internal override MSAst.Expression TransformSet(AstGenerator ag, 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 = ag.GetTemporary("unpacking");
// 2. Add the assignment "right_temp = right" into the suite/block
MSAst.Expression assignStmt1 = AstGenerator.MakeAssignment(right_temp, right);
// 3. Call GetEnumeratorValues on the right side (stored in temp)
MSAst.Expression enumeratorValues = Ast.Call(
AstGenerator.GetHelperMethod("GetEnumeratorValues"), // method
// arguments
ag.LocalContext,
right_temp,
AstUtils.Constant(_items.Length)
);
// 4. Create temporary variable for the array
MSAst.ParameterExpression array_temp = ag.GetTemporary("array", typeof(object[]));
// 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 = ag.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(
ag,
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 = ag.AddDebugInfo(Ast.Block(sets.ToReadOnlyCollection()), leftSpan);
// 10. Free the temps
ag.FreeTemp(array_temp);
ag.FreeTemp(right_temp);
// 11. Return the suite statement (block)
return ag.AddDebugInfo(Ast.Block(assignStmt1, assignStmt2, itemSet, AstUtils.Empty()), totalSpan);
}
/// <summary>
/// Transform multiple python except handlers for a try block into a single catch body.
/// </summary>
/// <param name="ag"></param>
/// <param name="variable">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(AstGenerator ag, out MSAst.ParameterExpression variable) {
if (_handlers == null || _handlers.Length == 0) {
variable = null;
return null;
}
MSAst.ParameterExpression exception = ag.GetTemporary("exception", typeof(Exception));
MSAst.ParameterExpression extracted = ag.GetTemporary("extracted", typeof(object));
// The variable where the runtime will store the exception.
variable = exception;
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(
AstGenerator.GetHelperMethod("CheckException"),
extracted,
ag.TransformAsObject(tsh.Test)
);
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 = ag.GetTemporary("converted");
}
ist = AstUtils.IfCondition(
Ast.NotEqual(
Ast.Assign(converted, test),
Ast.Constant(null)
),
Ast.Block(
tsh.Target.TransformSet(ag, SourceSpan.None, converted, Operators.None),
GetTracebackHeader(
new SourceSpan(tsh.Start, tsh.Header),
ag,
exception,
ag.Transform(tsh.Body)
),
Ast.Empty()
)
);
} else {
// translating:
// except Test:
// <body>
// into:
// if (CheckException(exception, Test) != null) {
// traceback-header
// <body>
// }
ist = AstUtils.IfCondition(
Ast.NotEqual(
test,
Ast.Constant(null)
),
GetTracebackHeader(
new SourceSpan(tsh.Start, tsh.Header),
ag,
exception,
ag.Transform(tsh.Body)
)
);
}
// 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 = GetTracebackHeader(new SourceSpan(tsh.Start, tsh.Header), ag, exception, ag.Transform(tsh.Body));
}
}
MSAst.Expression body = null;
if (tests.Count > 0) {
// rethrow the exception if we have no catch-all block
if (catchAll == null) {
catchAll = Ast.Throw(exception);
}
body = AstUtils.If(
tests.ToArray(),
catchAll
);
} else {
Debug.Assert(catchAll != null);
body = catchAll;
}
if (converted != null) {
ag.FreeTemp(converted);
}
ag.FreeTemp(exception);
ag.FreeTemp(extracted);
// Codegen becomes:
// extracted = PythonOps.SetCurrentException(exception)
// < dynamic exception analysis >
return Ast.Block(
Ast.Assign(
extracted,
Ast.Call(
AstGenerator.GetHelperMethod("SetCurrentException"),
AstUtils.CodeContext(),
exception
)
),
body,
Ast.Empty()
);
}
internal override MSAst.Expression Transform(AstGenerator ag) {
// allocated all variables here so they won't be shared w/ other
// locals allocated during the body or except blocks.
