Converting ForEach loop: avoid duplicate variable compilation issue

Fixes #558

Author: GrahamTheCoder

CHANGELOG.md

@@ -12,6 +12,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 
 * Improve multi-declaration field conversion for arrrays - [#559](https://github.com/icsharpcode/CodeConverter/issues/559)
 * Add parentheses around ternary statement - [#565](https://github.com/icsharpcode/CodeConverter/issues/565)
+* When converting ForEach loop, avoid duplicate variable compilation issue [#558](https://github.com/icsharpcode/CodeConverter/issues/558)
 
 ### C# -> VB
 

CodeConverter/CSharp/MethodBodyExecutableStatementVisitor.cs

@@ -539,17 +539,23 @@ public override async Task<SyntaxList<StatementSyntax>> VisitForEachBlock(VBSynt
 
             TypeSyntax type;
             SyntaxToken id;
+            List<StatementSyntax> statements = new List<StatementSyntax>();
             if (stmt.ControlVariable is VBSyntax.VariableDeclaratorSyntax vds) {
                 var declaration = (await CommonConversions.SplitVariableDeclarations(vds)).Variables.Single().Decl;
                 type = declaration.Type;
                 id = declaration.Variables.Single().Identifier;
+            } else if (_semanticModel.GetSymbolInfo(stmt.ControlVariable).Symbol is ISymbol varSymbol) {
+                var v = (IdentifierNameSyntax) await stmt.ControlVariable.AcceptAsync(_expressionVisitor);
+                id = CommonConversions.CsEscapedIdentifier(GetUniqueVariableNameInScope(node, "current" + varSymbol.Name.ToPascalCase()));
+                statements.Add(SyntaxFactory.ExpressionStatement(SyntaxFactory.AssignmentExpression(SyntaxKind.SimpleAssignmentExpression, v, SyntaxFactory.IdentifierName(id))));
+                type = CommonConversions.GetTypeSyntax(varSymbol.GetSymbolType());
             } else {
                 var v = (IdentifierNameSyntax) await stmt.ControlVariable.AcceptAsync(_expressionVisitor);
                 id = v.Identifier;
                 type = SyntaxFactory.ParseTypeName("var");
             }
 
-            var block = SyntaxFactory.Block(await ConvertStatements(node.Statements));
+            var block = SyntaxFactory.Block(statements.Concat(await ConvertStatements(node.Statements)));
             var csExpression = (ExpressionSyntax)await stmt.Expression.AcceptAsync(_expressionVisitor);
             return SingleStatement(SyntaxFactory.ForEachStatement(
                 type,

Tests/CSharp/StatementTests/LoopStatementTests.cs

@@ -138,21 +138,21 @@ public async Task ForEachStatementWithExplicitTypeAsync()
         {
             await TestConversionVisualBasicToCSharpAsync(@"Class TestClass
     Private Sub TestMethod(ByVal values As Integer())
-        For Each val As Integer In values
-            If val = 2 Then Continue For
-            If val = 3 Then Exit For
+        For Each v As Integer In values
+            If v = 2 Then Continue For
+            If v = 3 Then Exit For
         Next
     End Sub
 End Class", @"
 internal partial class TestClass
 {
     private void TestMethod(int[] values)
     {
-        foreach (int val in values)
+        foreach (int v in values)
         {
-            if (val == 2)
+            if (v == 2)
                 continue;
-            if (val == 3)
+            if (v == 3)
                 break;
         }
     }
@@ -164,6 +164,33 @@ public async Task ForEachStatementWithVarAsync()
         {
             await TestConversionVisualBasicToCSharpAsync(@"Class TestClass
     Private Sub TestMethod(ByVal values As Integer())
+        For Each v In values
+            If v = 2 Then Continue For
+            If v = 3 Then Exit For
+        Next
+    End Sub
+End Class", @"
+internal partial class TestClass
+{
+    private void TestMethod(int[] values)
+    {
+        foreach (var v in values)
+        {
+            if (v == 2)
+                continue;
+            if (v == 3)
+                break;
+        }
+    }
+}");
+        }
+
+        [Fact]
+        public async Task ForEachStatementWithOuterDeclarationAsync()
+        {
+            await TestConversionVisualBasicToCSharpAsync(@"Class TestClass
+    Private Sub TestMethod(ByVal values As Integer())
+        Dim val As Integer
         For Each val In values
             If val = 2 Then Continue For
             If val = 3 Then Exit For
@@ -174,17 +201,17 @@ internal partial class TestClass
 {
     private void TestMethod(int[] values)
     {
-        foreach (var val in values)
+        int val;
+        foreach (int currentVal in values)
         {
+            val = currentVal;
             if (val == 2)
                 continue;
             if (val == 3)
                 break;
         }
     }
-}
-1 source compilation errors:
-BC30516: Overload resolution failed because no accessible 'Val' accepts this number of arguments.");
+}");
         }
 
         [Fact]