private Expression VisitYield(YieldExpression node)
{
if (node.Target != _generator.Target)
{
throw new InvalidOperationException("yield and generator must have the same LabelTarget object");
}
var value = Visit(node.Value);
var block = new ReadOnlyCollectionBuilder <Expression>();
if (value == null)
{
// Yield break
block.Add(Expression.Assign(_state, AstUtils.Constant(Finished)));
if (_inTryWithFinally)
{
block.Add(Expression.Assign(_gotoRouter, AstUtils.Constant(GotoRouterYielding)));
}
block.Add(Expression.Goto(_returnLabels.Peek()));
return(Expression.Block(block));
}
// Yield return
block.Add(MakeAssign(_current, value));
YieldMarker marker = GetYieldMarker(node);
block.Add(Expression.Assign(_state, AstUtils.Constant(marker.State)));
if (_inTryWithFinally)
{
block.Add(Expression.Assign(_gotoRouter, AstUtils.Constant(GotoRouterYielding)));
}
block.Add(Expression.Goto(_returnLabels.Peek()));
block.Add(Expression.Label(marker.Label));
block.Add(Expression.Assign(_gotoRouter, AstUtils.Constant(GotoRouterNone)));
block.Add(Utils.Empty());
return(Expression.Block(block));
}
/// <summary>
/// Transform multiple python except handlers for a try block into a single catch body.
/// </summary>
/// <param name="exception">The variable for the exception in the catch block.</param>
/// <returns>Null if there are no except handlers. Else the statement to go inside the catch handler</returns>
private MSAst.Expression TransformHandlers(MSAst.ParameterExpression exception)
{
Assert.NotEmpty(_handlers);
MSAst.ParameterExpression extracted = Ast.Variable(typeof(object), "$extracted");
var tests = new List <Microsoft.Scripting.Ast.IfStatementTest>(_handlers.Length);
MSAst.ParameterExpression converted = null;
MSAst.Expression catchAll = null;
for (int index = 0; index < _handlers.Length; index++)
{
TryStatementHandler tsh = _handlers[index];
if (tsh.Test != null)
{
Microsoft.Scripting.Ast.IfStatementTest ist;
// translating:
// except Test ...
//
// generate following AST for the Test (common part):
// CheckException(exception, Test)
MSAst.Expression test =
Ast.Call(
AstMethods.CheckException,
Parent.LocalContext,
extracted,
AstUtils.Convert(tsh.Test, typeof(object))
);
if (tsh.Target != null)
{
// translating:
// except Test, Target:
// <body>
// into:
// if ((converted = CheckException(exception, Test)) != null) {
// Target = converted;
// traceback-header
// <body>
// }
if (converted == null)
{
converted = Ast.Variable(typeof(object), "$converted");
}
ist = AstUtils.IfCondition(
Ast.NotEqual(
Ast.Assign(converted, test),
AstUtils.Constant(null)
),
Ast.Block(
tsh.Target.TransformSet(SourceSpan.None, converted, PythonOperationKind.None),
GlobalParent.AddDebugInfo(
GetTracebackHeader(
this,
exception,
tsh.Body
),
new SourceSpan(tsh.Start, tsh.Header)
),
AstUtils.Empty()
)
);
}
else
{
// translating:
// except Test:
// <body>
// into:
// if (CheckException(exception, Test) != null) {
// traceback-header
// <body>
// }
ist = AstUtils.IfCondition(
Ast.NotEqual(
test,
AstUtils.Constant(null)
),
GlobalParent.AddDebugInfo(
GetTracebackHeader(
this,
exception,
tsh.Body
),
new SourceSpan(tsh.Start, tsh.Header)
)
);
}
// Add the test to the if statement test cascade
tests.Add(ist);
}
else
{
Debug.Assert(index == _handlers.Length - 1);
Debug.Assert(catchAll == null);
// translating:
// except:
// <body>
// into:
// {
// traceback-header
// <body>
// }
catchAll = GlobalParent.AddDebugInfo(
GetTracebackHeader(this, exception, tsh.Body),
new SourceSpan(tsh.Start, tsh.Header)
);
}
}
MSAst.Expression body = null;
if (tests.Count > 0)
{
// rethrow the exception if we have no catch-all block
if (catchAll == null)
{
catchAll = Ast.Block(
Parent.GetSaveLineNumberExpression(exception, true),
Ast.Throw(
Ast.Call(
typeof(ExceptionHelpers).GetMethod("UpdateForRethrow"),
exception
)
)
);
}
body = AstUtils.If(
tests.ToArray(),
catchAll
);
}
else
{
Debug.Assert(catchAll != null);
body = catchAll;
}
IList <MSAst.ParameterExpression> args;
if (converted != null)
{
args = new ReadOnlyCollectionBuilder <MSAst.ParameterExpression> {
converted, extracted
};
}
else
{
args = new ReadOnlyCollectionBuilder <MSAst.ParameterExpression> {
extracted
};
}
// Codegen becomes:
// extracted = PythonOps.SetCurrentException(exception)
// < dynamic exception analysis >
return(Ast.Block(
args,
Ast.Assign(
extracted,
Ast.Call(
AstMethods.SetCurrentException,
Parent.LocalContext,
exception
)
),
body,
Ast.Assign(extracted, Ast.Constant(null)),
AstUtils.Empty()
));
}
/// <summary>
/// Creates the LambdaExpression which implements the body of the function.
///
/// The functions signature is either "object Function(PythonFunction, ...)"
/// where there is one object parameter for each user defined parameter or
/// object Function(PythonFunction, object[]) for functions which take more
/// than PythonCallTargets.MaxArgs arguments.
/// </summary>
private LightLambdaExpression CreateFunctionLambda()
{
bool needsWrapperMethod = _parameters.Length > PythonCallTargets.MaxArgs;
Delegate originalDelegate;
Type delegateType = GetDelegateType(_parameters, needsWrapperMethod, out originalDelegate);
MSAst.ParameterExpression localContext = null;
ReadOnlyCollectionBuilder <MSAst.ParameterExpression> locals = new ReadOnlyCollectionBuilder <MSAst.ParameterExpression>();
if (NeedsLocalContext)
{
localContext = LocalCodeContextVariable;
locals.Add(localContext);
}
MSAst.ParameterExpression[] parameters = CreateParameters(needsWrapperMethod, locals);
List <MSAst.Expression> init = new List <MSAst.Expression>();
foreach (var param in _parameters)
{
IPythonVariableExpression pyVar = GetVariableExpression(param.PythonVariable) as IPythonVariableExpression;
if (pyVar != null)
{
var varInit = pyVar.Create();
if (varInit != null)
{
init.Add(varInit);
}
}
}
// Transform the parameters.
init.Add(Ast.ClearDebugInfo(GlobalParent.Document));
locals.Add(PythonAst._globalContext);
init.Add(Ast.Assign(PythonAst._globalContext, new GetGlobalContextExpression(_parentContext)));
GlobalParent.PrepareScope(locals, init);
// Create variables and references. Since references refer to
// parameters, do this after parameters have been created.
