C# BlockContext.StartFlowBranching方法代码示例

		/// <summary>
		///   We already know that the statement is unreachable, but we still
		///   need to resolve it to catch errors.
		/// </summary>
		public virtual bool ResolveUnreachable (BlockContext ec, bool warn)
		{
			//
			// This conflicts with csc's way of doing this, but IMHO it's
			// the right thing to do.
			//
			// If something is unreachable, we still check whether it's
			// correct.  This means that you cannot use unassigned variables
			// in unreachable code, for instance.
			//

			if (warn)
				ec.Report.Warning (162, 2, loc, "Unreachable code detected");

			ec.StartFlowBranching (FlowBranching.BranchingType.Block, loc);
			bool ok = Resolve (ec);
			ec.KillFlowBranching ();

			return ok;
		}

		public override bool Resolve (BlockContext ec)
		{
			bool ok = true;

			ec.StartFlowBranching (FlowBranching.BranchingType.Loop, loc);

			bool was_unreachable = ec.CurrentBranching.CurrentUsageVector.IsUnreachable;

			ec.StartFlowBranching (FlowBranching.BranchingType.Embedded, loc);
			if (!EmbeddedStatement.Resolve (ec))
				ok = false;
			ec.EndFlowBranching ();

			if (ec.CurrentBranching.CurrentUsageVector.IsUnreachable && !was_unreachable)
				ec.Report.Warning (162, 2, expr.Location, "Unreachable code detected");

			expr = expr.Resolve (ec);
			if (expr == null)
				ok = false;
			else if (expr is Constant){
				bool infinite = !((Constant) expr).IsDefaultValue;
				if (infinite)
					ec.CurrentBranching.CurrentUsageVector.Goto ();
			}

			ec.EndFlowBranching ();

			return ok;
		}

		public override bool Resolve (BlockContext ec)
		{
			Block prev_block = ec.CurrentBlock;
			bool ok = true;

			int errors = ec.Report.Errors;

			ec.CurrentBlock = this;
			ec.StartFlowBranching (this);

			Report.Debug (4, "RESOLVE BLOCK", StartLocation, ec.CurrentBranching);

			//
			// Compiler generated scope statements
			//
			if (scope_initializers != null) {
				foreach (Statement s in scope_initializers)
					s.Resolve (ec);
			}

			//
			// This flag is used to notate nested statements as unreachable from the beginning of this block.
			// For the purposes of this resolution, it doesn't matter that the whole block is unreachable 
			// from the beginning of the function.  The outer Resolve() that detected the unreachability is
			// responsible for handling the situation.
			//
			int statement_count = statements.Count;
			for (int ix = 0; ix < statement_count; ix++){
				Statement s = (Statement) statements [ix];
				if (s == null)
					continue; 
				
				// Check possible empty statement (CS0642)
				if (ix + 1 < statement_count && ec.Report.WarningLevel >= 3 &&
					statements [ix + 1] is ExplicitBlock)
					CheckPossibleMistakenEmptyStatement (ec, s);

				//
				// Warn if we detect unreachable code.
				//
				if (unreachable) {
					if (s is EmptyStatement)
						continue;

					if (!unreachable_shown && !(s is LabeledStatement)) {
						ec.Report.Warning (162, 2, s.loc, "Unreachable code detected");
						unreachable_shown = true;
					}

					Block c_block = s as Block;
					if (c_block != null)
						c_block.unreachable = c_block.unreachable_shown = true;
				}

				//
				// Note that we're not using ResolveUnreachable() for unreachable
				// statements here.  ResolveUnreachable() creates a temporary
				// flow branching and kills it afterwards.  This leads to problems
				// if you have two unreachable statements where the first one
				// assigns a variable and the second one tries to access it.
				//

				if (!s.Resolve (ec)) {
					ok = false;
					if (ec.IsInProbingMode)
						break;

					statements [ix] = EmptyStatement.Value;
					continue;
				}

				if (unreachable && !(s is LabeledStatement) && !(s is Block))
					statements [ix] = EmptyStatement.Value;

				unreachable = ec.CurrentBranching.CurrentUsageVector.IsUnreachable;
				if (unreachable && s is LabeledStatement)
					throw new InternalErrorException ("should not happen");
			}

			Report.Debug (4, "RESOLVE BLOCK DONE", StartLocation,
				      ec.CurrentBranching, statement_count);

			while (ec.CurrentBranching is FlowBranchingLabeled)
				ec.EndFlowBranching ();

			bool flow_unreachable = ec.EndFlowBranching ();

			ec.CurrentBlock = prev_block;

			if (flow_unreachable)
				flags |= Flags.HasRet;

			// If we're a non-static `struct' constructor which doesn't have an
			// initializer, then we must initialize all of the struct's fields.
			if (this == Toplevel && !Toplevel.IsThisAssigned (ec) && !flow_unreachable)
				ok = false;

			if ((labels != null) && (ec.Report.WarningLevel >= 2)) {
				foreach (LabeledStatement label in labels.Values)
					if (!label.HasBeenReferenced)
//.........这里部分代码省略.........

