private static bool IsElseIfOrElseClauseEquivalent(
ISyntaxFactsService syntaxFacts,
IBlockFactsService blockFacts,
IIfLikeStatementGenerator ifGenerator,
SyntaxNode elseIfOrElseClause1,
SyntaxNode elseIfOrElseClause2)
{
// Compare Else/ElseIf clauses for equality.
var isIfStatement = ifGenerator.IsIfOrElseIf(elseIfOrElseClause1);
if (isIfStatement != ifGenerator.IsIfOrElseIf(elseIfOrElseClause2))
{
// If we have one Else and one ElseIf, they're not equal.
return(false);
}
if (isIfStatement)
{
// If we have two ElseIf blocks, their conditions have to match.
var condition1 = ifGenerator.GetCondition(elseIfOrElseClause1);
var condition2 = ifGenerator.GetCondition(elseIfOrElseClause2);
if (!syntaxFacts.AreEquivalent(condition1, condition2))
{
return(false);
}
}
var statements1 = WalkDownScopeBlocks(blockFacts, blockFacts.GetStatementContainerStatements(elseIfOrElseClause1));
var statements2 = WalkDownScopeBlocks(blockFacts, blockFacts.GetStatementContainerStatements(elseIfOrElseClause2));
return(statements1.SequenceEqual(statements2, syntaxFacts.AreEquivalent));
}
private static bool ContainEquivalentStatements(
ISyntaxFactsService syntaxFacts,
IBlockFactsService blockFacts,
SyntaxNode ifStatement1,
SyntaxNode ifStatement2,
out IReadOnlyList <SyntaxNode> statements)
{
var statements1 = WalkDownScopeBlocks(blockFacts, blockFacts.GetStatementContainerStatements(ifStatement1));
var statements2 = WalkDownScopeBlocks(blockFacts, blockFacts.GetStatementContainerStatements(ifStatement2));
statements = statements1;
return(statements1.SequenceEqual(statements2, syntaxFacts.AreEquivalent));
}
private static bool IsFirstStatementOfIfOrElseIf(
IBlockFactsService blockFacts,
IIfLikeStatementGenerator ifGenerator,
SyntaxNode statement,
out SyntaxNode ifOrElseIf)
{
// Check whether the statement is a first statement inside an if or else if.
// If it's inside a block, it has to be the first statement of the block.
// We can't assume that a statement will always be in a statement container, because an if statement
// in top level code will be in a GlobalStatement.
if (blockFacts.IsStatementContainer(statement.Parent))
{
var statements = blockFacts.GetStatementContainerStatements(statement.Parent);
if (statements.Count > 0 && statements[0] == statement)
{
var rootStatements = WalkUpScopeBlocks(blockFacts, statements);
if (rootStatements.Count > 0 && ifGenerator.IsIfOrElseIf(rootStatements[0].Parent))
{
ifOrElseIf = rootStatements[0].Parent;
return(true);
}
}
}
ifOrElseIf = null;
return(false);
}
private static bool IsFirstStatementIfStatement(
IBlockFactsService blockFacts,
IIfLikeStatementGenerator ifGenerator,
SyntaxNode ifOrElseIf,
out SyntaxNode ifStatement)
{
// Check whether the first statement inside an if or else if is an if statement.
// If the if statement is inside a block, it has to be the first statement of the block.
// An if or else if should always be a statement container, but we'll do a defensive check anyway.
Debug.Assert(blockFacts.IsStatementContainer(ifOrElseIf));
if (blockFacts.IsStatementContainer(ifOrElseIf))
{
var rootStatements = blockFacts.GetStatementContainerStatements(ifOrElseIf);
var statements = WalkDownScopeBlocks(blockFacts, rootStatements);
if (statements.Count > 0 && ifGenerator.IsIfOrElseIf(statements[0]))
{
ifStatement = statements[0];
return(true);
}
}
ifStatement = null;
return(false);
}
private static async Task <bool> CanBeSeparateStatementsAsync(
Document document,
IBlockFactsService blockFacts,
IIfLikeStatementGenerator ifGenerator,
SyntaxNode ifOrElseIf,
CancellationToken cancellationToken)
{
// In order to make separate statements, ifOrElseIf must be an if statement, not an else-if clause.