CreateFunctionVariables(locals, init);
// If the __class__ variable is used the a class method then we need to initialize it.
// This must be done before parameter initialization (in case one of the parameters is called __class__).
ClassDefinition parent = FindParentOfType <ClassDefinition>();
PythonVariable pVar;
if (parent != null && TryGetVariable("__class__", out pVar))
{
init.Add(
AssignValue(
GetVariableExpression(pVar),
Ast.Call(AstMethods.LookupName, parent.Parent.LocalContext, Ast.Constant(parent.Name))
)
);
}
// Initialize parameters - unpack tuples.
// Since tuples unpack into locals, this must be done after locals have been created.
InitializeParameters(init, needsWrapperMethod, parameters);
List <MSAst.Expression> statements = new List <MSAst.Expression>();
// add beginning sequence point
var start = GlobalParent.IndexToLocation(StartIndex);
statements.Add(GlobalParent.AddDebugInfo(
AstUtils.Empty(),
new SourceSpan(new SourceLocation(0, start.Line, start.Column), new SourceLocation(0, start.Line, Int32.MaxValue))));
// For generators, we need to do a check before the first statement for Generator.Throw() / Generator.Close().
// The exception traceback needs to come from the generator's method body, and so we must do the check and throw
// from inside the generator.
if (IsGenerator)
{
MSAst.Expression s1 = YieldExpression.CreateCheckThrowExpression(SourceSpan.None);
statements.Add(s1);
}
MSAst.ParameterExpression extracted = null;
if (!IsGenerator && _canSetSysExcInfo)
{
// need to allocate the exception here so we don't share w/ exceptions made & freed
// during the body.
extracted = Ast.Parameter(typeof(Exception), "$ex");
locals.Add(extracted);
}
if (_body.CanThrow && !(_body is SuiteStatement) && _body.StartIndex != -1)
{
statements.Add(UpdateLineNumber(GlobalParent.IndexToLocation(_body.StartIndex).Line));
}
statements.Add(Body);
MSAst.Expression body = Ast.Block(statements);
// If this function can modify sys.exc_info() (_canSetSysExcInfo), then it must restore the result on finish.
//
// Wrap in
// $temp = PythonOps.SaveCurrentException()
// <body>
// PythonOps.RestoreCurrentException($temp)
// Skip this if we're a generator. For generators, the try finally is handled by the PythonGenerator class
// before it's invoked. This is because the restoration must occur at every place the function returns from
// a yield point. That's different than the finally semantics in a generator.
if (extracted != null)
{
MSAst.Expression s = AstUtils.Try(
Ast.Assign(
extracted,
Ast.Call(AstMethods.SaveCurrentException)
),
body
).Finally(
Ast.Call(
AstMethods.RestoreCurrentException, extracted
)
);
body = s;
}
if (_body.CanThrow && GlobalParent.PyContext.PythonOptions.Frames)
{
body = AddFrame(LocalContext, Ast.Property(_functionParam, typeof(PythonFunction).GetProperty("__code__")), body);
locals.Add(FunctionStackVariable);
}
body = AddProfiling(body);
body = WrapScopeStatements(body, _body.CanThrow);
body = Ast.Block(body, AstUtils.Empty());
body = AddReturnTarget(body);
MSAst.Expression bodyStmt = body;
if (localContext != null)
{
var createLocal = CreateLocalContext(_parentContext);
init.Add(
Ast.Assign(
localContext,
createLocal
)
);
}
init.Add(bodyStmt);
bodyStmt = Ast.Block(init);
// wrap a scope if needed
bodyStmt = Ast.Block(locals.ToReadOnlyCollection(), bodyStmt);
return(AstUtils.LightLambda(
typeof(object),
delegateType,
AddDefaultReturn(bodyStmt, typeof(object)),
Name + "$" + Interlocked.Increment(ref _lambdaId),
parameters
));
}
private MSAst.Expression AddFinally(MSAst.Expression /*!*/ body)
{
if (Finally != null)
{
MSAst.ParameterExpression tryThrows = Ast.Variable(typeof(Exception), "$tryThrows");
MSAst.ParameterExpression locException = Ast.Variable(typeof(Exception), "$localException");
MSAst.Expression? @finally = Finally;
// lots is going on here. We need to consider:
// 1. Exceptions propagating out of try/except/finally. Here we need to save the line #
// from the exception block and not save the # from the finally block later.
// 2. Exceptions propagating out of the finally block. Here we need to report the line number
// from the finally block and leave the existing stack traces cleared.
// 3. Returning from the try block: Here we need to run the finally block and not update the
// line numbers.
body = AstUtils.Try(
// we use a fault to know when we have an exception and when control leaves normally (via
// either a return or the body completing successfully).
AstUtils.Try(
Parent.AddDebugInfo(AstUtils.Empty(), new SourceSpan(Span.Start, GlobalParent.IndexToLocation(HeaderIndex))),
Ast.Assign(tryThrows, AstUtils.Constant(null, typeof(Exception))),
body,
AstUtils.Empty()
).Catch(
locException,
Expression.Block(
// If there was no except block, or the except block threw, then the
// exception has not yet been properly set, so we need to set the
// currently handled exception when we catch it
Ast.Call(AstMethods.SetCurrentException, Parent.LocalContext, locException),
Ast.Assign(tryThrows, locException),
Expression.Rethrow()
)
)
).FinallyWithJumps(
// if we had an exception save the line # that was last executing during the try
AstUtils.If(
Expression.NotEqual(tryThrows, Expression.Default(typeof(Exception))),
Parent.GetSaveLineNumberExpression(tryThrows, false)
),
// clear the frames incase thae finally throws, and allow line number
// updates to proceed
UpdateLineUpdated(false),
// run the finally code
// if the finally block reraises the same exception we have been handling,
// mark it as already updated
AstUtils.Try(
@finally
).Catch(
locException,
AstUtils.If(
Expression.Equal(locException, tryThrows),
UpdateLineUpdated(true)
),
Expression.Rethrow()
),
// if we took an exception in the try block we have saved the line number. Otherwise
// we have no line number saved and will need to continue saving them if
// other exceptions are thrown.