MSAst.ParameterExpression noNestedException = null;
if (_finally != null) {
noNestedException = ag.GetTemporary("$noException", typeof(bool));
}
MSAst.ParameterExpression lineUpdated = null;
MSAst.ParameterExpression runElse = null;
if (_else != null || (_handlers != null && _handlers.Length > 0)) {
lineUpdated = ag.GetTemporary("$lineUpdated", typeof(bool));
if (_else != null) {
runElse = ag.GetTemporary("run_else", typeof(bool));
}
}
// don't allocate locals below here...
MSAst.Expression body = ag.Transform(_body);
MSAst.Expression @else = ag.Transform(_else);
if (body == null) {
return null;
}
MSAst.ParameterExpression exception;
MSAst.Expression @catch = TransformHandlers(ag, out exception);
MSAst.Expression result;
// 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, Ast.Constant(true)),
// save existing line updated, we could choose to do this only for nested exception handlers.
ag.PushLineUpdated(false, lineUpdated),
AstUtils.Try(
ag.AddDebugInfo(Ast.Empty(), new SourceSpan(Span.Start, _header)),
body
).Catch(exception,
Ast.Assign(runElse, Ast.Constant(false)),
@catch,
// restore existing line updated after exception handler completes
ag.PopLineUpdated(lineUpdated),
Ast.Default(body.Type)
),
AstUtils.IfThen(runElse,
@else
),
Ast.Empty()
);
} else if (@catch != null) { // no "else" clause
// try {
// <try body>
// } catch (Exception e) {
// ... catch handling ...
// }
//
result = AstUtils.Try(
ag.AddDebugInfo(Ast.Empty(), new SourceSpan(Span.Start, _header)),
// save existing line updated
ag.PushLineUpdated(false, lineUpdated),
body
).Catch(exception,
@catch,
// restore existing line updated after exception handler completes
ag.PopLineUpdated(lineUpdated),
Ast.Default(body.Type)
);
} else {
result = body;
}
try {
return AddFinally(ag, result, noNestedException);
} finally {
// free all locals here after the children nodes have been generated
if (lineUpdated != null) {
ag.FreeTemp(lineUpdated);
}
if (runElse != null) {
ag.FreeTemp(@runElse);
}
}
}
private MSAst.Expression AddFinally(AstGenerator/*!*/ ag, MSAst.Expression/*!*/ body, MSAst.ParameterExpression noNestedException) {
if (_finally != null) {
Debug.Assert(noNestedException != null);
MSAst.ParameterExpression nestedFrames = ag.GetTemporary("$nestedFrames", typeof(List<DynamicStackFrame>));
bool inFinally = ag.InFinally;
ag.InFinally = true;
MSAst.Expression @finally = ag.Transform(_finally);
ag.InFinally = inFinally;
if (@finally == null) {
// error reported during compilation
return null;
}
if (ag.TrackLines) {
// 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 filter to know when we have an exception and when control leaves normally (via
// either a return or the body completing successfully).
