v8/test/mjsunit/declare-locally.js

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// Make sure that we're not overwriting global
// properties defined in the prototype chain too
// early when shadowing them with var/const
// declarations.

// This exercises the code in runtime.cc in
// DeclareGlobal...Locally().

// Flags: --legacy-const

this.__proto__.foo = 42;
this.__proto__.bar = 87;

eval("assertEquals(undefined, foo); var foo = 87;");
assertEquals(87, foo);

eval("assertEquals(undefined, bar); const bar = 42;");
assertEquals(42, bar);