AstUtils.If(
Expression.NotEqual(tryThrows, Expression.Default(typeof(Exception))),
UpdateLineUpdated(true)
)
);
body = Ast.Block(new[] { tryThrows }, body);
}
return(body);
}
public override MSAst.Expression Reduce()
{
return(GlobalParent.AddDebugInfoAndVoid(AstUtils.Empty(), Span));
}
private MSAst.Expression ReduceWorker(bool optimizeDynamicConvert)
{
MSAst.Expression result;
if (_tests.Length > 100)
{
// generate:
// if(x) {
// body
// goto end
// } else {
// }
// elseBody
// end:
//
// to avoid deeply recursive trees which can stack overflow.
var builder = new ReadOnlyCollectionBuilder <MSAst.Expression>();
var label = Ast.Label();
for (int i = 0; i < _tests.Length; i++)
{
IfStatementTest ist = _tests[i];
builder.Add(
Ast.Condition(
optimizeDynamicConvert ?
TransformAndDynamicConvert(ist.Test, typeof(bool)) :
GlobalParent.Convert(typeof(bool), Microsoft.Scripting.Actions.ConversionResultKind.ExplicitCast, ist.Test),
Ast.Block(
TransformMaybeSingleLineSuite(ist.Body, ist.Test.Start),
Ast.Goto(label)
),
AstUtils.Empty()
)
);
}
if (_else != null)
{
builder.Add(_else);
}
builder.Add(Ast.Label(label));
result = Ast.Block(builder);
}
else
{
// Now build from the inside out
if (_else != null)
{
result = _else;
}
else
{
result = AstUtils.Empty();
}
int i = _tests.Length;
while (i-- > 0)
{
IfStatementTest ist = _tests[i];
result = GlobalParent.AddDebugInfoAndVoid(
Ast.Condition(
optimizeDynamicConvert ?
TransformAndDynamicConvert(ist.Test, typeof(bool)) :
GlobalParent.Convert(typeof(bool), Microsoft.Scripting.Actions.ConversionResultKind.ExplicitCast, ist.Test),
TransformMaybeSingleLineSuite(ist.Body, ist.Test.Start),
result
),
new SourceSpan(ist.Start, ist.Header)
);
}
}
return(result);
}
internal override MSAst.Expression TransformSet(SourceSpan span, MSAst.Expression right, PythonOperationKind op)
{
// if we just have a simple named multi-assignment (e.g. a, b = 1,2)
// then go ahead and step over the entire statement at once. If we have a
// more complex statement (e.g. a.b, c.d = 1, 2) then we'll step over the
// sets individually as they could be property sets the user wants to step
// into. TODO: Enable stepping of the right hand side?
bool emitIndividualSets = false;
foreach (Expression e in _items)
{
if (IsComplexAssignment(e))
{
emitIndividualSets = true;
break;
}
}
SourceSpan rightSpan = SourceSpan.None;
SourceSpan leftSpan =
(Span.Start.IsValid && span.IsValid) ?
new SourceSpan(Span.Start, span.End) :
SourceSpan.None;
SourceSpan totalSpan = SourceSpan.None;
if (emitIndividualSets)
{
rightSpan = span;
leftSpan = SourceSpan.None;
totalSpan = (Span.Start.IsValid && span.IsValid) ?
new SourceSpan(Span.Start, span.End) :
SourceSpan.None;
}
// 1. Evaluate the expression and assign the value to the temp.
MSAst.ParameterExpression right_temp = Ast.Variable(typeof(object), "unpacking");
// 2. Add the assignment "right_temp = right" into the suite/block
MSAst.Expression assignStmt1 = MakeAssignment(right_temp, right);
// 3. Call GetEnumeratorValues on the right side (stored in temp)
MSAst.Expression enumeratorValues = Expression.Convert(LightExceptions.CheckAndThrow(
Expression.Call(
emitIndividualSets ?
AstMethods.GetEnumeratorValues :
AstMethods.GetEnumeratorValuesNoComplexSets, // method
// arguments
Parent.LocalContext,
right_temp,
AstUtils.Constant(_items.Length)
)
), typeof(object[]));
// 4. Create temporary variable for the array
MSAst.ParameterExpression array_temp = Ast.Variable(typeof(object[]), "array");
// 5. Assign the value of the method call (mce) into the array temp
// And add the assignment "array_temp = Ops.GetEnumeratorValues(...)" into the block
MSAst.Expression assignStmt2 = MakeAssignment(
array_temp,
enumeratorValues,
rightSpan
);
ReadOnlyCollectionBuilder <MSAst.Expression> sets = new ReadOnlyCollectionBuilder <MSAst.Expression>(_items.Length + 1);
for (int i = 0; i < _items.Length; i++)
{
// target = array_temp[i]
Expression target = _items[i];
if (target == null)
{
continue;
}
// 6. array_temp[i]
MSAst.Expression element = Ast.ArrayAccess(
array_temp, // array expression
AstUtils.Constant(i) // index
);
// 7. target = array_temp[i], and add the transformed assignment into the list of sets
MSAst.Expression set = target.TransformSet(
emitIndividualSets ? // span
target.Span :
SourceSpan.None,
element,
PythonOperationKind.None
);
sets.Add(set);
}
// 9. add the sets as their own block so they can be marked as a single span, if necessary.
