ILSpy/ICSharpCode.Decompiler/CSharp/Transforms/IntroduceUsingDeclarations.cs

// Copyright (c) 2011 AlphaSierraPapa for the SharpDevelop Team
// 
// Permission is hereby granted, free of charge, to any person obtaining a copy of this
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// to whom the Software is furnished to do so, subject to the following conditions:
// 
// The above copyright notice and this permission notice shall be included in all copies or
// substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
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using System;
using System.Collections.Generic;
using System.Linq;
using ICSharpCode.Decompiler.CSharp.Resolver;
using ICSharpCode.Decompiler.CSharp.Syntax;
using ICSharpCode.Decompiler.CSharp.TypeSystem;
using ICSharpCode.Decompiler.Semantics;
using ICSharpCode.Decompiler.TypeSystem;

namespace ICSharpCode.Decompiler.CSharp.Transforms
{
	/// <summary>
	/// Introduces using declarations.
	/// </summary>
	public class IntroduceUsingDeclarations : IAstTransform
	{
		public bool FullyQualifyAmbiguousTypeNames = true;
		
		public void Run(AstNode compilationUnit, TransformContext context)
		{
			// First determine all the namespaces that need to be imported:
			var requiredImports = new FindRequiredImports(context);
			compilationUnit.AcceptVisitor(requiredImports);
			
			requiredImports.ImportedNamespaces.Add("System"); // always import System, even when not necessary
			
			var usingScope = new UsingScope();

			var insertionPoint = compilationUnit.Children.LastOrDefault(n => n is PreProcessorDirective p && p.Type == PreProcessorDirectiveType.Define);
			
			// Now add using declarations for those namespaces:
			foreach (string ns in requiredImports.ImportedNamespaces.OrderByDescending(n => n)) {
				// we go backwards (OrderByDescending) through the list of namespaces because we insert them backwards
				// (always inserting at the start of the list)
				string[] parts = ns.Split('.');
				AstType nsType = new SimpleType(parts[0]);
				for (int i = 1; i < parts.Length; i++) {
					nsType = new MemberType { Target = nsType, MemberName = parts[i] };
				}
				if (FullyQualifyAmbiguousTypeNames) {
					var reference = nsType.ToTypeReference(NameLookupMode.TypeInUsingDeclaration) as TypeOrNamespaceReference;
					if (reference != null)
						usingScope.Usings.Add(reference);
				}
				compilationUnit.InsertChildAfter(insertionPoint, new UsingDeclaration { Import = nsType }, SyntaxTree.MemberRole);
			}
			
			if (!FullyQualifyAmbiguousTypeNames)
				return;

			// verify that the SimpleTypes refer to the correct type (no ambiguities)
			compilationUnit.AcceptVisitor(new FullyQualifyAmbiguousTypeNamesVisitor(context, usingScope));
		}
		
		sealed class FindRequiredImports : DepthFirstAstVisitor
		{
			string currentNamespace;

			public readonly HashSet<string> DeclaredNamespaces = new HashSet<string>() { string.Empty };
			public readonly HashSet<string> ImportedNamespaces = new HashSet<string>();
			
			public FindRequiredImports(TransformContext context)
			{
				this.currentNamespace = context.DecompiledTypeDefinition != null ? context.DecompiledTypeDefinition.Namespace : string.Empty;
			}
			
			bool IsParentOfCurrentNamespace(string ns)
			{
				if (ns.Length == 0)
					return true;
				if (currentNamespace.StartsWith(ns, StringComparison.Ordinal)) {
					if (currentNamespace.Length == ns.Length)
						return true;
					if (currentNamespace[ns.Length] == '.')
						return true;
				}
				return false;
			}
			
			public override void VisitSimpleType(SimpleType simpleType)
			{
				var trr = simpleType.Annotation<TypeResolveResult>();
				if (trr != null && !IsParentOfCurrentNamespace(trr.Type.Namespace)) {
					ImportedNamespaces.Add(trr.Type.Namespace);
				}
				base.VisitSimpleType(simpleType); // also visit type arguments
			}
			
