Normative: Extend definition of "function code" (tc39#1158)

In the March 2018 meeting of TC39, the committee elected to extend the
definition of "function code" to include the BindingIdentifier of the
productions where a BindingIdentifier is present. This decision was
motivated by a desire to match implementation reality.

This alteration does not require a change to Test262 because like the
majority of modern implementations, Test262 already enforces the new
behavior [1].

[1] tc39/test262#1404

spec.html

@@ -9383,7 +9383,15 @@ <h1>Types of Source Code</h1>
         <em>Eval code</em> is the source text supplied to the built-in `eval` function. More precisely, if the parameter to the built-in `eval` function is a String, it is treated as an ECMAScript |Script|. The eval code for a particular invocation of `eval` is the global code portion of that |Script|.
       </li>
       <li>
-        <em>Function code</em> is source text that is parsed to supply the value of the [[ECMAScriptCode]] and [[FormalParameters]] internal slots (see <emu-xref href="#sec-ecmascript-function-objects"></emu-xref>) of an ECMAScript function object. The function code of a particular ECMAScript function does not include any source text that is parsed as the function code of a nested |FunctionDeclaration|, |FunctionExpression|, |GeneratorDeclaration|, |GeneratorExpression|, |AsyncFunctionDeclaration|, |AsyncFunctionExpression|, |AsyncGeneratorDeclaration|, |AsyncGeneratorExpression|, |MethodDefinition|, |ArrowFunction|, |AsyncArrowFunction|, |ClassDeclaration|, or |ClassExpression|.
+        <p><em>Function code</em> is source text that is parsed to supply the value of the [[ECMAScriptCode]] and [[FormalParameters]] internal slots (see <emu-xref href="#sec-ecmascript-function-objects"></emu-xref>) of an ECMAScript function object. The function code of a particular ECMAScript function does not include any source text that is parsed as the function code of a nested |FunctionDeclaration|, |FunctionExpression|, |GeneratorDeclaration|, |GeneratorExpression|, |AsyncFunctionDeclaration|, |AsyncFunctionExpression|, |AsyncGeneratorDeclaration|, |AsyncGeneratorExpression|, |MethodDefinition|, |ArrowFunction|, |AsyncArrowFunction|, |ClassDeclaration|, or |ClassExpression|.</p>
+        <p>In addition, if the source text referred to above is parsed as:</p>
+        <ul>
+          <li>the |FormalParameters| and |FunctionBody| of a |FunctionDeclaration| or |FunctionExpression|,</li>
+          <li>the |FormalParameters| and |GeneratorBody| of a |GeneratorDeclaration| or |GeneratorExpression|,</li>
+          <li>the |FormalParameters| and |AsyncFunctionBody| of an |AsyncFunctionDeclaration| or |AsyncFunctionExpression|, or</li>
+          <li>the |FormalParameters| and |AsyncGeneratorBody| of an |AsyncGeneratorDeclaration| or |AsyncGeneratorExpression|,</li>
+        </ul>
+        <p>then the source text matching the |BindingIdentifier| (if any) of that declaration or expression is also included in the function code of the corresponding function.</p>
       </li>
       <li>
         <em>Module code</em> is source text that is code that is provided as a |ModuleBody|. It is the code that is directly evaluated when a module is initialized. The module code of a particular module does not include any source text that is parsed as part of a nested |FunctionDeclaration|, |FunctionExpression|, |GeneratorDeclaration|, |GeneratorExpression|, |AsyncFunctionDeclaration|, |AsyncFunctionExpression|, |AsyncGeneratorDeclaration|, |AsyncGeneratorExpression|, |MethodDefinition|, |ArrowFunction|, |AsyncArrowFunction|, |ClassDeclaration|, or |ClassExpression|.
@@ -9392,6 +9400,9 @@ <h1>Types of Source Code</h1>
     <emu-note>
       <p>Function code is generally provided as the bodies of Function Definitions (<emu-xref href="#sec-function-definitions"></emu-xref>), Arrow Function Definitions (<emu-xref href="#sec-arrow-function-definitions"></emu-xref>), Method Definitions (<emu-xref href="#sec-method-definitions"></emu-xref>), Generator Function Definitions (<emu-xref href="#sec-generator-function-definitions"></emu-xref>), Async Function Definitions (<emu-xref href="#sec-async-function-definitions"></emu-xref>), Async Generator Function Definitions (<emu-xref href="#sec-async-generator-function-definitions"></emu-xref>), and Async Arrow Functions (<emu-xref href="#sec-async-arrow-function-definitions"></emu-xref>). Function code is also derived from the arguments to the `Function` constructor (<emu-xref href="#sec-function-p1-p2-pn-body"></emu-xref>), the `GeneratorFunction` constructor (<emu-xref href="#sec-generatorfunction"></emu-xref>), and the `AsyncFunction` constructor (<emu-xref href="#sec-async-function-constructor-arguments"></emu-xref>).</p>
     </emu-note>
+    <emu-note>
+      <p>The practical effect of including the |BindingIdentifier| in function code is that the Early Errors for strict mode code are applied to a |BindingIdentifier| that is the name of a function whose body contains a "use strict" directive, even if the surrounding code is not strict mode code.</p>
+    </emu-note>
 
     <emu-clause id="sec-strict-mode-code">
       <h1>Strict Mode Code</h1>