sets.Add(AstUtils.Empty());
MSAst.Expression itemSet = GlobalParent.AddDebugInfo(Ast.Block(sets.ToReadOnlyCollection()), leftSpan);
// 10. Return the suite statement (block)
return(GlobalParent.AddDebugInfo(Ast.Block(new[] { array_temp, right_temp }, assignStmt1, assignStmt2, itemSet, AstUtils.Empty()), totalSpan));
}
protected override Expression VisitTry(TryExpression node)
{
int startYields = _yields.Count;
bool savedInTryWithFinally = _inTryWithFinally;
if (node.Finally != null || node.Fault != null)
{
_inTryWithFinally = true;
}
Expression @try = Visit(node.Body);
int tryYields = _yields.Count;
IList <CatchBlock> handlers = Visit(node.Handlers, VisitCatchBlock);
int catchYields = _yields.Count;
// push a new return label in case the finally block yields
_returnLabels.Push(Expression.Label());
// only one of these can be non-null
Expression @finally = Visit(node.Finally);
Expression fault = Visit(node.Fault);
LabelTarget finallyReturn = _returnLabels.Pop();
int finallyYields = _yields.Count;
_inTryWithFinally = savedInTryWithFinally;
if (@try == node.Body &&
handlers == node.Handlers &&
@finally == node.Finally &&
fault == node.Fault)
{
return(node);
}
// No yields, just return
if (startYields == _yields.Count)
{
return(Expression.MakeTry(null, @try, @finally, fault, handlers));
}
if (fault != null && finallyYields != catchYields)
{
// No one needs this yet, and it's not clear how we should get back to
// the fault
throw new NotSupportedException("yield in fault block is not supported");
}
// If try has yields, we need to build a new try body that
// dispatches to the yield labels
var tryStart = Expression.Label();
if (tryYields != startYields)
{
@try = Expression.Block(MakeYieldRouter(node.Body.Type, startYields, tryYields, tryStart), @try);
}
// Transform catches with yield to deferred handlers
if (catchYields != tryYields)
{
var block = new List <Expression>();
block.Add(MakeYieldRouter(node.Body.Type, tryYields, catchYields, tryStart));
block.Add(null); // empty slot to fill in later
for (int i = 0, n = handlers.Count; i < n; i++)
{
CatchBlock c = handlers[i];
if (c == node.Handlers[i])
{
continue;
}
if (handlers.IsReadOnly)
{
handlers = handlers.ToArray();
}
// the variable that will be scoped to the catch block
var exceptionVar = Expression.Variable(c.Test, null);
// the variable that the catch block body will use to
// access the exception. We reuse the original variable if
// the catch block had one. It needs to be hoisted because
// the catch might contain yields.
var deferredVar = c.Variable ?? Expression.Variable(c.Test, null);
_vars.Add(deferredVar);
// We need to ensure that filters can access the exception
// variable
Expression filter = c.Filter;
if (filter != null && c.Variable != null)
{
filter = Expression.Block(new[] { c.Variable }, Expression.Assign(c.Variable, exceptionVar), filter);
}
// catch (ExceptionType exceptionVar) {
// deferredVar = exceptionVar;
// }
handlers[i] = Expression.Catch(
exceptionVar,
Expression.Block(
Expression.Assign(deferredVar, exceptionVar),
Expression.Default(node.Body.Type)
),
filter
);
// We need to rewrite rethrows into "throw deferredVar"
var catchBody = new RethrowRewriter {
Exception = deferredVar
}.Visit(c.Body);
// if (deferredVar != null) {
// ... catch body ...
// }
block.Add(
Expression.Condition(
Expression.NotEqual(deferredVar, AstUtils.Constant(null, deferredVar.Type)),
catchBody,
Expression.Default(node.Body.Type)
)
);
}
block[1] = Expression.MakeTry(null, @try, null, null, new ReadOnlyCollection <CatchBlock>(handlers));
@try = Expression.Block(block);
handlers = new CatchBlock[0]; // so we don't reuse these
}
if (finallyYields != catchYields)
{
// We need to add a catch block to save the exception, so we
// can rethrow in case there is a yield in the finally. Also,
// add logic for returning. It looks like this:
//
// try { ... } catch (Exception all) { saved = all; }
// finally {
// if (_finallyReturnVar) goto finallyReturn;
// ...
// if (saved != null) throw saved;
// finallyReturn:
// }
// if (_finallyReturnVar) goto _return;
// We need to add a catch(Exception), so if we have catches,
// wrap them in a try
if (handlers.Count > 0)
{
@try = Expression.MakeTry(null, @try, null, null, handlers);
handlers = new CatchBlock[0];
}
// NOTE: the order of these routers is important
// The first call changes the labels to all point at "tryEnd",
// so the second router will jump to "tryEnd"
var tryEnd = Expression.Label();
Expression inFinallyRouter = MakeYieldRouter(node.Body.Type, catchYields, finallyYields, tryEnd);
Expression inTryRouter = MakeYieldRouter(node.Body.Type, catchYields, finallyYields, tryStart);
var all = Expression.Variable(typeof(Exception), "e");
var saved = Expression.Variable(typeof(Exception), "$saved$" + _temps.Count);
_temps.Add(saved);
@try = Expression.Block(
Expression.TryCatchFinally(
Expression.Block(
inTryRouter,
@try,
Expression.Assign(saved, AstUtils.Constant(null, saved.Type)),
Expression.Label(tryEnd)
),
Expression.Block(
MakeSkipFinallyBlock(finallyReturn),
inFinallyRouter,
@finally,
Expression.Condition(
Expression.NotEqual(saved, AstUtils.Constant(null, saved.Type)),
Expression.Throw(saved),
Utils.Empty()
),
Expression.Label(finallyReturn)
),
Expression.Catch(all, Utils.Void(Expression.Assign(saved, all)))
),
Expression.Condition(
Expression.Equal(_gotoRouter, AstUtils.Constant(GotoRouterYielding)),
Expression.Goto(_returnLabels.Peek()),
Utils.Empty()
)
);
@finally = null;
}
else if (@finally != null)
{
// try or catch had a yield, modify finally so we can skip over it
@finally = Expression.Block(
MakeSkipFinallyBlock(finallyReturn),
@finally,
Expression.Label(finallyReturn)
);
}
// Make the outer try, if needed
if (handlers.Count > 0 || @finally != null || fault != null)
{
@try = Expression.MakeTry(null, @try, @finally, fault, handlers);
}
return(Expression.Block(Expression.Label(tryStart), @try));
}
public static Expression Unless(Expression test, Expression body)
{
return(IfThenElse(test, Utils.Empty(), body));
}
internal static MSAst.Expression TransformForStatement(ScopeStatement parent, MSAst.ParameterExpression enumerator,
Expression list, Expression left, MSAst.Expression body,
Statement else_, SourceSpan span, SourceLocation header,
MSAst.LabelTarget breakLabel, MSAst.LabelTarget continueLabel)
{
// enumerator, isDisposable = Dynamic(GetEnumeratorBinder, list)
MSAst.Expression init = Ast.Assign(
enumerator,
parent.GlobalParent.Operation(
typeof(KeyValuePair <IEnumerator, IDisposable>),
PythonOperationKind.GetEnumeratorForIteration,
AstUtils.Convert(list, typeof(object))
)
);
// while enumerator.MoveNext():
// left = enumerator.Current
// body
// else:
// else
MSAst.Expression ls = AstUtils.Loop(
parent.GlobalParent.AddDebugInfo(
Ast.Call(
Ast.Property(
enumerator,
typeof(KeyValuePair <IEnumerator, IDisposable>).GetProperty("Key")
),
typeof(IEnumerator).GetMethod("MoveNext")
),
left.Span
),
null,
Ast.Block(
left.TransformSet(
SourceSpan.None,
Ast.Call(
Ast.Property(
enumerator,
typeof(KeyValuePair <IEnumerator, IDisposable>).GetProperty("Key")
),
typeof(IEnumerator).GetProperty("Current").GetGetMethod()
),
PythonOperationKind.None
),
body,
UpdateLineNumber(list.Start.Line),
AstUtils.Empty()
),
else_,
breakLabel,
continueLabel
);
return(Ast.Block(
init,
Ast.TryFinally(
ls,
Ast.Call(AstMethods.ForLoopDispose, enumerator)
)
));
}
private MSAst.Expression AddFinally(MSAst.Expression /*!*/ body, MSAst.ParameterExpression nestedException)
{
if (_finally != null)
{
Debug.Assert(nestedException != null);
MSAst.ParameterExpression nestedFrames = Ast.Variable(typeof(List <DynamicStackFrame>), "$nestedFrames");
MSAst.Expression @finally = _finally;
// lots is going on here. We need to consider:
// 1. Exceptions propagating out of try/except/finally. Here we need to save the line #
// from the exception block and not save the # from the finally block later.
