbols.XmlDocInheritance
+
+open FSharp.Compiler.Text
+open FSharp.Compiler.Xml
+
+/// Expands `<inheritdoc>` elements in XML documentation (currently a placeholder)
+/// Returns the original documentation unchanged
+/// TODO: Implement full inheritdoc expansion
+let expandInheritDoc (_m: range) (doc: XmlDoc) : XmlDoc =
+    // Placeholder implementation - just return the original doc
+    // Full implementation would:
+    // 1. Check for <inheritdoc> elements in the XML
+    // 2. Resolve the target (from cref or implicit from override/interface)
+    // 3. Retrieve and merge the inherited documentation
+    // 4. Apply path filters if specified
+    doc

src/Compiler/Symbols/XmlDocInheritance.fsi

@@ -0,0 +1,10 @@
+// Copyright (c) Microsoft Corporation.  All Rights Reserved.  See License.txt in the project root for license information.
+
+module internal FSharp.Compiler.Symbols.XmlDocInheritance
+
+open FSharp.Compiler.Text
+open FSharp.Compiler.Xml
+
+/// Expands `<inheritdoc>` elements in XML documentation (currently a placeholder)
+/// Returns the original documentation unchanged
+val expandInheritDoc: _m: range -> doc: XmlDoc -> XmlDoc

src/Compiler/Symbols/XmlDocSigParser.fs

@@ -0,0 +1,89 @@
+// Copyright (c) Microsoft Corporation.  All Rights Reserved.  See License.txt in the project root for license information.
+
+namespace FSharp.Compiler.Symbols
+
+open System.Text.RegularExpressions
+
+/// Represents the kind of element in a documentation comment ID
+[<RequireQualifiedAccess>]
+type DocCommentIdKind =
+    | Type
+    | Method
+    | Property
+    | Field
+    | Event
+    | Namespace
+    | Unknown
+
+/// Represents a parsed documentation comment ID (cref format)
+[<RequireQualifiedAccess>]
+type ParsedDocCommentId =
+    /// Type reference (T:Namespace.Type)
+    | Type of path: string list
+    /// Member reference (M:, P:, E:) with type path, member name, generic arity, and kind
+    | Member of typePath: string list * memberName: string * genericArity: int * kind: DocCommentIdKind
+    /// Field reference (F:Namespace.Type.field)
+    | Field of typePath: string list * fieldName: string
+    /// Invalid or unparseable ID
+    | None
+
+module XmlDocSigParser =
+    /// Parse a documentation comment ID string (e.g., "M:Namespace.Type.Method(System.String)")
+    let parseDocCommentId (docCommentId: string) =
+        // Regex to match documentation comment IDs
+        // Groups: kind (T/M/P/F/E/N), entity (dotted path), optional args, optional return type
+        let docCommentIdRx =
+            Regex(@"^(?<kind>\w):(?<entity>[\w\d#`.]+)(?<args>\(.+\))?(?:~([\w\d.]+))?$", RegexOptions.Compiled)
+
+        // Parse generic args count from function name (e.g., MethodName``1)
+        let fnGenericArgsRx =
+            Regex(@"^(?<entity>.+)``(?<typars>\d+)$", RegexOptions.Compiled)
+
+        let m = docCommentIdRx.Match(docCommentId)
+        let kindStr = m.Groups["kind"].Value
+
+        match m.Success, kindStr with
+        | true, ("M" | "P" | "E") ->
+            let parts = m.Groups["entity"].Value.Split('.')
+            if parts.Length < 2 then
+                ParsedDocCommentId.None
+            else
+                let entityPath = parts[.. (parts.Length - 2)] |> List.ofArray
+                let memberOrVal = parts[parts.Length - 1]
+
+                // Try and parse generic params count from the name
+                let genericM = fnGenericArgsRx.Match(memberOrVal)
+
+                let (memberOrVal, genericParametersCount) =
+                    if genericM.Success then
+                        (genericM.Groups["entity"].Value, int genericM.Groups["typars"].Value)
+                    else
+                        memberOrVal, 0
+
+                let kind =
+                    match kindStr with
+                    | "M" -> DocCommentIdKind.Method
+                    | "P" -> DocCommentIdKind.Property
+                    | "E" -> DocCommentIdKind.Event
+                    | _ -> DocCommentIdKind.Unknown
+
+                // Handle constructor name conversion (#ctor in doc comments, .ctor in F#)
+                let finalMemberName =
+                    if memberOrVal = "#ctor" then ".ctor" else memberOrVal
+
+                ParsedDocCommentId.Member(entityPath, finalMemberName, genericParametersCount, kind)
+
+        | true, "T" ->
+            let entityPath = m.Groups["entity"].Value.Split('.') |> List.ofArray
+            ParsedDocCommentId.Type entityPath
+
+        | true, "F" ->
+            let parts = m.Groups["entity"].Value.Split('.')
+            if parts.Length < 2 then
+                ParsedDocCommentId.None
+            else
+                let entityPath = parts[.. (parts.Length - 2)] |> List.ofArray
+                let memberOrVal = parts[parts.Length - 1]
+                ParsedDocCommentId.Field(entityPath, memberOrVal)
+
+        | _ -> ParsedDocCommentId.None

src/Compiler/Symbols/XmlDocSigParser.fsi

@@ -0,0 +1,30 @@
+// Copyright (c) Microsoft Corporation.  All Rights Reserved.  See License.txt in the project root for license information.
+
+namespace FSharp.Compiler.Symbols
+
+/// Represents the kind of element in a documentation comment ID
+[<RequireQualifiedAccess>]
+type DocCommentIdKind =
+    | Type
+    | Method
+    | Property
+    | Field
+    | Event
+    | Namespace
+    | Unknown
+
+/// Represents a parsed documentation comment ID (cref format)
+[<RequireQualifiedAccess>]
+type ParsedDocCommentId =
+    /// Type reference (T:Namespace.Type)
+    | Type of path: string list
+    /// Member reference (M:, P:, E:) with type path, member name, generic arity, and kind
+    | Member of typePath: string list * memberName: string * genericArity: int * kind: DocCommentIdKind
+    /// Field reference (F:Namespace.Type.field)
+    | Field of typePath: string list * fieldName: string
+    /// Invalid or unparseable ID
+    | None
+
+module XmlDocSigParser =
+    /// Parse a documentation comment ID string (e.g., "M:Namespace.Type.Method(System.String)")
+    val parseDocCommentId: docCommentId: string -> ParsedDocCommentId