Elm-like compiler errors for name resolution

src/fsharp/CompileOps.fs

@@ -742,8 +742,12 @@ let OutputPhasedErrorR (os:System.Text.StringBuilder) (err:PhasedError) =
               os.Append(Duplicate1E().Format (DecompileOpName s)) |> ignore
           else 
               os.Append(Duplicate2E().Format k (DecompileOpName s)) |> ignore
-      | UndefinedName(_,k,id,_) -> 
+      | UndefinedName(_,k,id,predictions) ->
           os.Append(k (DecompileOpName id.idText)) |> ignore
+          if Set.isEmpty predictions |> not then
+              let filtered = ErrorResolutionHints.FilterPredictions id.idText predictions
+              os.Append(ErrorResolutionHints.FormatPredictions filtered) |> ignore
+
       | InternalUndefinedItemRef(f,smr,ccuName,s) ->  
           let _, errs = f(smr, ccuName, s)  
           os.Append(errs) |> ignore  

src/fsharp/ErrorResolutionHints.fs

@@ -0,0 +1,29 @@
+// Copyright (c) Microsoft Corporation.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
+
+/// Functions to format error message details
+module internal Microsoft.FSharp.Compiler.ErrorResolutionHints
+
+/// Filters predictions based on edit distance to an unknown identifier.
+let FilterPredictions unknownIdent allPredictions =
+    let rec take n predictions = 
+        predictions 
+        |> Seq.mapi (fun i x -> i,x) 
+        |> Seq.takeWhile (fun (i,_) -> i < n) 
+        |> Seq.map snd 
+        |> Seq.toList
+
+    allPredictions
+    |> Seq.toList
+    |> List.distinct
+    |> List.sortBy (fun s -> Internal.Utilities.EditDistance.CalcEditDistance(unknownIdent,s))
+    |> take 5
+
+let FormatPredictions predictions =
+    match predictions with
+    | [] -> System.String.Empty
+    | _ ->
+        let predictionText =
+            predictions 
+            |> Seq.map (sprintf "%s   %s" System.Environment.NewLine) 
+            |> String.concat ""
+        System.Environment.NewLine  + FSComp.SR.undefinedNameRecordLabelDetails() + predictionText

src/fsharp/FSComp.txt

@@ -9,8 +9,10 @@ undefinedNameValueOfConstructor,"The value or constructor '%s' is not defined"
 undefinedNameValueNamespaceTypeOrModule,"The value, namespace, type or module '%s' is not defined"
 undefinedNameConstructorModuleOrNamespace,"The constructor, module or namespace '%s' is not defined"
 undefinedNameType,"The type '%s' is not defined"
+undefinedNameTypeIn,"The type '%s' is not defined in '%s'."
 undefinedNameRecordLabelOrNamespace,"The record label or namespace '%s' is not defined"
-undefinedNameRecordLabel,"The record label '%s' is not defined"
+undefinedNameRecordLabel,"The record label '%s' is not defined."
+undefinedNameRecordLabelDetails,"Maybe you want one of the following:"
 undefinedNameTypeParameter,"The type parameter '%s' is not defined"
 undefinedNamePatternDiscriminator,"The pattern discriminator '%s' is not defined"
 missingElseBranch,"The 'if' expression is missing an 'else' branch. The 'then' branch has type '%s'. Because 'if' is an expression, and not a statement, add an 'else' branch which returns a value of the same type."
@@ -951,6 +953,7 @@ lexfltSeparatorTokensOfPatternMatchMisaligned,"The '|' tokens separating rules o
 1127,nrIsNotConstructorOrLiteral,"This is not a constructor or literal, or a constructor is being used incorrectly"
 1128,nrUnexpectedEmptyLongId,"Unexpected empty long identifier"
 1129,nrTypeDoesNotContainSuchField,"The type '%s' does not contain a field '%s'"
+1129,nrRecordDoesNotContainSuchLabel,"The record type '%s' does not contain a label '%s'."
 1130,nrInvalidFieldLabel,"Invalid field label"
 1132,nrInvalidExpression,"Invalid expression '%s'"
 1133,nrNoConstructorsAvailableForType,"No constructors are available for the type '%s'"

src/fsharp/FSharp.Compiler-proto/FSharp.Compiler-proto.fsproj

@@ -98,6 +98,9 @@
     <Compile Include="..\..\utils\HashMultiMap.fs">
       <Link>HashMultiMap.fs</Link>
     </Compile>
+    <Compile Include="..\..\utils\EditDistance.fs">
+      <Link>Utilities\EditDistance.fs</Link>
+    </Compile>
     <Compile Include="..\..\utils\TaggedCollections.fsi">
       <Link>TaggedCollections.fsi</Link>
     </Compile>
@@ -211,6 +214,9 @@
     <Compile Include="..\ErrorLogger.fs">
       <Link>ErrorLogger.fs</Link>
     </Compile>
+    <Compile Include="..\ErrorResolutionHints.fs">
+      <Link>ErrorResolutionHints.fs</Link>
+    </Compile>
     <Compile Include="..\InternalCollections.fsi">
       <Link>InternalCollections.fsi</Link>
     </Compile>

src/fsharp/FSharp.Compiler/FSharp.Compiler.fsproj

@@ -1,4 +1,4 @@
-<?xml version="1.0" encoding="utf-8"?>
+<?xml version="1.0" encoding="utf-8"?>
 <!-- Copyright (c) Microsoft Corporation.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information. -->
 <Project ToolsVersion="4.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <PropertyGroup>
@@ -84,6 +84,9 @@
     <Compile Include="..\..\utils\HashMultiMap.fs">
       <Link>Utilities\HashMultiMap.fs</Link>
     </Compile>
+    <Compile Include="..\..\utils\EditDistance.fs">
+      <Link>Utilities\EditDistance.fs</Link>
+    </Compile>
     <Compile Include="..\..\utils\TaggedCollections.fsi">
       <Link>Utilities\TaggedCollections.fsi</Link>
     </Compile>
@@ -159,6 +162,9 @@
     <Compile Include="..\ErrorLogger.fs">
       <Link>ErrorLogging\ErrorLogger.fs</Link>
     </Compile>
+    <Compile Include="..\ErrorResolutionHints.fs">
+      <Link>ErrorLogging\ErrorResolutionHints.fs</Link>
+    </Compile>
     <Compile Include="..\ReferenceResolution.fsi">
       <Link>ReferenceResolution\ReferenceResolution.fsi</Link>
     </Compile>

src/fsharp/FSharp.LanguageService.Compiler/FSharp.LanguageService.Compiler.fsproj

@@ -80,6 +80,9 @@
     <Compile Include="..\..\utils\HashMultiMap.fs">
       <Link>Utilities\HashMultiMap.fs</Link>
     </Compile>
+    <Compile Include="..\..\utils\EditDistance.fs">
+      <Link>Utilities\EditDistance.fs</Link>
+    </Compile>
     <Compile Include="..\..\utils\TaggedCollections.fsi">
       <Link>Utilities\TaggedCollections.fsi</Link>
     </Compile>
@@ -152,6 +155,9 @@
     <Compile Include="..\ErrorLogger.fs">
       <Link>ErrorLogging\ErrorLogger.fs</Link>
     </Compile>
+    <Compile Include="..\ErrorResolutionHints.fs">
+      <Link>ErrorLogging\ErrorResolutionHints.fs</Link>
+    </Compile>
     <Compile Include="..\ReferenceResolution.fsi">
       <Link>ReferenceResolution\ReferenceResolution.fsi</Link>
     </Compile>