public ForeachStatement TransformNonGenericForEach(ExpressionStatement node)
{
Match m1 = getEnumeratorPattern.Match(node);
if (!m1.Success)
{
return(null);
}
AstNode tryCatch = node.NextSibling;
Match m2 = nonGenericForeachPattern.Match(tryCatch);
if (!m2.Success)
{
return(null);
}
IdentifierExpression enumeratorVar = m2.Get <IdentifierExpression>("enumerator").Single();
IdentifierExpression itemVar = m2.Get <IdentifierExpression>("itemVar").Single();
WhileStatement loop = m2.Get <WhileStatement>("loop").Single();
// verify that the getEnumeratorPattern assigns to the same variable as the nonGenericForeachPattern is reading from
if (!enumeratorVar.IsMatch(m1.Get("left").Single()))
{
return(null);
}
VariableDeclarationStatement enumeratorVarDecl = FindVariableDeclaration(loop, enumeratorVar.Identifier);
if (enumeratorVarDecl == null || !(enumeratorVarDecl.Parent is BlockStatement))
{
return(null);
}
// Find the declaration of the item variable:
// Because we look only outside the loop, we won't make the mistake of moving a captured variable across the loop boundary
VariableDeclarationStatement itemVarDecl = FindVariableDeclaration(loop, itemVar.Identifier);
if (itemVarDecl == null || !(itemVarDecl.Parent is BlockStatement))
{
return(null);
}
// Now verify that we can move the variable declaration in front of the loop:
Statement declarationPoint;
CanMoveVariableDeclarationIntoStatement(itemVarDecl, loop, out declarationPoint);
// We ignore the return value because we don't care whether we can move the variable into the loop
// (that is possible only with non-captured variables).
// We just care that we can move it in front of the loop:
if (declarationPoint != loop)
{
return(null);
}
ForeachStatement foreachStatement = new ForeachStatement();
foreachStatement.VariableType = itemVarDecl.Type.Clone();
foreachStatement.VariableName = itemVar.Identifier;
BlockStatement body = new BlockStatement();
foreachStatement.EmbeddedStatement = body;
((BlockStatement)node.Parent).Statements.InsertBefore(node, foreachStatement);
body.Add(node.Detach());
body.Add((Statement)tryCatch.Detach());
// Now that we moved the whole try-catch into the foreach loop; verify that we can
// move the enumerator into the foreach loop:
CanMoveVariableDeclarationIntoStatement(enumeratorVarDecl, foreachStatement, out declarationPoint);
if (declarationPoint != foreachStatement)
{
// oops, the enumerator variable can't be moved into the foreach loop
// Undo our AST changes:
((BlockStatement)foreachStatement.Parent).Statements.InsertBefore(foreachStatement, node.Detach());
foreachStatement.ReplaceWith(tryCatch);
return(null);
}
// Now create the correct body for the foreach statement:
foreachStatement.InExpression = m1.Get <Expression>("collection").Single().Detach();
if (foreachStatement.InExpression is BaseReferenceExpression)
{
foreachStatement.InExpression = new ThisReferenceExpression().CopyAnnotationsFrom(foreachStatement.InExpression);
}
body.Statements.Clear();
body.Statements.AddRange(m2.Get <Statement>("stmt").Select(stmt => stmt.Detach()));
return(foreachStatement);
}