UsedUnderscorePrefixedElements: fix rule

Fix rule so that it identifies all usages of identifiers that
start with `_`.

src/FSharpLint.Core/Rules/Conventions/UsedUnderscorePrefixedElements.fs

@@ -5,51 +5,45 @@ open System
 open FSharpLint.Framework
 open FSharpLint.Framework.Suggestion
 open FSharp.Compiler.Syntax
+open FSharp.Compiler.Text
+open FSharp.Compiler.CodeAnalysis
 open FSharpLint.Framework.Ast
 open FSharpLint.Framework.Rules
 
-let private checkUsedIdent (previousIdent: Ident) (body: SynExpr) =
-    match body with
-    | SynExpr.Sequential(_debugPointAtSequential, _isTrueSeq, synExpr, _expr2, _range) ->
-        match synExpr with
-        | SynExpr.App(_exprAtomicFlag, _isInfix, _funcExpr, argExpr, range) ->
-            match argExpr with
-            | SynExpr.Ident ident ->
-                if previousIdent.idText = ident.idText then
-                    {
-                        Range = range
+let private checkUsedIdent (identifier: Ident) (usages: array<FSharpSymbolUse>) (scopeRange: Range) =
+    usages
+    |> Array.collect (fun usage ->
+        if not usage.IsFromDefinition && usage.Symbol.FullName = identifier.idText 
+            && ExpressionUtilities.rangeContainsOtherRange scopeRange usage.Range then
+            {
+                Range = usage.Range
+                Message = String.Format(Resources.GetString ("RulesUsedUnderscorePrefixedElements"))
+                SuggestedFix = None
+                TypeChecks = List.Empty
+            } |> Array.singleton
+        else
+            Array.empty)
+
+let runner (args: AstNodeRuleParams) =
+    // hack to only run rule once
+    if args.NodeIndex = 0 then
+        match args.CheckInfo with
+        | Some checkResults -> 
+            checkResults.GetAllUsesOfAllSymbolsInFile() 
+            |> Seq.choose (fun usage ->
+                if not usage.IsFromDefinition && usage.Symbol.FullName.StartsWith "_" then
+                    Some {
+                        Range = usage.Range
                         Message = String.Format(Resources.GetString ("RulesUsedUnderscorePrefixedElements"))
                         SuggestedFix = None
                         TypeChecks = List.Empty
-                    } |> Array.singleton
+                    }
                 else
-                    Array.empty
-            | _ ->
-                Array.empty
-        | _ ->
-            Array.empty
-    | _ ->
-        Array.empty  
-
-let runner (args: AstNodeRuleParams) =
-
-    let error =
-        match args.AstNode with
-        | AstNode.Expression (SynExpr.LetOrUse (_isRecursive, _isUse, bindings, body, _range)) ->
-            match List.tryHead bindings with
-            | Some(SynBinding(_synAccessOption, _synBindingKind, _mustInline, _isMutable, _synAttributeLists, _preXmlDoc, _synValData, headPat, _synBindingReturnInfoOption, _synExpr, _range, _debugPointAtBinding)) ->
-                match headPat with
-                | SynPat.Named(_synPat, ident, _isSelfIdentifier, _synAccessOption, _range) ->
-                    if ident.idText.StartsWith "_" then
-                        checkUsedIdent ident body
-                    else
-                        Array.empty
-                | _ ->
-                    Array.empty
-            | _ -> Array.empty
-        | _ -> Array.empty
-
-    error
+                    None)
+            |> Seq.toArray
+        | None -> Array.empty
+    else
+        Array.empty
 
 let rule =
     { Name = "UsedUnderscorePrefixedElements"