demo/typescript.js
function resolveDecorator(node, candidatesOutArray) {
            var funcType = checkExpression(node.expression);
            var apparentType = getApparentType(funcType);
            if (apparentType === unknownType) {
                return resolveErrorCall(node);
            }
            var callSignatures = getSignaturesOfType(apparentType, 0 /* Call */);
            if (funcType === anyType || (!callSignatures.length && !(funcType.flags & 16384 /* Union */) && isTypeAssignableTo(funcType, globalFunctionType))) {
                return resolveUntypedCall(node);
            }
            var headMessage = getDiagnosticHeadMessageForDecoratorResolution(node);
            if (!callSignatures.length) {
                var errorInfo;
                errorInfo = ts.chainDiagnosticMessages(errorInfo, ts.Diagnostics.Cannot_invoke_an_expression_whose_type_lacks_a_call_signature);
                errorInfo = ts.chainDiagnosticMessages(errorInfo, headMessage);
                diagnostics.add(ts.createDiagnosticForNodeFromMessageChain(node, errorInfo));
                return resolveErrorCall(node);
            }
            return resolveCall(node, callSignatures, candidatesOutArray, headMessage);
        }
function resolveDecorator(node, candidatesOutArray) {
            var funcType = checkExpression(node.expression);
            var apparentType = getApparentType(funcType);
            if (apparentType === unknownType) {
                return resolveErrorCall(node);
            }
            var callSignatures = getSignaturesOfType(apparentType, 0 /* Call */);
            if (funcType === anyType || (!callSignatures.length && !(funcType.flags & 16384 /* Union */) && isTypeAssignableTo(funcType, globalFunctionType))) {
                return resolveUntypedCall(node);
            }
            var headMessage = getDiagnosticHeadMessageForDecoratorResolution(node);
            if (!callSignatures.length) {
                var errorInfo;
                errorInfo = ts.chainDiagnosticMessages(errorInfo, ts.Diagnostics.Cannot_invoke_an_expression_whose_type_lacks_a_call_signature);
                errorInfo = ts.chainDiagnosticMessages(errorInfo, headMessage);
                diagnostics.add(ts.createDiagnosticForNodeFromMessageChain(node, errorInfo));
                return resolveErrorCall(node);
            }
            return resolveCall(node, callSignatures, candidatesOutArray, headMessage);
        }
Resolves a decorator as if it were a call expression.