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Merge pull request #5660 from weswigham/undefined-type-guards
Ignore typeof x === "undefined" type guards when narrowing
2 parents bd39847 + d7ddcc4 commit b144b5b

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lines changed

‎src/compiler/checker.ts

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@@ -200,6 +200,10 @@ namespace ts {
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"symbol": {
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type: esSymbolType,
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flags: TypeFlags.ESSymbol
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},
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"undefined": {
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type: undefinedType,
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flags: TypeFlags.ContainsUndefinedOrNull
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}
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};
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@@ -6475,6 +6479,10 @@ namespace ts {
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assumeTrue = !assumeTrue;
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}
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const typeInfo = primitiveTypeInfo[right.text];
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// Don't narrow `undefined`
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if (typeInfo && typeInfo.type === undefinedType) {
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return type;
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}
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// If the type to be narrowed is any and we're checking a primitive with assumeTrue=true, return the primitive
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if (!!(type.flags & TypeFlags.Any) && typeInfo && assumeTrue) {
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return typeInfo.type;

‎tests/baselines/reference/typeGuardTypeOfUndefined.js

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@@ -0,0 +1,357 @@
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//// [typeGuardTypeOfUndefined.ts]
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// undefined type guard adds no new type information
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function test1(a: any) {
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if (typeof a !== "undefined") {
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if (typeof a === "boolean") {
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a;
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}
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else {
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a;
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}
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}
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else {
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a;
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}
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}
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function test2(a: any) {
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if (typeof a === "undefined") {
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if (typeof a === "boolean") {
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a;
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}
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else {
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a;
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}
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}
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else {
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a;
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}
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}
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function test3(a: any) {
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if (typeof a === "undefined" || typeof a === "boolean") {
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a;
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}
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else {
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a;
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}
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}
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function test4(a: any) {
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if (typeof a !== "undefined" && typeof a === "boolean") {
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a;
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}
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else {
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a;
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}
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}
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function test5(a: boolean | void) {
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if (typeof a !== "undefined") {
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if (typeof a === "boolean") {
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a;
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}
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else {
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a;
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}
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}
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else {
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a;
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}
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}
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function test6(a: boolean | void) {
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if (typeof a === "undefined") {
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if (typeof a === "boolean") {
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a;
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}
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else {
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a;
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}
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}
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else {
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a;
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}
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}
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function test7(a: boolean | void) {
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if (typeof a === "undefined" || typeof a === "boolean") {
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a;
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}
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else {
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a;
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}
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}
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function test8(a: boolean | void) {
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if (typeof a !== "undefined" && typeof a === "boolean") {
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a;
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}
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else {
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a;
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}
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}
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function test9(a: boolean | number) {
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if (typeof a !== "undefined") {
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if (typeof a === "boolean") {
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a;
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}
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else {
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a;
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}
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}
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else {
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a;
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}
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}
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function test10(a: boolean | number) {
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if (typeof a === "undefined") {
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if (typeof a === "boolean") {
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a;
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}
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else {
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a;
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}
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}
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else {
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a;
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}
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}
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function test11(a: boolean | number) {
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if (typeof a === "undefined" || typeof a === "boolean") {
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a;
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}
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else {
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a;
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}
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}
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function test12(a: boolean | number) {
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if (typeof a !== "undefined" && typeof a === "boolean") {
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a;
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}
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else {
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a;
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}
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}
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function test13(a: boolean | number | void) {
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if (typeof a !== "undefined") {
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if (typeof a === "boolean") {
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a;
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}
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else {
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a;
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}
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}
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else {
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a;
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}
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}
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function test14(a: boolean | number | void) {
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if (typeof a === "undefined") {
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if (typeof a === "boolean") {
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a;
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}
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else {
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a;
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}
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}
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else {
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a;
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}
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}
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function test15(a: boolean | number | void) {
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if (typeof a === "undefined" || typeof a === "boolean") {
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a;
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}
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else {
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a;
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}
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}
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function test16(a: boolean | number | void) {
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if (typeof a !== "undefined" && typeof a === "boolean") {
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a;
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}
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else {
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a;
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}
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}
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//// [typeGuardTypeOfUndefined.js]
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// undefined type guard adds no new type information
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function test1(a) {
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if (typeof a !== "undefined") {
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if (typeof a === "boolean") {
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a;
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}
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else {
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a;
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}
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}
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else {
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a;
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}
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}
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function test2(a) {
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if (typeof a === "undefined") {
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if (typeof a === "boolean") {
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a;
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}
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else {
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a;
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}
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}
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else {
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a;
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}
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}
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function test3(a) {
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if (typeof a === "undefined" || typeof a === "boolean") {
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a;
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}
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else {
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a;
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}
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}
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function test4(a) {
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if (typeof a !== "undefined" && typeof a === "boolean") {
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a;
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}
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else {
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a;
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}
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}
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function test5(a) {
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if (typeof a !== "undefined") {
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if (typeof a === "boolean") {
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a;
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}
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else {
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a;
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}
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}
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else {
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a;
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}
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}
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function test6(a) {
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if (typeof a === "undefined") {
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if (typeof a === "boolean") {
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a;
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}
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else {
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a;
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}
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}
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else {
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a;
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}
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}
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function test7(a) {
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if (typeof a === "undefined" || typeof a === "boolean") {
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a;
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}
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else {
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a;
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}
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}
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function test8(a) {
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if (typeof a !== "undefined" && typeof a === "boolean") {
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a;
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}
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else {
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a;
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}
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}
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function test9(a) {
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if (typeof a !== "undefined") {
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if (typeof a === "boolean") {
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a;
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}
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else {
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a;
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}
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}
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else {
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a;
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}
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}
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function test10(a) {
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if (typeof a === "undefined") {
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if (typeof a === "boolean") {
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a;
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}
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else {
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a;
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}
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}
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else {
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a;
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}
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}
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function test11(a) {
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if (typeof a === "undefined" || typeof a === "boolean") {
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a;
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}
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else {
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a;
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}
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}
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function test12(a) {
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if (typeof a !== "undefined" && typeof a === "boolean") {
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a;
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}
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else {
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a;
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}
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}
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function test13(a) {
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if (typeof a !== "undefined") {
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if (typeof a === "boolean") {
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a;
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}
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else {
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a;
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}
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}
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else {
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a;
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}
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}
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function test14(a) {
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if (typeof a === "undefined") {
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if (typeof a === "boolean") {
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a;
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}
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else {
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a;
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}
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}
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else {
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a;
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}
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}
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function test15(a) {
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if (typeof a === "undefined" || typeof a === "boolean") {
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a;
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}
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else {
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a;
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}
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}
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function test16(a) {
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if (typeof a !== "undefined" && typeof a === "boolean") {
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a;
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}
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else {
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a;
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}
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}

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