DisallowShadowing: implemented rule

Implemented DisallowShadowing rule.

Author: webwarrior-ws

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

@@ -1,21 +1,136 @@
 module FSharpLint.Rules.DisallowShadowing
 
 open System
-
+open FSharp.Compiler.Syntax
 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 rec private extractIdentifiersFromSimplePats (simplePats: SynSimplePats) : List<Ident> =
+    let rec extractIdentifier (pattern: SynSimplePat) =
+        match pattern with
+        | SynSimplePat.Id(ident, _, _, _, _, _) ->
+            ident
+        | SynSimplePat.Attrib(pat, _, _)
+        | SynSimplePat.Typed(pat, _, _) ->
+            extractIdentifier pat
+
+    match simplePats with
+    | SynSimplePats.SimplePats(patterns, _) ->
+        patterns |> List.map extractIdentifier
+    | SynSimplePats.Typed(pats, _, _) -> 
+        extractIdentifiersFromSimplePats pats
+
+
+let private checkIdentifier (args: AstNodeRuleParams) (identifier: Ident) : array<WarningDetails> =
+    let name = identifier.idText
+    match args.CheckInfo with
+    | Some checkResults -> 
+        let allUsages = checkResults.GetAllUsesOfAllSymbolsInFile()
+        let definitionsWithSameName = 
+            allUsages 
+            |> Seq.filter (fun usage -> usage.IsFromDefinition && usage.Symbol.DisplayName = name)
+
+        let definitionsBeforeCurrent =
+            definitionsWithSameName
+            |> Seq.filter 
+                (fun usage -> 
+                    (usage.Range.StartLine, usage.Range.StartColumn) 
+                        < (identifier.idRange.StartLine, identifier.idRange.StartColumn) )
+            |> Seq.toArray
+
+        let rangeIncludedsDefinitions range =
+            definitionsBeforeCurrent
+            |> Array.exists (fun usage -> ExpressionUtilities.rangeContainsOtherRange range usage.Range)
+        
+        let processBinding binding =
+            match binding with
+            | SynBinding(_, _, _, _, _, _, _, _, _, _, range, _, _) ->
+                rangeIncludedsDefinitions range
+
+        let processArgs (args: SynSimplePats) =
+            args
+            |> extractIdentifiersFromSimplePats
+            |> List.exists (fun ident -> rangeIncludedsDefinitions ident.idRange)
+
+        let rec processExpression (expression: SynExpr) =
+            match expression with
+            | SynExpr.LetOrUse(_, _, bindings, _, _, _) ->
+                bindings |> List.exists processBinding
+            | SynExpr.Sequential(_, _, expr1, expr2, _) ->
+                processExpression expr1 || processExpression expr2
+            | SynExpr.Lambda(_, _, args, body, _, _, _) ->
+                processExpression body || processArgs args
+            | _ -> false
+
+        let rec processPattern (pattern: SynPat) =
+            match pattern with
+            | SynPat.Named(SynIdent(ident, _), _, _, _) -> rangeIncludedsDefinitions ident.idRange
+            | SynPat.Ands(pats, _) -> pats |> List.exists processPattern
+            | SynPat.Or(lhs, rhs, _, _) -> processPattern lhs || processPattern rhs
+            | SynPat.ArrayOrList(_, pats, _) -> pats |> List.exists processPattern
+            | SynPat.As(_lhs, rhs, _) -> processPattern rhs
+            | SynPat.OptionalVal(ident, _) -> rangeIncludedsDefinitions ident.idRange
+            | SynPat.Paren(pat, _) -> processPattern pat
+            | SynPat.Record(fieldPats, _) -> fieldPats |> List.exists (fun (_, _, pat) -> processPattern pat)
+            | SynPat.Tuple(_, pats, _) -> pats |> List.exists processPattern
+            | SynPat.Typed(pat, _, _) -> processPattern pat
+            | _ -> false
+
+        let processModuleDeclaration (moduleDecl: SynModuleDecl) =
+            match moduleDecl with
+            | SynModuleDecl.Let(_, bindings, _) ->
+                bindings 
+                |> List.exists processBinding
+            | _ -> false
+
+        let processAstNode (node: AstNode) =
+            match node with
+            | ModuleOrNamespace(SynModuleOrNamespace(_, _, _, declarations, _, _, _, _, _)) ->
+                declarations |> List.exists processModuleDeclaration
+            | Expression(expression) ->
+                processExpression (ExpressionUtilities.removeParens expression)
+            | Lambda(lambda, _) ->
+                processExpression lambda.Body
+                || (lambda.Arguments |> List.exists processArgs)
+            | Match(SynMatchClause(pattern, _, _, _, _, _)) ->
+                processPattern pattern
+            | MemberDefinition(SynMemberDefn.Member(memberDefn, _)) ->
+                processBinding memberDefn
+            | TypeDefinition(SynTypeDefn(_, _, _, Some(SynMemberDefn.ImplicitCtor(_, _, ctorArgs, _, _, _)), _, _)) ->
+                processArgs ctorArgs
+            | _ -> false
+
+        let parents = args.GetParents args.NodeIndex
+        let isShadowing =
+            parents |> List.exists processAstNode
+
+        if isShadowing then
+            Array.singleton { 
+                Range = identifier.idRange
+                Message = "RulesDisallowShadowing"
+                SuggestedFix = None
+                TypeChecks = List.Empty }
+        else
+            Array.empty
+                
+    | None -> Array.empty
+
 let runner (args: AstNodeRuleParams) =
-    
-    failwith "Not yet implemented"
+    match args.AstNode with
+    | Pattern(SynPat.Named(SynIdent(ident, _), _, _, _)) ->
+        checkIdentifier args ident
+    | Lambda(lambda, _) ->
+        lambda.Arguments 
+        |> List.collect extractIdentifiersFromSimplePats
+        |> List.toArray
+        |> Array.collect (fun each -> checkIdentifier args each)
+    | _ ->
+        Array.empty
 
 let rule =
     { Name = "DisallowShadowing"
       Identifier = Identifiers.DisallowShadowing
       RuleConfig = { AstNodeRuleConfig.Runner = runner; Cleanup = ignore } }
-    |> AstNodeRule
+    |> AstNodeRule