			public override void VisitNamespaceDeclaration(NamespaceDeclaration namespaceDeclaration)
			{
				string oldNamespace = currentNamespace;
				foreach (string ident in namespaceDeclaration.Identifiers) {
					currentNamespace = NamespaceDeclaration.BuildQualifiedName(currentNamespace, ident);
					DeclaredNamespaces.Add(currentNamespace);
				}
				base.VisitNamespaceDeclaration(namespaceDeclaration);
				currentNamespace = oldNamespace;
			}
		}
		
		sealed class FullyQualifyAmbiguousTypeNamesVisitor : DepthFirstAstVisitor
		{
			Stack<CSharpTypeResolveContext> context;
			TypeSystemAstBuilder astBuilder;
			
			public FullyQualifyAmbiguousTypeNamesVisitor(TransformContext context, UsingScope usingScope)
			{
				this.context = new Stack<CSharpTypeResolveContext>();
				var currentContext = new CSharpTypeResolveContext(context.TypeSystem.MainAssembly, usingScope.Resolve(context.TypeSystem.Compilation));
				this.context.Push(currentContext);
				this.astBuilder = CreateAstBuilder(currentContext);
			}

			static TypeSystemAstBuilder CreateAstBuilder(CSharpTypeResolveContext context)
			{
				return new TypeSystemAstBuilder(new CSharpResolver(context)) {
					AddResolveResultAnnotations = true,
					UseAliases = true
				};
			}
			
			public override void VisitNamespaceDeclaration(NamespaceDeclaration namespaceDeclaration)
			{
				var previousContext = context.Peek();
				var usingScope = previousContext.CurrentUsingScope.UnresolvedUsingScope;
				foreach (string ident in namespaceDeclaration.Identifiers) {
					usingScope = new UsingScope(usingScope, ident);
				}
				var currentContext = new CSharpTypeResolveContext(previousContext.CurrentAssembly, usingScope.Resolve(previousContext.Compilation));
				context.Push(currentContext);
				try {
					astBuilder = CreateAstBuilder(currentContext);
					base.VisitNamespaceDeclaration(namespaceDeclaration);
				} finally {
					context.Pop();
				}
			}
			
			public override void VisitTypeDeclaration(TypeDeclaration typeDeclaration)
			{
				var currentContext = context.Peek().WithCurrentTypeDefinition(typeDeclaration.GetSymbol() as ITypeDefinition);
				context.Push(currentContext);
				try {
					astBuilder = CreateAstBuilder(currentContext);
					base.VisitTypeDeclaration(typeDeclaration);
				} finally {
					context.Pop();
				}
			}
			
			public override void VisitSimpleType(SimpleType simpleType)
			{
				TypeResolveResult rr;
				if ((rr = simpleType.Annotation<TypeResolveResult>()) == null) {
					base.VisitSimpleType(simpleType);
					return;
				}
				// HACK : ignore type names in attributes (TypeSystemAstBuilder doesn't handle them correctly)
				if (simpleType.Parent is Syntax.Attribute) {
					base.VisitSimpleType(simpleType);
					return;
				}
				astBuilder.NameLookupMode = simpleType.GetNameLookupMode();
				if (astBuilder.NameLookupMode == NameLookupMode.Type) {
					AstType outermostType = simpleType;
					while (outermostType.Parent is AstType)
						outermostType = (AstType)outermostType.Parent;
					if (outermostType.Parent is TypeReferenceExpression) {
						// ILSpy uses TypeReferenceExpression in expression context even when the C# parser
						// wouldn't know that it's a type reference.
						// Fall back to expression-mode lookup in these cases:
						astBuilder.NameLookupMode = NameLookupMode.Expression;
					}
				}
				simpleType.ReplaceWith(astBuilder.ConvertType(rr.Type));
			}
		}
	}
}