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Merge pull request #10235 from Microsoft/fixDiscriminantWithNullableType
Fix discriminant type guards with nullable type
2 parents 3f1ec7a + 6c0bca0 commit 557fc38

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5 files changed

+209
-8
lines changed

5 files changed

+209
-8
lines changed

‎src/compiler/checker.ts

Lines changed: 11 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -7837,14 +7837,17 @@ namespace ts {
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}
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function isDiscriminantProperty(type: Type, name: string) {
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if (type && type.flags & TypeFlags.Union) {
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const prop = getPropertyOfType(type, name);
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if (prop && prop.flags & SymbolFlags.SyntheticProperty) {
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if ((<TransientSymbol>prop).isDiscriminantProperty === undefined) {
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(<TransientSymbol>prop).isDiscriminantProperty = !(<TransientSymbol>prop).hasCommonType &&
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isUnitUnionType(getTypeOfSymbol(prop));
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}
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return (<TransientSymbol>prop).isDiscriminantProperty;
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if (type) {
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const nonNullType = getNonNullableType(type);
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if (nonNullType.flags & TypeFlags.Union) {
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const prop = getPropertyOfType(nonNullType, name);
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if (prop && prop.flags & SymbolFlags.SyntheticProperty) {
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if ((<TransientSymbol>prop).isDiscriminantProperty === undefined) {
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(<TransientSymbol>prop).isDiscriminantProperty = !(<TransientSymbol>prop).hasCommonType &&
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isUnitUnionType(getTypeOfSymbol(prop));
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}
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return (<TransientSymbol>prop).isDiscriminantProperty;
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}
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}
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}
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return false;

‎tests/baselines/reference/discriminantsAndNullOrUndefined.js

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//// [discriminantsAndNullOrUndefined.ts]
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// Repro from #10228
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interface A { kind: 'A'; }
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interface B { kind: 'B'; }
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type C = A | B | undefined;
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function never(_: never): never {
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throw new Error();
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}
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function useA(_: A): void { }
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function useB(_: B): void { }
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declare var c: C;
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if (c !== undefined) {
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switch (c.kind) {
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case 'A': useA(c); break;
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case 'B': useB(c); break;
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default: never(c);
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}
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}
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//// [discriminantsAndNullOrUndefined.js]
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// Repro from #10228
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function never(_) {
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throw new Error();
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}
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function useA(_) { }
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function useB(_) { }
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if (c !== undefined) {
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switch (c.kind) {
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case 'A':
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useA(c);
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break;
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case 'B':
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useB(c);
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break;
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default: never(c);
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}
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}