// 2. Exceptions propagating out of the finally block. Here we need to report the line number
// from the finally block and leave the existing stack traces cleared.
// 3. Returning from the try block: Here we need to run the finally block and not update the
// line numbers.
body = AstUtils.Try( // we use a fault to know when we have an exception and when control leaves normally (via
// either a return or the body completing successfully).
AstUtils.Try(
Parent.AddDebugInfo(AstUtils.Empty(), new SourceSpan(Span.Start, _header)),
Ast.Assign(nestedException, AstUtils.Constant(false)),
body
).Fault(
// fault
Ast.Assign(nestedException, AstUtils.Constant(true))
)
).FinallyWithJumps(
// if we had an exception save the line # that was last executing during the try
AstUtils.If(
nestedException,
Parent.GetSaveLineNumberExpression(false)
),
// clear the frames incase thae finally throws, and allow line number
// updates to proceed
UpdateLineUpdated(false),
Ast.Assign(
nestedFrames,
Ast.Call(AstMethods.GetAndClearDynamicStackFrames)
),
// run the finally code
@finally,
// if the finally exits normally restore any previous exception info
Ast.Call(
AstMethods.SetDynamicStackFrames,
nestedFrames
),
// if we took an exception in the try block we have saved the line number. Otherwise
// we have no line number saved and will need to continue saving them if
// other exceptions are thrown.
AstUtils.If(
nestedException,
UpdateLineUpdated(true)
)
);
body = Ast.Block(new[] { nestedFrames }, body);
}
return(body);
}
/// <summary>
/// WithStatement is translated to the DLR AST equivalent to
/// the following Python code snippet (from with statement spec):
///
/// mgr = (EXPR)
/// exit = mgr.__exit__ # Not calling it yet
/// value = mgr.__enter__()
/// exc = True
/// try:
/// VAR = value # Only if "as VAR" is present
/// BLOCK
/// except:
/// # The exceptional case is handled here
/// exc = False
/// if not exit(*sys.exc_info()):
/// raise
/// # The exception is swallowed if exit() returns true
/// finally:
/// # The normal and non-local-goto cases are handled here
/// if exc:
/// exit(None, None, None)
///
/// </summary>
public override MSAst.Expression Reduce()
{
// Five statements in the result...
ReadOnlyCollectionBuilder <MSAst.Expression> statements = new ReadOnlyCollectionBuilder <MSAst.Expression>(6);
ReadOnlyCollectionBuilder <MSAst.ParameterExpression> variables = new ReadOnlyCollectionBuilder <MSAst.ParameterExpression>(6);
MSAst.ParameterExpression lineUpdated = Ast.Variable(typeof(bool), "$lineUpdated_with");
variables.Add(lineUpdated);
//******************************************************************
// 1. mgr = (EXPR)
//******************************************************************
MSAst.ParameterExpression manager = Ast.Variable(typeof(object), "with_manager");
variables.Add(manager);
statements.Add(
GlobalParent.AddDebugInfo(
Ast.Assign(
manager,
_contextManager
),
new SourceSpan(GlobalParent.IndexToLocation(StartIndex), GlobalParent.IndexToLocation(_headerIndex))
)
);
//******************************************************************
// 2. exit = mgr.__exit__ # Not calling it yet
//******************************************************************
MSAst.ParameterExpression exit = Ast.Variable(typeof(object), "with_exit");
variables.Add(exit);
statements.Add(
MakeAssignment(
exit,
GlobalParent.Get(
"__exit__",
manager
)
)
);
//******************************************************************
// 3. value = mgr.__enter__()
//******************************************************************
MSAst.ParameterExpression value = Ast.Variable(typeof(object), "with_value");
variables.Add(value);
statements.Add(
GlobalParent.AddDebugInfoAndVoid(
MakeAssignment(
value,
Parent.Invoke(
new CallSignature(0),
Parent.LocalContext,
GlobalParent.Get(
"__enter__",
manager
)
)
),
new SourceSpan(GlobalParent.IndexToLocation(StartIndex), GlobalParent.IndexToLocation(_headerIndex))
)
);
//******************************************************************
// 4. exc = True
//******************************************************************
MSAst.ParameterExpression exc = Ast.Variable(typeof(bool), "with_exc");
variables.Add(exc);
statements.Add(
MakeAssignment(
exc,
AstUtils.Constant(true)
)
);
//******************************************************************
// 5. The final try statement:
//
// try:
// VAR = value # Only if "as VAR" is present
// BLOCK
// except:
// # The exceptional case is handled here
// exc = False
// if not exit(*sys.exc_info()):
// raise
// # The exception is swallowed if exit() returns true
// finally:
// # The normal and non-local-goto cases are handled here
// if exc:
// exit(None, None, None)
//******************************************************************
MSAst.ParameterExpression exception;
statements.Add(
// try:
AstUtils.Try(
AstUtils.Try(// try statement body
PushLineUpdated(false, lineUpdated),
_var != null ?