		public override bool Resolve (BlockContext ec)
		{
			VariableReference vr;
			bool vr_locked = false;

			using (ec.Set (ResolveContext.Options.UsingInitializerScope)) {
				if (decl.Variable == null) {
					vr = decl.ResolveExpression (ec) as VariableReference;
					if (vr != null) {
						vr_locked = vr.IsLockedByStatement;
						vr.IsLockedByStatement = true;
					}
				} else {
					if (!decl.Resolve (ec))
						return false;

					if (decl.Declarators != null) {
						stmt = decl.RewriteForDeclarators (ec, stmt);
					}

					vr = null;
				}
			}

			ec.StartFlowBranching (this);

			stmt.Resolve (ec);

			ec.EndFlowBranching ();

			if (vr != null)
				vr.IsLockedByStatement = vr_locked;

			base.Resolve (ec);

			return true;
		}

//.........这里部分代码省略.........
				// but the production on the grammar is more concise.
				//
				// So we have to enforce these rules here.
				//
				// We do not resolve before doing the case 1 test,
				// because the grammar is explicit in that the token &
				// is present, so we need to test for this particular case.
				//

				if (e is Cast){
					ec.Report.Error (254, loc, "The right hand side of a fixed statement assignment may not be a cast expression");
					return false;
				}

				using (ec.Set (ResolveContext.Options.FixedInitializerScope)) {
					e = e.Resolve (ec);
				}

				if (e == null)
					return false;

				//
				// Case 2: Array
				//
				if (e.Type.IsArray){
					TypeSpec array_type = TypeManager.GetElementType (e.Type);
					
					//
					// Provided that array_type is unmanaged,
					//
					if (!TypeManager.VerifyUnmanaged (ec.Compiler, array_type, loc))
						return false;

					//
					// and T* is implicitly convertible to the
					// pointer type given in the fixed statement.
					//
					ArrayPtr array_ptr = new ArrayPtr (e, array_type, loc);
					
					Expression converted = Convert.ImplicitConversionRequired (
						ec, array_ptr, vi.VariableType, loc);
					if (converted == null)
						return false;
					
					//
					// fixed (T* e_ptr = (e == null || e.Length == 0) ? null : converted [0])
					//
					converted = new Conditional (new BooleanExpression (new Binary (Binary.Operator.LogicalOr,
						new Binary (Binary.Operator.Equality, e, new NullLiteral (loc), loc),
						new Binary (Binary.Operator.Equality, new MemberAccess (e, "Length"), new IntConstant (0, loc), loc), loc)),
							new NullPointer (loc),
							converted, loc);

					converted = converted.Resolve (ec);					

					data [i] = new ExpressionEmitter (converted, vi);
					i++;

					continue;
				}

				//
				// Case 3: string
				//
				if (e.Type == TypeManager.string_type){
					data [i] = new StringEmitter (e, vi, loc).Resolve (ec);
					i++;
					continue;
				}

				// Case 4: fixed buffer
				if (e is FixedBufferPtr) {
					data [i++] = new ExpressionEmitter (e, vi);
					continue;
				}

				//
				// Case 1: & object.
				//
				Unary u = e as Unary;
				if (u != null && u.Oper == Unary.Operator.AddressOf) {
					IVariableReference vr = u.Expr as IVariableReference;
					if (vr == null || !vr.IsFixed) {
						data [i] = new ExpressionEmitter (e, vi);
					}
				}

				if (data [i++] == null)
					ec.Report.Error (213, vi.Location, "You cannot use the fixed statement to take the address of an already fixed expression");

				e = Convert.ImplicitConversionRequired (ec, e, expr_type, loc);
			}

			ec.StartFlowBranching (FlowBranching.BranchingType.Conditional, loc);
			bool ok = statement.Resolve (ec);
			bool flow_unreachable = ec.EndFlowBranching ();
			has_ret = flow_unreachable;

			return ok;
		}

		protected override Expression DoResolve (ResolveContext ec)
		{
			IteratorHost = (IteratorStorey) block.TopBlock.AnonymousMethodStorey;

			BlockContext ctx = new BlockContext (ec, block, ReturnType);
			ctx.CurrentAnonymousMethod = this;

			ctx.StartFlowBranching (this, ec.CurrentBranching);
			Block.Resolve (ctx);
			ctx.EndFlowBranching ();

			var move_next = new IteratorMethod (IteratorHost, new TypeExpression (TypeManager.bool_type, loc),
				Modifiers.PUBLIC, new MemberName ("MoveNext", Location));
			move_next.Block.AddStatement (new MoveNextMethodStatement (this));
			IteratorHost.AddMethod (move_next);

			eclass = ExprClass.Value;
			return this;
		}

 public override bool Resolve(BlockContext ec)
 {
     ec.StartFlowBranching (iterator);
     bool ok = original_block.Resolve (ec);
     ec.EndFlowBranching ();
     return ok;
 }