Function compareSignaturesRelated

test/fixtures/snapshot/typescript.js:64342–64458

* See signatureRelatedTo, compareSignaturesIdentical

(source, target, checkMode, reportErrors, errorReporter, incompatibleErrorReporter, compareTypes, reportUnreliableMarkers)

         * See signatureRelatedTo, compareSignaturesIdentical
         */
        function compareSignaturesRelated(source, target, checkMode, reportErrors, errorReporter, incompatibleErrorReporter, compareTypes, reportUnreliableMarkers) {
            // TODO (drosen): De-duplicate code between related functions.
            if (source === target) {
                return -1 /* Ternary.True */;
            }
            if (isAnySignature(target)) {
                return -1 /* Ternary.True */;
            }
            var targetCount = getParameterCount(target);
            var sourceHasMoreParameters = !hasEffectiveRestParameter(target) &&
                (checkMode & 8 /* SignatureCheckMode.StrictArity */ ? hasEffectiveRestParameter(source) || getParameterCount(source) > targetCount : getMinArgumentCount(source) > targetCount);
            if (sourceHasMoreParameters) {
                return 0 /* Ternary.False */;
            }
            if (source.typeParameters && source.typeParameters !== target.typeParameters) {
                target = getCanonicalSignature(target);
                source = instantiateSignatureInContextOf(source, target, /*inferenceContext*/ undefined, compareTypes);
            }
            var sourceCount = getParameterCount(source);
            var sourceRestType = getNonArrayRestType(source);
            var targetRestType = getNonArrayRestType(target);
            if (sourceRestType || targetRestType) {
                void instantiateType(sourceRestType || targetRestType, reportUnreliableMarkers);
            }
            var kind = target.declaration ? target.declaration.kind : 0 /* SyntaxKind.Unknown */;
            var strictVariance = !(checkMode & 3 /* SignatureCheckMode.Callback */) && strictFunctionTypes && kind !== 169 /* SyntaxKind.MethodDeclaration */ &&
                kind !== 168 /* SyntaxKind.MethodSignature */ && kind !== 171 /* SyntaxKind.Constructor */;
            var result = -1 /* Ternary.True */;
            var sourceThisType = getThisTypeOfSignature(source);
            if (sourceThisType && sourceThisType !== voidType) {
                var targetThisType = getThisTypeOfSignature(target);
                if (targetThisType) {
                    // void sources are assignable to anything.
                    var related = !strictVariance && compareTypes(sourceThisType, targetThisType, /*reportErrors*/ false)
                        || compareTypes(targetThisType, sourceThisType, reportErrors);
                    if (!related) {
                        if (reportErrors) {
                            errorReporter(ts.Diagnostics.The_this_types_of_each_signature_are_incompatible);
                        }
                        return 0 /* Ternary.False */;
                    }
                    result &= related;
                }
            }
            var paramCount = sourceRestType || targetRestType ? Math.min(sourceCount, targetCount) : Math.max(sourceCount, targetCount);
            var restIndex = sourceRestType || targetRestType ? paramCount - 1 : -1;
            for (var i = 0; i < paramCount; i++) {
                var sourceType = i === restIndex ? getRestTypeAtPosition(source, i) : tryGetTypeAtPosition(source, i);
                var targetType = i === restIndex ? getRestTypeAtPosition(target, i) : tryGetTypeAtPosition(target, i);
                if (sourceType && targetType) {
                    // In order to ensure that any generic type Foo<T> is at least co-variant with respect to T no matter
                    // how Foo uses T, we need to relate parameters bi-variantly (given that parameters are input positions,
                    // they naturally relate only contra-variantly). However, if the source and target parameters both have
                    // function types with a single call signature, we know we are relating two callback parameters. In
                    // that case it is sufficient to only relate the parameters of the signatures co-variantly because,
                    // similar to return values, callback parameters are output positions. This means that a Promise<T>,
                    // where T is used only in callback parameter positions, will be co-variant (as opposed to bi-variant)
                    // with respect to T.