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);
}
}
}
/// <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>
internal override MSAst.Expression Transform(AstGenerator ag) {
MSAst.ParameterExpression lineUpdated = ag.GetTemporary("$lineUpdated_with", typeof(bool));
// Five statements in the result...
MSAst.Expression[] statements = new MSAst.Expression[6];
//******************************************************************
// 1. mgr = (EXPR)
//******************************************************************
MSAst.ParameterExpression manager = ag.GetTemporary("with_manager");
statements[0] = ag.MakeAssignment(
manager,
ag.Transform(_contextManager),
new SourceSpan(Start, _header)
);
//******************************************************************
// 2. exit = mgr.__exit__ # Not calling it yet
//******************************************************************
MSAst.ParameterExpression exit = ag.GetTemporary("with_exit");
statements[1] = ag.MakeAssignment(
exit,
ag.Get(
typeof(object),
"__exit__",
manager
)
);
//******************************************************************
// 3. value = mgr.__enter__()
//******************************************************************
MSAst.ParameterExpression value = ag.GetTemporary("with_value");
statements[2] = ag.AddDebugInfo(
ag.MakeAssignment(
value,
ag.Invoke(
typeof(object),
new CallSignature(0),
ag.Get(
typeof(object),
"__enter__",
manager
)
)
),
new SourceSpan(Start, _header)
);
//******************************************************************
// 4. exc = True
//******************************************************************
MSAst.ParameterExpression exc = ag.GetTemporary("with_exc", typeof(bool));
statements[3] = ag.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 = ag.GetTemporary("exception", typeof(Exception));
MSAst.ParameterExpression nestedFrames = ag.GetTemporary("$nestedFrames", typeof(List<DynamicStackFrame>));
statements[4] =
// try:
AstUtils.Try(
AstUtils.Try(// try statement body
ag.PushLineUpdated(false, lineUpdated),
_var != null ?
ag.AddDebugInfo(
Ast.Block(
// VAR = value
_var.TransformSet(ag, SourceSpan.None, value, PythonOperationKind.None),
// BLOCK
ag.Transform(_body),
AstUtils.Empty()
),
_body.Span
) :
// BLOCK
ag.Transform(_body) // except:, // try statement location
).Catch(exception,
// Python specific exception handling code
TryStatement.GetTracebackHeader(
ag,
exception,
ag.AddDebugInfo(
Ast.Block(
// exc = False
ag.MakeAssignment(
exc,
AstUtils.Constant(false)
),
Ast.Assign(
nestedFrames,
Ast.Call(AstGenerator.GetHelperMethod("GetAndClearDynamicStackFrames"))
),
// if not exit(*sys.exc_info()):
// raise
AstUtils.IfThen(
ag.Convert(
typeof(bool),
ConversionResultKind.ExplicitCast,
ag.Operation(
typeof(bool),
PythonOperationKind.Not,
MakeExitCall(ag, exit, exception)
)
),
ag.UpdateLineUpdated(true),
Ast.Call(
AstGenerator.GetHelperMethod("SetDynamicStackFrames"),
nestedFrames
),
Ast.Rethrow()
)
),
_body.Span
)
),
Ast.Call(
AstGenerator.GetHelperMethod("SetDynamicStackFrames"),
nestedFrames
),
ag.PopLineUpdated(lineUpdated),
Ast.Empty()
)
// finally:
).Finally(
// if exc:
// exit(None, None, None)
AstUtils.IfThen(
exc,
ag.AddDebugInfo(
Ast.Block(
Ast.Dynamic(
ag.BinderState.Invoke(
new CallSignature(3) // signature doesn't include function
),
typeof(object),
new MSAst.Expression[] {
ag.LocalContext,
exit,
AstUtils.Constant(null),
AstUtils.Constant(null),
AstUtils.Constant(null)
}
),
Ast.Empty()
),
_contextManager.Span
)
)
);
statements[4] = ag.AddDebugInfo(statements[4], Span);
statements[5] = AstUtils.Empty();
return ag.AddDebugInfo(Ast.Block(statements), _body.Span);
}