AstUtils.Try(
ag.AddDebugInfo(Ast.Empty(), new SourceSpan(Span.Start, _header)),
Ast.Assign(noNestedException, Ast.Constant(true)),
body
).Filter(
typeof(Exception),
// condition is never true, just note the exception and let it propagate
Ast.Equal(
Ast.Assign(noNestedException, Ast.Constant(false)),
Ast.Constant(true)
),
Ast.Default(body.Type)
)
).Finally(
// if we had an exception save the line # that was last executing during the try
AstUtils.If(
Ast.Not(noNestedException),
ag.GetLineNumberUpdateExpression(false)
),
// clear the frames incase thae finally throws, and allow line number
// updates to proceed
ag.UpdateLineUpdated(false),
Ast.Assign(
nestedFrames,
Ast.Call(AstGenerator.GetHelperMethod("GetAndClearDynamicStackFrames"))
),
// run the finally code
@finally,
// if the finally exits normally restore any previous exception info
Ast.Call(
AstGenerator.GetHelperMethod("SetDynamicStackFrames"),
nestedFrames
),
ag.UpdateLineUpdated(true)
);
ag.FreeTemp(nestedFrames);
ag.FreeTemp(noNestedException);
} else {
body = AstUtils.Try(body).Finally(
Ast.Assign(
nestedFrames,
Ast.Call(AstGenerator.GetHelperMethod("GetAndClearDynamicStackFrames"))
),
// run the finally code
@finally,
// if the finally exits normally restore any previous exception info
Ast.Call(
AstGenerator.GetHelperMethod("SetDynamicStackFrames"),
nestedFrames
)
);
}
}
return body;
}
private MSAst.Expression AddFinally(AstGenerator/*!*/ ag, MSAst.Expression/*!*/ body, MSAst.ParameterExpression nestedException) {
if (_finally != null) {
bool isEmitting = ag._isEmittingFinally;
ag._isEmittingFinally = true;
int loopId = ++ag._loopOrFinallyId;
ag.LoopOrFinallyIds.Add(loopId, true);
try {
Debug.Assert(nestedException != null);
MSAst.ParameterExpression nestedFrames = ag.GetTemporary("$nestedFrames", typeof(List<DynamicStackFrame>));
bool inFinally = ag.InFinally;
ag.InFinally = true;
MSAst.Expression @finally = ag.Transform(_finally);
ag.InFinally = inFinally;
if (@finally == null) {
// error reported during compilation
return null;
}
// 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(
ag.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,
ag.GetSaveLineNumberExpression(false)
),
// clear the frames incase thae finally throws, and allow line number
// updates to proceed
ag.UpdateLineUpdated(false),
Ast.Assign(
nestedFrames,
Ast.Call(AstGenerator.GetHelperMethod("GetAndClearDynamicStackFrames"))
),
// run the finally code
@finally,
// if the finally exits normally restore any previous exception info
Ast.Call(
AstGenerator.GetHelperMethod("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,
ag.UpdateLineUpdated(true)
)
);
ag.FreeTemp(nestedFrames);
ag.FreeTemp(nestedException);
} finally {
ag._isEmittingFinally = isEmitting;
ag.LoopOrFinallyIds.Remove(loopId);
}
}
return body;
}
// This is a compound comparison operator like: a < b < c.
// That's represented as binary operators, but it's not the same as (a<b) < c, so we do special transformations.
// We need to:
// - return true iff (a<b) && (b<c), but ensure that b is only evaluated once.
// - ensure evaluation order is correct (a,b,c)
// - don't evaluate c if a<b is false.
private MSAst.Expression FinishCompare(MSAst.Expression left, AstGenerator ag) {
Debug.Assert(_right is BinaryExpression);
BinaryExpression bright = (BinaryExpression)_right;
// Transform the left child of my right child (the next node in sequence)
MSAst.Expression rleft = ag.Transform(bright.Left);
// Store it in the temp
MSAst.ParameterExpression temp = ag.GetTemporary("chained_comparison");
// Create binary operation: left <_op> (temp = rleft)
MSAst.Expression comparison = MakeBinaryOperation(
ag,
_op,
left,
Ast.Assign(temp, AstUtils.Convert(rleft, temp.Type)),
typeof(object),
Span
);
MSAst.Expression rright;
// Transform rright, comparing to temp
if (IsComparison(bright._right)) {
rright = bright.FinishCompare(temp, ag);
} else {
MSAst.Expression transformedRight = ag.Transform(bright.Right);
rright = MakeBinaryOperation(
ag,
bright.Operator,
temp,
transformedRight,
typeof(object),
bright.Span
);
}
ag.FreeTemp(temp);
// return (left (op) (temp = rleft)) and (rright)
return AstUtils.CoalesceTrue(
ag.Block,
comparison,
rright,
AstGenerator.GetHelperMethod("IsTrue")
);
}
internal override MSAst.Expression TransformSet(AstGenerator ag, SourceSpan span, MSAst.Expression right, Operators op) {
if (op != Operators.None) {
ag.AddError("augmented assign to sequence prohibited", Span);
return null;
}
// 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;
}
MSAst.Expression[] statements = new MSAst.Expression[4];
// 1. Evaluate the expression and assign the value to the temp.
