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diff --git a/js/src/tests/non262/Intl/unicode-bcp47-locale-ids-variants-legacy-mappings.js b/js/src/tests/non262/Intl/unicode-bcp47-locale-ids-variants-legacy-mappings.js
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+++ b/js/src/tests/non262/Intl/unicode-bcp47-locale-ids-variants-legacy-mappings.js
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+// |reftest| skip-if(!this.hasOwnProperty("Intl"))
+
+// ECMA-402 includes mapping of legacy variants, as long as they're also present
+// in <variantAlias> in CLDR's supplementalMetadata.xml
+// <https://www.unicode.org/reports/tr35/#Legacy_Variants>
+
+assertEq(Intl.getCanonicalLocales("sv-AALAND")[0], "sv-AX");
+assertEq(Intl.getCanonicalLocales("no-BOKMAL")[0], "nb");
+assertEq(Intl.getCanonicalLocales("no-NYNORSK")[0], "nn");
+assertEq(Intl.getCanonicalLocales("en-POSIX")[0], "en-posix");
+assertEq(Intl.getCanonicalLocales("el-POLYTONI")[0], "el-polyton");
+assertEq(Intl.getCanonicalLocales("aa-SAAHO")[0], "ssy");
+
+// Additional cases from CLDR, version 38.
+
+assertEq(Intl.getCanonicalLocales("aar-saaho")[0], "ssy");
+assertEq(Intl.getCanonicalLocales("arm-arevmda")[0], "hyw");
+assertEq(Intl.getCanonicalLocales("hy-arevmda")[0], "hyw");
+assertEq(Intl.getCanonicalLocales("hye-arevmda")[0], "hyw");
+
+for (let language of ["chi", "cmn", "zh", "zho"]) {
+    assertEq(Intl.getCanonicalLocales(language)[0], "zh");
+
+    let mapping = {
+        "guoyu-hakka": "hak",
+        "guoyu-xiang": "hsn",
+        "guoyu": "zh",
+        "hakka": "hak",
+        "xiang": "hsn",
+    };
+    for (let [variant, canonical] of Object.entries(mapping)) {
+        assertEq(Intl.getCanonicalLocales(`${language}-${variant}`)[0], canonical);
+    }
+}
+
+// Most legacy variant subtags are simply removed in contexts they don't apply.
+for (let variant of ["arevela", "arevmda", "bokmal", "hakka", "lojban", "nynorsk", "saaho", "xiang"]) {
+    assertEq(Intl.getCanonicalLocales(`en-${variant}`)[0], "en");
+}
+
+// Except these three, whose replacement is always applied.
+assertEq(Intl.getCanonicalLocales("en-aaland")[0], "en-AX");
+assertEq(Intl.getCanonicalLocales("en-heploc")[0], "en-alalc97");
+assertEq(Intl.getCanonicalLocales("en-polytoni")[0], "en-polyton");
+
+if (typeof reportCompare === "function")
+    reportCompare(true, true);