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Use declared type for references in unreachable code

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This commit is contained in:
Anders Hejlsberg 2019-09-12 07:41:47 -07:00
parent 5a180bac03
commit 436339ddef
1 changed files with 12 additions and 4 deletions
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16
src/compiler/checker.ts
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@ -671,6 +671,7 @@ namespace ts {
const silentNeverType = createIntrinsicType(TypeFlags.Never, "never");
const nonInferrableType = createIntrinsicType(TypeFlags.Never, "never", ObjectFlags.NonInferrableType);
const implicitNeverType = createIntrinsicType(TypeFlags.Never, "never");
const unreachableNeverType = createIntrinsicType(TypeFlags.Never, "never");
const nonPrimitiveType = createIntrinsicType(TypeFlags.NonPrimitive, "object");
const stringNumberSymbolType = getUnionType([stringType, numberType, esSymbolType]);
const keyofConstraintType = keyofStringsOnly ? stringType : stringNumberSymbolType;
@ -17008,7 +17009,7 @@ namespace ts {
// on empty arrays are possible without implicit any errors and new element types can be inferred without
// type mismatch errors.
const resultType = getObjectFlags(evolvedType) & ObjectFlags.EvolvingArray && isEvolvingArrayOperationTarget(reference) ? autoArrayType : finalizeEvolvingArrayType(evolvedType);
if (reference.parent && reference.parent.kind === SyntaxKind.NonNullExpression && getTypeWithFacts(resultType, TypeFacts.NEUndefinedOrNull).flags & TypeFlags.Never) {
if (resultType === unreachableNeverType || reference.parent && reference.parent.kind === SyntaxKind.NonNullExpression && getTypeWithFacts(resultType, TypeFacts.NEUndefinedOrNull).flags & TypeFlags.Never) {
return declaredType;
}
return resultType;
@ -17144,8 +17145,11 @@ namespace ts {
// Assignments only narrow the computed type if the declared type is a union type. Thus, we
// only need to evaluate the assigned type if the declared type is a union type.
if (isMatchingReference(reference, node)) {
const flowType = getTypeAtFlowNode(flow.antecedent);
if (flowType === unreachableNeverType) {
return flowType;
}
if (getAssignmentTargetKind(node) === AssignmentKind.Compound) {
const flowType = getTypeAtFlowNode(flow.antecedent);
return createFlowType(getBaseTypeOfLiteralType(getTypeFromFlowType(flowType)), isIncomplete(flowType));
}
if (declaredType === autoType || declaredType === autoArrayType) {
@ -17165,12 +17169,16 @@ namespace ts {
// reference 'x.y.z', we may be at an assignment to 'x.y' or 'x'. In that case,
// return the declared type.
if (containsMatchingReference(reference, node)) {
const flowType = getTypeAtFlowNode(flow.antecedent);
if (flowType === unreachableNeverType) {
return flowType;
}
// A matching dotted name might also be an expando property on a function *expression*,
// in which case we continue control flow analysis back to the function's declaration
if (isVariableDeclaration(node) && (isInJSFile(node) || isVarConst(node))) {
const init = getDeclaredExpandoInitializer(node);
if (init && (init.kind === SyntaxKind.FunctionExpression || init.kind === SyntaxKind.ArrowFunction)) {
return getTypeAtFlowNode(flow.antecedent);
return flowType;
}
}
return declaredType;
@ -17209,7 +17217,7 @@ namespace ts {
return narrowedType === type ? flowType : createFlowType(narrowedType, isIncomplete(flowType));
}
if (getReturnTypeOfSignature(signature).flags & TypeFlags.Never) {
return neverType;
return unreachableNeverType;
}
}
return undefined;