(MSAst.Expression)Ast.Block(
// VAR = value
_var.TransformSet(SourceSpan.None, value, PythonOperationKind.None),
// BLOCK
_body,
AstUtils.Empty()
) :
// BLOCK
(MSAst.Expression)_body // except:, // try statement location
).Catch(exception = Ast.Variable(typeof(Exception), "exception"),
// Python specific exception handling code
TryStatement.GetTracebackHeader(
this,
exception,
GlobalParent.AddDebugInfoAndVoid(
Ast.Block(
// exc = False
MakeAssignment(
exc,
AstUtils.Constant(false)
),
// if not exit(*sys.exc_info()):
// raise
AstUtils.IfThen(
GlobalParent.Convert(
typeof(bool),
ConversionResultKind.ExplicitCast,
GlobalParent.Operation(
typeof(bool),
PythonOperationKind.IsFalse,
MakeExitCall(exit, exception)
)
),
UpdateLineUpdated(true),
Ast.Throw(
Ast.Call(
AstMethods.MakeRethrowExceptionWorker,
exception
)
)
)
),
_body.Span
)
),
PopLineUpdated(lineUpdated),
Ast.Empty()
)
// finally:
).Finally(
// if exc:
// exit(None, None, None)
AstUtils.IfThen(
exc,
GlobalParent.AddDebugInfoAndVoid(
Ast.Block(
MSAst.DynamicExpression.Dynamic(
GlobalParent.PyContext.Invoke(
new CallSignature(3) // signature doesn't include function
),
typeof(object),
new MSAst.Expression[] {
Parent.LocalContext,
exit,
AstUtils.Constant(null),
AstUtils.Constant(null),
AstUtils.Constant(null)
}
),
Ast.Empty()
),
_contextManager.Span
)
)
)
);
statements.Add(AstUtils.Empty());
return(Ast.Block(variables.ToReadOnlyCollection(), statements.ToReadOnlyCollection()));
}
public override MSAst.Expression Reduce()
{
if (_names == _star)
{
// from a[.b] import *
return(GlobalParent.AddDebugInfo(
Ast.Call(
AstMethods.ImportStar,
Parent.LocalContext,
AstUtils.Constant(_root.MakeString()),
AstUtils.Constant(GetLevel())
),
Span
));
}
else
{
// from a[.b] import x [as xx], [ y [ as yy] ] [ , ... ]
ReadOnlyCollectionBuilder <MSAst.Expression> statements = new ReadOnlyCollectionBuilder <MSAst.Expression>();
MSAst.ParameterExpression module = Ast.Variable(typeof(object), "module");
// Create initializer of the array of names being passed to ImportWithNames
MSAst.Expression[] names = new MSAst.Expression[_names.Length];
for (int i = 0; i < names.Length; i++)
{
names[i] = AstUtils.Constant(_names[i]);
}
// module = PythonOps.ImportWithNames(<context>, _root, make_array(_names))
statements.Add(
GlobalParent.AddDebugInfoAndVoid(
AssignValue(
module,
LightExceptions.CheckAndThrow(
Expression.Call(
AstMethods.ImportWithNames,
Parent.LocalContext,
AstUtils.Constant(_root.MakeString()),
Ast.NewArrayInit(typeof(string), names),
AstUtils.Constant(GetLevel())
)
)
),
_root.Span
)
);
// now load all the names being imported and assign the variables
for (int i = 0; i < names.Length; i++)
{
statements.Add(
GlobalParent.AddDebugInfoAndVoid(
AssignValue(
Parent.GetVariableExpression(_variables[i]),
Ast.Call(
AstMethods.ImportFrom,
Parent.LocalContext,
module,
names[i]
)
),
Span
)
);
}
statements.Add(AstUtils.Empty());
return(GlobalParent.AddDebugInfo(Ast.Block(new[] { module }, statements.ToArray()), Span));
}
}
public override MSAst.Expression Reduce()
{
// allocated all variables here so they won't be shared w/ other
// locals allocated during the body or except blocks.
MSAst.ParameterExpression lineUpdated = null;
MSAst.ParameterExpression runElse = null;
if (_else != null || (_handlers != null && _handlers.Length > 0))
{
lineUpdated = Ast.Variable(typeof(bool), "$lineUpdated_try");
if (_else != null)
{
runElse = Ast.Variable(typeof(bool), "run_else");
}
}
// don't allocate locals below here...
MSAst.Expression body = _body;
MSAst.Expression @else = _else;
MSAst.Expression @catch, result;
MSAst.ParameterExpression exception;
if (_handlers != null && _handlers.Length > 0)
{
exception = Ast.Variable(typeof(Exception), "$exception");
@catch = TransformHandlers(exception);
}
else
{
exception = null;
@catch = null;
}
// We have else clause, must generate guard around it
if (@else != null)
{
Debug.Assert(@catch != null);
// run_else = true;
// try {
// try_body
// } catch ( ... ) {
// run_else = false;
// catch_body
// }
// if (run_else) {
// else_body
// }
result =
Ast.Block(
Ast.Assign(runElse, AstUtils.Constant(true)),
// save existing line updated, we could choose to do this only for nested exception handlers.
PushLineUpdated(false, lineUpdated),
AstUtils.Try(
Parent.AddDebugInfo(AstUtils.Empty(), new SourceSpan(Span.Start, _header)),
body
).Catch(exception,
Ast.Assign(runElse, AstUtils.Constant(false)),
@catch,
// restore existing line updated after exception handler completes
PopLineUpdated(lineUpdated),
Ast.Assign(exception, Ast.Constant(null, typeof(Exception))),
AstUtils.Default(body.Type)
),
AstUtils.IfThen(runElse,
@else
),
AstUtils.Empty()
);
}
else if (@catch != null) // no "else" clause
// try {
// <try body>
// } catch (Exception e) {
// ... catch handling ...
// }
//
{
result =
AstUtils.Try(
GlobalParent.AddDebugInfo(AstUtils.Empty(), new SourceSpan(Span.Start, _header)),
// save existing line updated
PushLineUpdated(false, lineUpdated),
body
).Catch(exception,
@catch,
// restore existing line updated after exception handler completes
PopLineUpdated(lineUpdated),
Ast.Call(AstMethods.ExceptionHandled, Parent.LocalContext),
Ast.Assign(exception, Ast.Constant(null, typeof(Exception))),
AstUtils.Default(body.Type)
);
}
else
{
result = body;
}
return(Ast.Block(
GetVariables(lineUpdated, runElse),
AddFinally(result)
));
}
public override MSAst.Expression Reduce()
{
// global statement is Python's specific syntactic sugar.
