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Elide import namespace from which only const enums are used (#20320)

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This commit is contained in:
Wesley Wigham
2017-11-29 16:36:17 -08:00
committed by GitHub
parent 78250ec58f
commit a625dec58a
5 changed files with 144 additions and 0 deletions
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14
src/compiler/checker.ts
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@@ -15581,6 +15581,8 @@ namespace ts {
function checkPropertyAccessExpressionOrQualifiedName(node: PropertyAccessExpression | QualifiedName, left: Expression | QualifiedName, right: Identifier) {
let propType: Type;
let leftSymbol = getNodeLinks(left) && getNodeLinks(left).resolvedSymbol;
const leftWasReferenced = leftSymbol && getSymbolLinks(leftSymbol).referenced;
const leftType = checkNonNullExpression(left);
const apparentType = getApparentType(getWidenedType(leftType));
if (isTypeAny(apparentType) || apparentType === silentNeverType) {
@@ -15604,6 +15606,13 @@ namespace ts {
else {
checkPropertyNotUsedBeforeDeclaration(prop, node, right);
markPropertyAsReferenced(prop, node, left.kind === SyntaxKind.ThisKeyword);
// Reset the referenced-ness of the LHS expression if this access refers to a const enum or const enum only module
leftSymbol = getNodeLinks(left) && getNodeLinks(left).resolvedSymbol;
if (leftSymbol && !leftWasReferenced && getSymbolLinks(leftSymbol).referenced &&
!(isNonLocalAlias(leftSymbol, /*excludes*/ SymbolFlags.Value) && !isInTypeQuery(node) && !isConstEnumOrConstEnumOnlyModule(prop))
) {
getSymbolLinks(leftSymbol).referenced = undefined;
}
getNodeLinks(node).resolvedSymbol = prop;
checkPropertyAccessibility(node, left, apparentType, prop);
if (assignmentKind) {
@@ -24691,6 +24700,11 @@ namespace ts {
if (symbol && getSymbolLinks(symbol).referenced) {
return true;
}
const target = getSymbolLinks(symbol).target;
if (target && getModifierFlags(node) & ModifierFlags.Export && target.flags & SymbolFlags.Value) {
// An `export import ... =` of a value symbol is always considered referenced
return true;
}
}
if (checkChildren) {