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Add flag to omit default case in getSwitchClauseTypeOfWitnesses #33574

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Merged
merged 2 commits into from
Mar 10, 2020
Merged

Add flag to omit default case in getSwitchClauseTypeOfWitnesses #33574

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df61cca
Add flag to omit default case
jack-williams Sep 24, 2019
6334a76
Merge remote-tracking branch 'upstream/master' into add-flag-to-getSw…
jack-williams Sep 24, 2019
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11 changes: 6 additions & 5 deletions src/compiler/checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -16911,7 +16911,9 @@ namespace ts {

// Get the types from all cases in a switch on `typeof`. An
// `undefined` element denotes an explicit `default` clause.
function getSwitchClauseTypeOfWitnesses(switchStatement: SwitchStatement): (string | undefined)[] {
function getSwitchClauseTypeOfWitnesses(switchStatement: SwitchStatement, retainDefault: false): string[];
function getSwitchClauseTypeOfWitnesses(switchStatement: SwitchStatement, retainDefault: boolean): (string | undefined)[];
function getSwitchClauseTypeOfWitnesses(switchStatement: SwitchStatement, retainDefault: boolean): (string | undefined)[] {
const witnesses: (string | undefined)[] = [];
for (const clause of switchStatement.caseBlock.clauses) {
if (clause.kind === SyntaxKind.CaseClause) {
Expand All @@ -16921,7 +16923,7 @@ namespace ts {
}
return emptyArray;
}
witnesses.push(/*explicitDefaultStatement*/ undefined);
if (retainDefault) witnesses.push(/*explicitDefaultStatement*/ undefined);
}
return witnesses;
}
Expand Down Expand Up @@ -17937,7 +17939,7 @@ namespace ts {
}

function narrowBySwitchOnTypeOf(type: Type, switchStatement: SwitchStatement, clauseStart: number, clauseEnd: number): Type {
const switchWitnesses = getSwitchClauseTypeOfWitnesses(switchStatement);
const switchWitnesses = getSwitchClauseTypeOfWitnesses(switchStatement, /*retainDefault*/ true);
if (!switchWitnesses.length) {
return type;
}
Expand Down Expand Up @@ -24017,8 +24019,7 @@ namespace ts {
function computeExhaustiveSwitchStatement(node: SwitchStatement): boolean {
if (node.expression.kind === SyntaxKind.TypeOfExpression) {
const operandType = getTypeOfExpression((node.expression as TypeOfExpression).expression);
// This cast is safe because the switch is possibly exhaustive and does not contain a default case, so there can be no undefined.
const witnesses = <string[]>getSwitchClauseTypeOfWitnesses(node);
const witnesses = getSwitchClauseTypeOfWitnesses(node, /*retainDefault*/ false);
// notEqualFacts states that the type of the switched value is not equal to every type in the switch.
const notEqualFacts = getFactsFromTypeofSwitch(0, 0, witnesses, /*hasDefault*/ true);
const type = getBaseConstraintOfType(operandType) || operandType;
Expand Down