return(AstUtils.Empty());
}
protected override Expression VisitTry(TryExpression node)
{
// Visit finally/fault block first
BlockInfo block = new BlockInfo {
InFinally = true
};
_blocks.Push(block);
Expression @finally = Visit(node.Finally);
Expression fault = Visit(node.Fault);
block.InFinally = false;
LabelTarget finallyEnd = block.FlowLabel;
if (finallyEnd != null)
{
// Make a new target, which will be emitted after the try
block.FlowLabel = Expression.Label();
}
Expression @try = Visit(node.Body);
IList <CatchBlock> handlers = Visit(node.Handlers, VisitCatchBlock);
_blocks.Pop();
if (@try == node.Body &&
handlers == node.Handlers &&
@finally == node.Finally &&
fault == node.Fault)
{
return(node);
}
if (!block.HasFlow)
{
return(Expression.MakeTry(null, @try, @finally, fault, handlers));
}
if (node.Type != typeof(void))
{
// This is not hard to support in principle, but not needed by anyone yet.
throw new NotSupportedException("FinallyFlowControlExpression does not support TryExpressions of non-void type.");
}
// If there is a control flow in finally, emit outer:
// try {
// // try block body and all catch handling
// } catch (Exception all) {
// saved = all;
// } finally {
// finally_body
// if (saved != null) {
// throw saved;
// }
// }
//
// If we have a fault handler we turn this into the better:
// try {
// // try block body and all catch handling
// } catch (Exception all) {
// fault_body
// throw all
// }
if (handlers.Count > 0)
{
@try = Expression.MakeTry(null, @try, null, null, handlers);
}
var saved = Expression.Variable(typeof(Exception), "$exception");
var all = Expression.Variable(typeof(Exception), "e");
if (@finally != null)
{
handlers = new[] {
Expression.Catch(
all,
Expression.Block(
Expression.Assign(saved, all),
Utils.Default(node.Type)
)
)
};
@finally = Expression.Block(
@finally,
Expression.Condition(
Expression.NotEqual(saved, AstUtils.Constant(null, saved.Type)),
Expression.Throw(saved),
Utils.Empty()
)
);
if (finallyEnd != null)
{
@finally = Expression.Label(finallyEnd, @finally);
}
}
else
{
Debug.Assert(fault != null);
fault = Expression.Block(fault, Expression.Throw(all));
if (finallyEnd != null)
{
fault = Expression.Label(finallyEnd, fault);
}
handlers = new[] { Expression.Catch(all, fault) };
fault = null;
}
// Emit flow control
return(Expression.Block(
new[] { saved },
Expression.MakeTry(null, @try, @finally, fault, handlers),
Expression.Label(block.FlowLabel),
MakeFlowControlSwitch(block)
));
}
private MSA.Expression /*!*/ TransformExceptionHandling(AstGenerator /*!*/ gen, ResultOperation resultOperation)
{
Assert.NotNull(gen);
MSA.Expression exceptionThrownVariable = gen.CurrentScope.DefineHiddenVariable("#exception-thrown", typeof(bool));
MSA.Expression exceptionRethrowVariable = gen.CurrentScope.DefineHiddenVariable("#exception-rethrow", typeof(bool));
MSA.Expression retryingVariable = gen.CurrentScope.DefineHiddenVariable("#retrying", typeof(bool));
MSA.Expression oldExceptionVariable = gen.CurrentScope.DefineHiddenVariable("#old-exception", typeof(Exception));
MSA.ParameterExpression unwinder, exceptionVariable;
MSA.Expression transformedBody;
MSA.Expression transformedEnsure;
MSA.Expression transformedElse;
if (_ensureStatements != null)
{
transformedEnsure = Ast.Block(
// ensure:
Ast.Assign(oldExceptionVariable, Methods.GetCurrentException.OpCall(gen.CurrentScopeVariable)),
gen.TransformStatements(_ensureStatements, ResultOperation.Ignore),
Methods.SetCurrentException.OpCall(gen.CurrentScopeVariable, oldExceptionVariable),
// rethrow:
AstUtils.IfThen(
Ast.AndAlso(
exceptionRethrowVariable,
Ast.NotEqual(oldExceptionVariable, AstUtils.Constant(null))
),
Ast.Throw(oldExceptionVariable)
)
);
}
else
{
// rethrow:
transformedEnsure = AstUtils.IfThen(
Ast.AndAlso(
exceptionRethrowVariable,
Ast.NotEqual(
Ast.Assign(oldExceptionVariable, Methods.GetCurrentException.OpCall(gen.CurrentScopeVariable)),
AstUtils.Constant(null, typeof(Exception)))
),
Ast.Throw(oldExceptionVariable)
);
}
if (_elseStatements != null)
{
transformedElse = gen.TransformStatements(_elseStatements, resultOperation);
}
else
{
transformedElse = AstUtils.Empty();
}
// body should do return, but else-clause is present => we cannot do return from the guarded statements:
// (the value of the last expression in the body cannot be the last executed expression statement => we can ignore it):
transformedBody = gen.TransformStatements(_statements, (_elseStatements != null) ? ResultOperation.Ignore : resultOperation);
MSA.Expression enterRescue = null, leaveRescue = null;
var retryLabel = Ast.Label("retry");
// make rescue clause:
MSA.Expression transformedRescue;
if (_rescueClauses != null)
{
// outer-most EH blocks sets and clears runtime flag RuntimeFlowControl.InTryRescue:
if (gen.CurrentRescue == null)
{
enterRescue = Methods.EnterRescue.OpCall(gen.CurrentScopeVariable);
leaveRescue = Methods.LeaveRescue.OpCall(gen.CurrentScopeVariable);
}
else
{
enterRescue = leaveRescue = AstUtils.Empty();
}
gen.EnterRescueClause(retryingVariable, retryLabel);
var handlers = new IfStatementTest[_rescueClauses.Count];
for (int i = 0; i < handlers.Length; i++)
{
handlers[i] = _rescueClauses[i].Transform(gen, resultOperation);
}
transformedRescue =
AstUtils.Try(
enterRescue,
AstUtils.If(handlers, Ast.Assign(exceptionRethrowVariable, AstUtils.Constant(true)))
).Filter(unwinder = Ast.Parameter(typeof(EvalUnwinder), "#u"),
Ast.Equal(Ast.Field(unwinder, EvalUnwinder.ReasonField), AstUtils.Constant(BlockReturnReason.Retry)),
Ast.Block(
Ast.Assign(retryingVariable, AstUtils.Constant(true)),
Ast.Continue(retryLabel),
AstUtils.Empty()
)
);
gen.LeaveRescueClause();
}
else
{