MSAst.ParameterExpression right_temp = ag.GetTemporary("unpacking");
// 2. Add the assignment "right_temp = right" into the suite/block
statements[0] = ag.MakeAssignment(right_temp, right);
// 3. Call GetEnumeratorValues on the right side (stored in temp)
MSAst.Expression enumeratorValues = Ast.Call(
AstGenerator.GetHelperMethod("GetEnumeratorValues"), // method
// arguments
AstUtils.CodeContext(),
right_temp,
Ast.Constant(_items.Length)
);
// 4. Create temporary variable for the array
MSAst.ParameterExpression array_temp = ag.GetTemporary("array", typeof(object[]));
// 5. Assign the value of the method call (mce) into the array temp
// And add the assignment "array_temp = Ops.GetEnumeratorValues(...)" into the block
statements[1] = ag.MakeAssignment(
array_temp,
enumeratorValues,
rightSpan
);
MSAst.Expression[] sets = new 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
Ast.Constant(i) // index
);
// 7. target = array_temp[i], and add the transformed assignment into the list of sets
MSAst.Expression set = target.TransformSet(
ag,
emitIndividualSets ? // span
target.Span :
SourceSpan.None,
element,
Operators.None
);
if (set == null) {
throw PythonOps.SyntaxError(string.Format("can't assign to {0}", target.NodeName), ag.Context.SourceUnit, target.Span, -1);
}
sets[i] = set;
}
// 9. add the sets as their own block so they can be marked as a single span, if necessary.
sets[_items.Length] = Ast.Empty();
statements[2] = ag.AddDebugInfo(Ast.Block(sets), leftSpan);
// 10. Free the temps
ag.FreeTemp(array_temp);
ag.FreeTemp(right_temp);
// 11. Return the suite statement (block)
statements[3] = Ast.Empty();
return ag.AddDebugInfo(Ast.Block(statements), totalSpan);
}
private MSAst.Expression AssignOne(AstGenerator ag) {
Debug.Assert(_left.Length == 1);
SequenceExpression seLeft = _left[0] as SequenceExpression;
SequenceExpression seRight = _right as SequenceExpression;
if (seLeft != null && seRight != null && seLeft.Items.Length == seRight.Items.Length) {
int cnt = seLeft.Items.Length;
// a, b = 1, 2, or [a,b] = 1,2 - not something like a, b = range(2)
// we can do a fast parallel assignment
MSAst.ParameterExpression[] tmps = new MSAst.ParameterExpression[cnt];
MSAst.Expression[] body = new MSAst.Expression[cnt * 2 + 1];
// generate the body, the 1st n are the temporary assigns, the
// last n are the assignments to the left hand side
// 0: tmp0 = right[0]
// ...
// n-1: tmpn-1 = right[n-1]
// n: right[0] = tmp0
// ...
// n+n-1: right[n-1] = tmpn-1
// allocate the temps first before transforming so we don't pick up a bad temp...
for (int i = 0; i < cnt; i++) {
MSAst.Expression tmpVal = ag.Transform(seRight.Items[i]);
tmps[i] = ag.GetTemporary("parallelAssign", tmpVal.Type);
body[i] = Ast.Assign(tmps[i], tmpVal);
}
// then transform which can allocate more temps
for (int i = 0; i < cnt; i++) {
body[i + cnt] = seLeft.Items[i].TransformSet(ag, SourceSpan.None, tmps[i], PythonOperationKind.None);
}
// finally free the temps.
foreach (MSAst.ParameterExpression variable in tmps) {
ag.FreeTemp(variable);
}
// 4. Create and return the resulting suite
body[cnt * 2] = AstUtils.Empty();
return ag.AddDebugInfo(Ast.Block(body), Span);
}
return _left[0].TransformSet(ag, Span, ag.Transform(_right), PythonOperationKind.None);
}
