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There is a newer version: 18.2.12
/**
 * @license
 * Copyright Google LLC All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */
import { assertIndexInRange, assertLessThan, assertNotSame } from '../util/assert';
import { devModeEqual } from '../util/comparison';
import { getExpressionChangedErrorDetails, throwErrorIfNoChangesMode } from './errors';
import { isInCheckNoChangesMode } from './state';
import { NO_CHANGE } from './tokens';
// TODO(misko): consider inlining
/** Updates binding and returns the value. */
export function updateBinding(lView, bindingIndex, value) {
    return (lView[bindingIndex] = value);
}
/** Gets the current binding value. */
export function getBinding(lView, bindingIndex) {
    ngDevMode && assertIndexInRange(lView, bindingIndex);
    ngDevMode &&
        assertNotSame(lView[bindingIndex], NO_CHANGE, 'Stored value should never be NO_CHANGE.');
    return lView[bindingIndex];
}
/**
 * Updates binding if changed, then returns whether it was updated.
 *
 * This function also checks the `CheckNoChangesMode` and throws if changes are made.
 * Some changes (Objects/iterables) during `CheckNoChangesMode` are exempt to comply with VE
 * behavior.
 *
 * @param lView current `LView`
 * @param bindingIndex The binding in the `LView` to check
 * @param value New value to check against `lView[bindingIndex]`
 * @returns `true` if the bindings has changed. (Throws if binding has changed during
 *          `CheckNoChangesMode`)
 */
export function bindingUpdated(lView, bindingIndex, value) {
    ngDevMode && assertNotSame(value, NO_CHANGE, 'Incoming value should never be NO_CHANGE.');
    ngDevMode &&
        assertLessThan(bindingIndex, lView.length, `Slot should have been initialized to NO_CHANGE`);
    const oldValue = lView[bindingIndex];
    if (Object.is(oldValue, value)) {
        return false;
    }
    else {
        if (ngDevMode && isInCheckNoChangesMode()) {
            // View engine didn't report undefined values as changed on the first checkNoChanges pass
            // (before the change detection was run).
            const oldValueToCompare = oldValue !== NO_CHANGE ? oldValue : undefined;
            if (!devModeEqual(oldValueToCompare, value)) {
                const details = getExpressionChangedErrorDetails(lView, bindingIndex, oldValueToCompare, value);
                throwErrorIfNoChangesMode(oldValue === NO_CHANGE, details.oldValue, details.newValue, details.propName, lView);
            }
            // There was a change, but the `devModeEqual` decided that the change is exempt from an error.
            // For this reason we exit as if no change. The early exit is needed to prevent the changed
            // value to be written into `LView` (If we would write the new value that we would not see it
            // as change on next CD.)
            return false;
        }
        lView[bindingIndex] = value;
        return true;
    }
}
/** Updates 2 bindings if changed, then returns whether either was updated. */
export function bindingUpdated2(lView, bindingIndex, exp1, exp2) {
    const different = bindingUpdated(lView, bindingIndex, exp1);
    return bindingUpdated(lView, bindingIndex + 1, exp2) || different;
}
/** Updates 3 bindings if changed, then returns whether any was updated. */
export function bindingUpdated3(lView, bindingIndex, exp1, exp2, exp3) {
    const different = bindingUpdated2(lView, bindingIndex, exp1, exp2);
    return bindingUpdated(lView, bindingIndex + 2, exp3) || different;
}
/** Updates 4 bindings if changed, then returns whether any was updated. */
export function bindingUpdated4(lView, bindingIndex, exp1, exp2, exp3, exp4) {
    const different = bindingUpdated2(lView, bindingIndex, exp1, exp2);
    return bindingUpdated2(lView, bindingIndex + 2, exp3, exp4) || different;
}
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(Throws if binding has changed during\n *          `CheckNoChangesMode`)\n */\nexport function bindingUpdated(lView: LView, bindingIndex: number, value: any): boolean {\n  ngDevMode && assertNotSame(value, NO_CHANGE, 'Incoming value should never be NO_CHANGE.');\n  ngDevMode &&\n    assertLessThan(bindingIndex, lView.length, `Slot should have been initialized to NO_CHANGE`);\n  const oldValue = lView[bindingIndex];\n\n  if (Object.is(oldValue, value)) {\n    return false;\n  } else {\n    if (ngDevMode && isInCheckNoChangesMode()) {\n      // View engine didn't report undefined values as changed on the first checkNoChanges pass\n      // (before the change detection was run).\n      const oldValueToCompare = oldValue !== NO_CHANGE ? oldValue : undefined;\n      if (!devModeEqual(oldValueToCompare, value)) {\n        const details = getExpressionChangedErrorDetails(\n          lView,\n          bindingIndex,\n          oldValueToCompare,\n          value,\n        );\n        throwErrorIfNoChangesMode(\n          oldValue === NO_CHANGE,\n          details.oldValue,\n          details.newValue,\n          details.propName,\n          lView,\n        );\n      }\n      // There was a change, but the `devModeEqual` decided that the change is exempt from an error.\n      // For this reason we exit as if no change. The early exit is needed to prevent the changed\n      // value to be written into `LView` (If we would write the new value that we would not see it\n      // as change on next CD.)\n      return false;\n    }\n    lView[bindingIndex] = value;\n    return true;\n  }\n}\n\n/** Updates 2 bindings if changed, then returns whether either was updated. */\nexport function bindingUpdated2(lView: LView, bindingIndex: number, exp1: any, exp2: any): boolean {\n  const different = bindingUpdated(lView, bindingIndex, exp1);\n  return bindingUpdated(lView, bindingIndex + 1, exp2) || different;\n}\n\n/** Updates 3 bindings if changed, then returns whether any was updated. */\nexport function bindingUpdated3(\n  lView: LView,\n  bindingIndex: number,\n  exp1: any,\n  exp2: any,\n  exp3: any,\n): boolean {\n  const different = bindingUpdated2(lView, bindingIndex, exp1, exp2);\n  return bindingUpdated(lView, bindingIndex + 2, exp3) || different;\n}\n\n/** Updates 4 bindings if changed, then returns whether any was updated. */\nexport function bindingUpdated4(\n  lView: LView,\n  bindingIndex: number,\n  exp1: any,\n  exp2: any,\n  exp3: any,\n  exp4: any,\n): boolean {\n  const different = bindingUpdated2(lView, bindingIndex, exp1, exp2);\n  return bindingUpdated2(lView, bindingIndex + 2, exp3, exp4) || different;\n}\n"]}