transformedRescue = Ast.Assign(exceptionRethrowVariable, AstUtils.Constant(true));
}
if (_elseStatements != null)
{
transformedElse = AstUtils.Unless(exceptionThrownVariable, transformedElse);
}
var result = Ast.Block(
Ast.Label(retryLabel),
AstUtils.Try(
Ast.Assign(exceptionThrownVariable, AstUtils.Constant(false)),
Ast.Assign(exceptionRethrowVariable, AstUtils.Constant(false)),
Ast.Assign(retryingVariable, AstUtils.Constant(false)),
// save exception (old_$! is not used unless there is a rescue clause):
(_rescueClauses == null) ? (MSA.Expression)AstUtils.Empty() :
Ast.Assign(oldExceptionVariable, Methods.GetCurrentException.OpCall(gen.CurrentScopeVariable)),
AstUtils.Try(
Ast.Block(transformedBody, AstUtils.Empty())
).Filter(exceptionVariable = Ast.Parameter(typeof(Exception), "#e"),
Methods.CanRescue.OpCall(gen.CurrentScopeVariable, exceptionVariable),
Ast.Assign(exceptionThrownVariable, AstUtils.Constant(true)),
transformedRescue,
AstUtils.Empty()
).FinallyIf((_rescueClauses != null),
// restore previous exception if the current one has been handled:
AstUtils.Unless(exceptionRethrowVariable,
Methods.SetCurrentException.OpCall(gen.CurrentScopeVariable, oldExceptionVariable)
),
leaveRescue
),
// unless (exception_thrown) do <else-statements> end
transformedElse,
AstUtils.Empty()
).FilterIf((_rescueClauses != null || _elseStatements != null),
exceptionVariable = Ast.Parameter(typeof(Exception), "#e"),
Methods.CanRescue.OpCall(gen.CurrentScopeVariable, exceptionVariable),
Ast.Assign(exceptionRethrowVariable, AstUtils.Constant(true)),
AstUtils.Empty()
).FinallyWithJumps(
AstUtils.Unless(retryingVariable, transformedEnsure)
)
);
return(result);
}
public static LoopExpression Loop(Expression test, Expression increment, Expression body, Expression @else, LabelTarget @break, LabelTarget @continue)
{
ContractUtils.RequiresNotNull(body, "body");
if (test != null)
{
ContractUtils.Requires(test.Type == typeof(bool), "test", "Test must be boolean");
if (@break == null)
{
@break = Expression.Label();
}
}
// for (;;) {
// if (test) {
// } else {
// else;
// break;
// }
// Body
// continue:
// Increment;
// }
// If there is no test, 'else' will never execute and gets simply thrown away.
return(Expression.Loop(
Expression.Block(
test != null
? (Expression)Expression.Condition(
test,
Utils.Empty(),
Expression.Block(
@else != null ? @else : Utils.Empty(),
Expression.Break(@break)
)
)
: Utils.Empty(),
body,
@continue != null ? (Expression)Expression.Label(@continue) : Utils.Empty(),
increment != null ? increment : Utils.Empty()
),
@break,
null
));
}
public override MSAst.Expression Reduce()
{
// allocated all variables here so they won't be shared w/ other
// locals allocated during the body or except blocks.
MSAst.ParameterExpression?lineUpdated = null;
MSAst.ParameterExpression?runElse = null;
MSAst.ParameterExpression?previousExceptionContext = null;
Debug.Assert(Else is null || _handlers.Length > 0);
if (_handlers.Length > 0)
{
lineUpdated = Ast.Variable(typeof(bool), "$lineUpdated_try");
if (Else != null)
{
runElse = Ast.Variable(typeof(bool), "run_else");
}
}
// don't allocate locals below here...
MSAst.Expression body = Body;
MSAst.Expression? @else = Else;
MSAst.Expression? @catch;
MSAst.Expression result;
MSAst.ParameterExpression?exception;
if (_handlers.Length > 0)
{
previousExceptionContext = Ast.Variable(typeof(Exception), "$previousException");
exception = Ast.Variable(typeof(Exception), "$exception");
@catch = TransformHandlers(exception, previousExceptionContext);
}
else if (Finally != null)
{
exception = Ast.Variable(typeof(Exception), "$exception");
@catch = null;
}
else
{
exception = null;
@catch = null;
}
// We have else clause, must generate guard around it
if (@else != null)
{
Debug.Assert(runElse != null);
Debug.Assert(previousExceptionContext != null && exception != null && @catch != null);
// run_else = true;
// try {
// try_body
// } catch ( ... ) {
// run_else = false;
// catch_body
// }
// if (run_else) {
// else_body
// }
result =
Ast.Block(
Ast.Assign(runElse, AstUtils.Constant(true)),
// save existing line updated, we could choose to do this only for nested exception handlers.
PushLineUpdated(false, lineUpdated),
LightExceptions.RewriteExternal(
AstUtils.Try(
Parent.AddDebugInfo(AstUtils.Empty(), new SourceSpan(Span.Start, GlobalParent.IndexToLocation(HeaderIndex))),
Ast.Assign(previousExceptionContext, Ast.Call(AstMethods.SaveCurrentException)),
body,
AstUtils.Constant(null)
).Catch(exception,
Ast.Assign(runElse, AstUtils.Constant(false)),
@catch,
// restore existing line updated after exception handler completes
PopLineUpdated(lineUpdated),
Ast.Assign(exception, Ast.Constant(null, typeof(Exception))),
AstUtils.Constant(null)
)
),
AstUtils.IfThen(runElse,
@else
),
AstUtils.Empty()
);
}
else if (@catch != null) // no "else" clause
// try {
// <try body>
// } catch (Exception e) {
// ... catch handling ...
// }
//
{
Debug.Assert(previousExceptionContext != null && exception != null);
result =
LightExceptions.RewriteExternal(
AstUtils.Try(
GlobalParent.AddDebugInfo(AstUtils.Empty(), new SourceSpan(Span.Start, GlobalParent.IndexToLocation(HeaderIndex))),
// save existing line updated
PushLineUpdated(false, lineUpdated),
Ast.Assign(previousExceptionContext, Ast.Call(AstMethods.SaveCurrentException)),
body,
AstUtils.Constant(null)
).Catch(exception,
@catch,
// restore existing line updated after exception handler completes
PopLineUpdated(lineUpdated),
Ast.Assign(exception, Ast.Constant(null, typeof(Exception))),
AstUtils.Constant(null)
)
);
}
else
{
result = body;
}
return(Ast.Block(
GetVariables(lineUpdated, runElse, previousExceptionContext),
AddFinally(result),
AstUtils.Default(typeof(void))
));
}