1216630 - Print class source when calling toString on the constructor.

This is accomplished in the following ways.
LazyScripts and JSScripts now have 4 offsets:
- Source begin and end for the actual source. This is used for lazy parsing.

- toString begin and end for toString. Some kinds of functions, like async, only have a different begin offset. Class constructors have different offsets for both begin and end.

For syntactically present (i.e. non-default) constructors, the class source span is remembered directly on the LazyScript or JSScript. The toString implementation then splices out the substring directly. For default constructors, a new SRC_CLASS SrcNote type is added. It's binary and has as its arguments the begin and end offsets of the class expression or statement. MakeDefaultConstructor reads the note and overrides the cloned self-hosted function's source object. This is probably the least intrusive way to accomplish this.

1 files changed, 11 insertions, 5 deletions

diff --git a/js/src/frontend/BytecodeCompiler.cpp b/js/src/frontend/BytecodeCompiler.cpp
index a4b7dba6b0..e0bb64e051 100644
--- a/js/src/frontend/BytecodeCompiler.cpp
+++ b/js/src/frontend/BytecodeCompiler.cpp
@@ -77,7 +77,13 @@ class MOZ_STACK_CLASS BytecodeCompiler
     bool canLazilyParse();
     bool createParser();
     bool createSourceAndParser(Maybe<uint32_t> parameterListEnd = Nothing());
-    bool createScript(uint32_t preludeStart = 0);
+
+    // If toString{Start,End} are not explicitly passed, assume the script's
+    // offsets in the source used to parse it are the same as what should be
+    // used to compute its Function.prototype.toString() value.
+    bool createScript();
+    bool createScript(uint32_t toStringStart, uint32_t toStringEnd);
+
     bool emplaceEmitter(Maybe<BytecodeEmitter>& emitter, SharedContext* sharedContext);
     bool handleParseFailure(const Directives& newDirectives);
     bool deoptimizeArgumentsInEnclosingScripts(JSContext* cx, HandleObject environment);
@@ -242,11 +248,11 @@ BytecodeCompiler::createSourceAndParser(Maybe<uint32_t> parameterListEnd /* = No
 }
 
 bool
-BytecodeCompiler::createScript(uint32_t preludeStart /* = 0 */)
+BytecodeCompiler::createScript(uint32_t preludeStart /* = 0 */, uint32_t postludeEnd /* = 0 */)
 {
     script = JSScript::Create(cx, options,
                               sourceObject, /* sourceStart = */ 0, sourceBuffer.length(),
-                              preludeStart);
+                              preludeStart, postludeEnd);
     return script != nullptr;
 }
 
@@ -458,7 +464,7 @@ BytecodeCompiler::compileStandaloneFunction(MutableHandleFunction fun,
     if (fn->pn_funbox->function()->isInterpreted()) {
         MOZ_ASSERT(fun == fn->pn_funbox->function());
 
-        if (!createScript(fn->pn_funbox->preludeStart))
+        if (!createScript(fn->pn_funbox->preludeStart, fn->pn_funbox->postludeEnd))
             return false;
 
         Maybe<BytecodeEmitter> emitter;
@@ -653,7 +659,7 @@ frontend::CompileLazyFunction(JSContext* cx, Handle<LazyScript*> lazy, const cha
 
     Rooted<JSScript*> script(cx, JSScript::Create(cx, options, sourceObject,
                                                   lazy->begin(), lazy->end(),
-                                                  lazy->preludeStart()));
+                                                  lazy->preludeStart(), lazy->postludeEnd()));
     if (!script)
         return false;