‎tests/baselines/reference/discriminantsAndNullOrUndefined.symbols

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=== tests/cases/compiler/discriminantsAndNullOrUndefined.ts ===
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// Repro from #10228
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interface A { kind: 'A'; }
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>A : Symbol(A, Decl(discriminantsAndNullOrUndefined.ts, 0, 0))
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>kind : Symbol(A.kind, Decl(discriminantsAndNullOrUndefined.ts, 3, 13))
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interface B { kind: 'B'; }
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>B : Symbol(B, Decl(discriminantsAndNullOrUndefined.ts, 3, 26))
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>kind : Symbol(B.kind, Decl(discriminantsAndNullOrUndefined.ts, 4, 13))
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type C = A | B | undefined;
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>C : Symbol(C, Decl(discriminantsAndNullOrUndefined.ts, 4, 26))
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>A : Symbol(A, Decl(discriminantsAndNullOrUndefined.ts, 0, 0))
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>B : Symbol(B, Decl(discriminantsAndNullOrUndefined.ts, 3, 26))
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function never(_: never): never {
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>never : Symbol(never, Decl(discriminantsAndNullOrUndefined.ts, 6, 27))
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>_ : Symbol(_, Decl(discriminantsAndNullOrUndefined.ts, 8, 15))
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throw new Error();
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>Error : Symbol(Error, Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --))
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}
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function useA(_: A): void { }
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>useA : Symbol(useA, Decl(discriminantsAndNullOrUndefined.ts, 10, 1))
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>_ : Symbol(_, Decl(discriminantsAndNullOrUndefined.ts, 12, 14))
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>A : Symbol(A, Decl(discriminantsAndNullOrUndefined.ts, 0, 0))
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function useB(_: B): void { }
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>useB : Symbol(useB, Decl(discriminantsAndNullOrUndefined.ts, 12, 29))
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>_ : Symbol(_, Decl(discriminantsAndNullOrUndefined.ts, 13, 14))
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>B : Symbol(B, Decl(discriminantsAndNullOrUndefined.ts, 3, 26))
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declare var c: C;
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>c : Symbol(c, Decl(discriminantsAndNullOrUndefined.ts, 15, 11))
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>C : Symbol(C, Decl(discriminantsAndNullOrUndefined.ts, 4, 26))
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if (c !== undefined) {
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>c : Symbol(c, Decl(discriminantsAndNullOrUndefined.ts, 15, 11))
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>undefined : Symbol(undefined)
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switch (c.kind) {
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>c.kind : Symbol(kind, Decl(discriminantsAndNullOrUndefined.ts, 3, 13), Decl(discriminantsAndNullOrUndefined.ts, 4, 13))
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>c : Symbol(c, Decl(discriminantsAndNullOrUndefined.ts, 15, 11))
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>kind : Symbol(kind, Decl(discriminantsAndNullOrUndefined.ts, 3, 13), Decl(discriminantsAndNullOrUndefined.ts, 4, 13))
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case 'A': useA(c); break;
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>useA : Symbol(useA, Decl(discriminantsAndNullOrUndefined.ts, 10, 1))
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>c : Symbol(c, Decl(discriminantsAndNullOrUndefined.ts, 15, 11))
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case 'B': useB(c); break;
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>useB : Symbol(useB, Decl(discriminantsAndNullOrUndefined.ts, 12, 29))
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>c : Symbol(c, Decl(discriminantsAndNullOrUndefined.ts, 15, 11))
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default: never(c);
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>never : Symbol(never, Decl(discriminantsAndNullOrUndefined.ts, 6, 27))
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>c : Symbol(c, Decl(discriminantsAndNullOrUndefined.ts, 15, 11))
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}
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}

‎tests/baselines/reference/discriminantsAndNullOrUndefined.types

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=== tests/cases/compiler/discriminantsAndNullOrUndefined.ts ===
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// Repro from #10228
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interface A { kind: 'A'; }
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>A : A
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>kind : "A"
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interface B { kind: 'B'; }
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>B : B
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>kind : "B"
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type C = A | B | undefined;
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>C : C
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>A : A
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>B : B
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function never(_: never): never {
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>never : (_: never) => never
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>_ : never
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throw new Error();
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>new Error() : Error
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>Error : ErrorConstructor
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}
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function useA(_: A): void { }
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>useA : (_: A) => void
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>_ : A
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>A : A
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function useB(_: B): void { }
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>useB : (_: B) => void
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>_ : B
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>B : B
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declare var c: C;
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>c : C
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>C : C
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if (c !== undefined) {
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>c !== undefined : boolean
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>c : C
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>undefined : undefined
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switch (c.kind) {
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>c.kind : "A" | "B"
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>c : A | B
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>kind : "A" | "B"
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case 'A': useA(c); break;
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>'A' : "A"
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>useA(c) : void
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>useA : (_: A) => void
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>c : A
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case 'B': useB(c); break;
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>'B' : "B"
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>useB(c) : void
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>useB : (_: B) => void
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>c : B
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default: never(c);
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>never(c) : never
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>never : (_: never) => never
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>c : never
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}
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}

‎tests/cases/compiler/discriminantsAndNullOrUndefined.ts

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// @strictNullChecks: true
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// Repro from #10228
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interface A { kind: 'A'; }
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interface B { kind: 'B'; }
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type C = A | B | undefined;
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function never(_: never): never {
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throw new Error();
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}
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function useA(_: A): void { }
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function useB(_: B): void { }
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declare var c: C;
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if (c !== undefined) {
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switch (c.kind) {
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case 'A': useA(c); break;
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case 'B': useB(c); break;
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default: never(c);
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}
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}

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