if (ifGenerator.IsElseIfClause(ifOrElseIf, out _))
{
return(false);
}
// If there is an else clause, we *could* in theory separate these and move the current else clause to the second
// statement, but we won't. It would break the else-if chain in an odd way. We'll insert an else-if instead.
if (ifGenerator.GetElseIfAndElseClauses(ifOrElseIf).Length > 0)
{
return(false);
}
var insideStatements = blockFacts.GetStatementContainerStatements(ifOrElseIf);
if (insideStatements.Count == 0)
{
// Even though there are no statements inside, we still can't split this into separate statements
// because it would change the semantics from short-circuiting to always evaluating the second condition,
// breaking code like 'if (a == null || a.InstanceMethod())'.
return(false);
}
else
{
// There are statements inside. We can split this into separate statements and leave out the 'else' if
// control flow can't reach the end of these statements (otherwise, it would continue to the second 'if'
// and in the case that both conditions are true, run the same statements twice).
// This will typically look like a single return, break, continue or a throw statement.
var semanticModel = await document.GetSemanticModelAsync(cancellationToken).ConfigureAwait(false);
var controlFlow = semanticModel.AnalyzeControlFlow(insideStatements[0], insideStatements[insideStatements.Count - 1]);
return(!controlFlow.EndPointIsReachable);
}
}
private static async Task <bool> CanBeMergedAsync(
Document document,
ISyntaxFactsService syntaxFacts,
IBlockFactsService blockFacts,
IIfLikeStatementGenerator ifGenerator,
SyntaxNode outerIfOrElseIf,
SyntaxNode innerIfStatement,
CancellationToken cancellationToken)
{
// We can only merge this with the outer if statement if any inner else-if and else clauses are equal
// to else-if and else clauses following the outer if statement because we'll be removing the inner ones.
// Example of what we can merge:
// if (a)
// {
// if (b)
// Console.WriteLine();
// else
// Foo();
// }
// else
// {
// Foo();
// }
if (!System.Linq.ImmutableArrayExtensions.SequenceEqual(
ifGenerator.GetElseIfAndElseClauses(outerIfOrElseIf),
ifGenerator.GetElseIfAndElseClauses(innerIfStatement),
(a, b) => IsElseIfOrElseClauseEquivalent(syntaxFacts, blockFacts, ifGenerator, a, b)))
{
return(false);
}
var statements = blockFacts.GetStatementContainerStatements(innerIfStatement.Parent);
if (statements.Count == 1)
{
// There are no other statements below the inner if statement. Merging is OK.
return(true);
}
else
{
// There are statements below the inner if statement. We can merge if
// 1. there are equivalent statements below the outer 'if', and
// 2. control flow can't reach the end of these statements (otherwise, it would continue
// below the outer 'if' and run the same statements twice).
// This will typically look like a single return, break, continue or a throw statement.
// The opposite refactoring (SplitIntoNestedIfStatements) never generates this but we support it anyway.
// Example:
// if (a)
// {
// if (b)
// Console.WriteLine();
// return;
// }
// return;
// If we have an else-if, get the topmost if statement.
var outerIfStatement = ifGenerator.GetRootIfStatement(outerIfOrElseIf);
// A statement should always be in a statement container, but we'll do a defensive check anyway so that
// we don't crash if the helper is missing some cases or there's a new language feature it didn't account for.
Debug.Assert(blockFacts.GetStatementContainer(outerIfStatement) is object);
if (blockFacts.GetStatementContainer(outerIfStatement) is not {
} container)
{
return(false);
}
var outerStatements = blockFacts.GetStatementContainerStatements(container);
var outerIfStatementIndex = outerStatements.IndexOf(outerIfStatement);
var remainingStatements = statements.Skip(1);
var remainingOuterStatements = outerStatements.Skip(outerIfStatementIndex + 1);
if (!remainingStatements.SequenceEqual(remainingOuterStatements.Take(statements.Count - 1), syntaxFacts.AreEquivalent))
{
return(false);
}
var semanticModel = await document.GetSemanticModelAsync(cancellationToken).ConfigureAwait(false);
var controlFlow = semanticModel.AnalyzeControlFlow(statements[0], statements[statements.Count - 1]);
return(!controlFlow.EndPointIsReachable);
}
}
