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AndaristRyanCavanaugh
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RyanCavanaugh
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Fixed an issue causing spurious "used before being assigned" errors in for of/in loops (#61376)
Co-authored-by: Ryan Cavanaugh <RyanCavanaugh@users.noreply.github.com>
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‎src/compiler/checker.ts‎

Lines changed: 1 addition & 1 deletion
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@@ -31113,7 +31113,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
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// We only look for uninitialized variables in strict null checking mode, and only when we can analyze
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// the entire control flow graph from the variable's declaration (i.e. when the flow container and
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// declaration container are the same).
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const isNeverInitialized = immediateDeclaration && isVariableDeclaration(immediateDeclaration) && !immediateDeclaration.initializer && !immediateDeclaration.exclamationToken && isMutableLocalVariableDeclaration(immediateDeclaration) && !isSymbolAssignedDefinitely(symbol);
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const isNeverInitialized = immediateDeclaration && isVariableDeclaration(immediateDeclaration) && !isForInOrOfStatement(immediateDeclaration.parent.parent) && !immediateDeclaration.initializer && !immediateDeclaration.exclamationToken && isMutableLocalVariableDeclaration(immediateDeclaration) && !isSymbolAssignedDefinitely(symbol);
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const assumeInitialized = isParameter || isAlias ||
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(isOuterVariable && !isNeverInitialized) ||
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isSpreadDestructuringAssignmentTarget || isModuleExports || isSameScopedBindingElement(node, declaration) ||

‎tests/baselines/reference/unusedLocalsInForInOrOf1.errors.txt‎

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unusedLocalsInForInOrOf1.ts(2,12): error TS6133: 'f' is declared but its value is never read.
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unusedLocalsInForInOrOf1.ts(8,7): error TS6133: 'f' is declared but its value is never read.
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unusedLocalsInForInOrOf1.ts(14,12): error TS6133: 'g' is declared but its value is never read.
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unusedLocalsInForInOrOf1.ts(20,12): error TS6133: 'f2' is declared but its value is never read.
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unusedLocalsInForInOrOf1.ts(26,7): error TS6133: 'f2' is declared but its value is never read.
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unusedLocalsInForInOrOf1.ts(32,12): error TS6133: 'g2' is declared but its value is never read.
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unusedLocalsInForInOrOf1.ts(38,12): error TS6133: 'f3' is declared but its value is never read.
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unusedLocalsInForInOrOf1.ts(44,7): error TS6133: 'f3' is declared but its value is never read.
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unusedLocalsInForInOrOf1.ts(50,12): error TS6133: 'g3' is declared but its value is never read.
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==== unusedLocalsInForInOrOf1.ts (9 errors) ====
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for (let x of [1, 2]) {
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function f() {
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~
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!!! error TS6133: 'f' is declared but its value is never read.
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x;
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}
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}
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for (let x of [1, 2]) {
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let f = () => {
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~
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!!! error TS6133: 'f' is declared but its value is never read.
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x;
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};
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}
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for (const x of [1, 2]) {
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function g() {
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~
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!!! error TS6133: 'g' is declared but its value is never read.
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x;
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}
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}
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for (let x in { a: 1, b: 2 }) {
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function f2() {
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~~
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!!! error TS6133: 'f2' is declared but its value is never read.
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x;
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}
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}
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for (let x in { a: 1, b: 2 }) {
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let f2 = () => {
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~~
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!!! error TS6133: 'f2' is declared but its value is never read.
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x;
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};
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}
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for (const x in { a: 1, b: 2 }) {
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function g2() {
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~~
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!!! error TS6133: 'g2' is declared but its value is never read.
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x;
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}
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}
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for (let { x } of [{ x: 1 }, { x: 2 }]) {
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function f3() {
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~~
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!!! error TS6133: 'f3' is declared but its value is never read.
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x;
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}
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}
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for (let { x } of [{ x: 1 }, { x: 2 }]) {
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let f3 = () => {
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~~
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!!! error TS6133: 'f3' is declared but its value is never read.
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x;
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};
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}
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for (const { x } of [{ x: 1 }, { x: 2 }]) {
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function g3() {
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~~
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!!! error TS6133: 'g3' is declared but its value is never read.
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x;
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}
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}
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‎tests/baselines/reference/unusedLocalsInForInOrOf1.symbols‎

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//// [tests/cases/compiler/unusedLocalsInForInOrOf1.ts] ////
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=== unusedLocalsInForInOrOf1.ts ===
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for (let x of [1, 2]) {
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>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 0, 8))
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function f() {
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>f : Symbol(f, Decl(unusedLocalsInForInOrOf1.ts, 0, 23))
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x;
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>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 0, 8))
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}
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}
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for (let x of [1, 2]) {
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>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 6, 8))
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let f = () => {
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>f : Symbol(f, Decl(unusedLocalsInForInOrOf1.ts, 7, 5))
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x;
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>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 6, 8))
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};
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}
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for (const x of [1, 2]) {
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>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 12, 10))
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function g() {
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>g : Symbol(g, Decl(unusedLocalsInForInOrOf1.ts, 12, 25))
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x;
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>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 12, 10))
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}
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}
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for (let x in { a: 1, b: 2 }) {
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>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 18, 8))
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>a : Symbol(a, Decl(unusedLocalsInForInOrOf1.ts, 18, 15))
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>b : Symbol(b, Decl(unusedLocalsInForInOrOf1.ts, 18, 21))
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function f2() {
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>f2 : Symbol(f2, Decl(unusedLocalsInForInOrOf1.ts, 18, 31))
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x;
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>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 18, 8))
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}
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}
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for (let x in { a: 1, b: 2 }) {
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>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 24, 8))
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>a : Symbol(a, Decl(unusedLocalsInForInOrOf1.ts, 24, 15))
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>b : Symbol(b, Decl(unusedLocalsInForInOrOf1.ts, 24, 21))
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let f2 = () => {
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>f2 : Symbol(f2, Decl(unusedLocalsInForInOrOf1.ts, 25, 5))
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x;
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>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 24, 8))
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};
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}
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for (const x in { a: 1, b: 2 }) {
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>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 30, 10))
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>a : Symbol(a, Decl(unusedLocalsInForInOrOf1.ts, 30, 17))
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>b : Symbol(b, Decl(unusedLocalsInForInOrOf1.ts, 30, 23))
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function g2() {
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>g2 : Symbol(g2, Decl(unusedLocalsInForInOrOf1.ts, 30, 33))
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x;
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>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 30, 10))
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}
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}
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for (let { x } of [{ x: 1 }, { x: 2 }]) {
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>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 36, 10))
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>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 36, 20))
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>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 36, 30))
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function f3() {
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>f3 : Symbol(f3, Decl(unusedLocalsInForInOrOf1.ts, 36, 41))
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x;
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>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 36, 10))
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}
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}
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for (let { x } of [{ x: 1 }, { x: 2 }]) {
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>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 42, 10))
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>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 42, 20))
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>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 42, 30))
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let f3 = () => {
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>f3 : Symbol(f3, Decl(unusedLocalsInForInOrOf1.ts, 43, 5))
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x;
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>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 42, 10))
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};
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}
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for (const { x } of [{ x: 1 }, { x: 2 }]) {
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>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 48, 12))
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>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 48, 22))
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>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 48, 32))
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function g3() {
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>g3 : Symbol(g3, Decl(unusedLocalsInForInOrOf1.ts, 48, 43))
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x;
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>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 48, 12))
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}
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}
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