private static Package CheckSemantics(PackageSyntax packageSyntax)
{
DeclarationNumberAssigner.AssignIn(packageSyntax.AllEntityDeclarations);
// Resolve symbols for the entities
EntitySymbolBuilder.BuildFor(packageSyntax);
var stringSymbol = packageSyntax.SymbolTrees
.GlobalSymbols
.OfType <ObjectTypeSymbol>()
.SingleOrDefault(s => s.Name == "String");
// Basic Analysis includes: Name Binding, Type Checking, Constant Folding
BasicAnalyzer.Check(packageSyntax, stringSymbol);
// If there are errors from the basic analysis phase, don't continue on
packageSyntax.Diagnostics.ThrowIfFatalErrors();
#if DEBUG
new SymbolValidator(packageSyntax.SymbolTree).Validate(packageSyntax.AllEntityDeclarations);
new TypeFulfillmentValidator().Validate(packageSyntax.AllEntityDeclarations);
new TypeKnownValidator().Validate(packageSyntax.AllEntityDeclarations);
new ExpressionSemanticsValidator().Validate(packageSyntax.AllEntityDeclarations);
#endif
var package = new ASTBuilder().BuildPackage(packageSyntax);
// From this point forward, analysis focuses on executable declarations (i.e. invocables and field initializers)
var executableDeclarations = package.AllDeclarations.OfType <IExecutableDeclaration>().ToFixedSet();
ShadowChecker.Check(executableDeclarations, package.Diagnostics);
DataFlowAnalysis.Check(DefiniteAssignmentAnalyzer.Instance, executableDeclarations, package.SymbolTree, package.Diagnostics);
DataFlowAnalysis.Check(BindingMutabilityAnalyzer.Instance, executableDeclarations, package.SymbolTree, package.Diagnostics);
DataFlowAnalysis.Check(UseOfMovedValueAnalyzer.Instance, executableDeclarations, package.SymbolTree, package.Diagnostics);
// TODO use DataFlowAnalysis to check for unused variables and report use of variables starting with `_`
// Compute variable liveness needed by reachability analyzer
DataFlowAnalysis.Check(LivenessAnalyzer.Instance, executableDeclarations, package.SymbolTree, package.Diagnostics);
ReachabilityAnalyzer.Analyze(executableDeclarations, package.SymbolTree, package.Diagnostics);
// TODO remove live variables if SaveLivenessAnalysis is false
return(package);
}