Class fields, part 3 (backends)

src/compiler/ast-graph-builder.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/ast-graph-builder.h"
 
 #include "src/ast/compile-time-value.h"
 #include "src/ast/scopes.h"
 #include "src/compilation-info.h"
 #include "src/compiler.h"
@@ skipping 1573 matching lines @@
   Node* constructor = environment()->Pop();
   Node* extends = environment()->Pop();
   Node* start = jsgraph()->Constant(expr->start_position());
   Node* end = jsgraph()->Constant(expr->end_position());
   const Operator* opc = javascript()->CallRuntime(Runtime::kDefineClass);
   Node* literal = NewNode(opc, extends, constructor, start, end);
   PrepareFrameState(literal, expr->CreateLiteralId(),
                     OutputFrameStateCombine::Push());
   environment()->Push(literal);
 
+  // The below proxy exists to allow static field initializers to have the
+  // correct home object and receiver. It's only necessary if the initializers
+  // are called as a part of class definition instead of immediately after it,
+  // in which case they could simply refer to the class just constructed. The
+  // latter is actually what's currently specified, and this will need to be
+  // changed if that behavior is settled upon. See also
+  // https://github.com/tc39/proposal-class-public-fields/issues/50
+  VariableProxy* static_initializer_proxy = expr->static_initializer_proxy();
+  if (static_initializer_proxy != nullptr) {
+    Variable* variable = static_initializer_proxy->var();
+    BuildVariableAssignment(variable, literal, Token::INIT,
+                            CreateVectorSlotPair(FeedbackVectorSlot::Invalid()),
+                            BailoutId::None());
+  }
+
   // Load the "prototype" from the constructor.
   PrepareEagerCheckpoint(expr->CreateLiteralId());
   Handle<Name> name = isolate()->factory()->prototype_string();
   VectorSlotPair pair = CreateVectorSlotPair(expr->PrototypeSlot());
   Node* prototype = BuildNamedLoad(literal, name, pair);
   PrepareFrameState(prototype, expr->PrototypeId(),
                     OutputFrameStateCombine::Push());
   environment()->Push(prototype);
 
   // Create nodes to store method values into the literal.
   for (int i = 0; i < expr->properties()->length(); i++) {
     ClassLiteral::Property* property = expr->properties()->at(i);
+
+    if (property->kind() == ClassLiteral::Property::FIELD &&
+        !property->is_static()) {
+      // Non-static properties produced by the parser have as their 'key' an
+      // expression producing their name and as their 'value' a variable which
+      // is refered to by the synthetic initializer function in order to
+      // determine the name during class instantiation. This is necessary
+      // because computed names must only be evaluated once, at class definition
+      // time.
+      // That is, code which looks like `class C { [f()] = 1; }` is desugared
+      // into something like
+      // class C { constructor(){ this.[.class-field-0-name] = 1; } };
+      // let .class-field-0-name = f();
+      // except that the assignment to .class-field-name-0 occurs interleaved
+      // with the rest of the class body; it is performed by the block in which
+      // this comment appears.
+      Variable* variable = property->value()->AsVariableProxy()->var();
+      VisitForValue(property->key());
+      Node* key = environment()->Pop();
+      BuildVariableAssignment(
+          variable, key, Token::INIT,
+          CreateVectorSlotPair(FeedbackVectorSlot::Invalid()),
+          BailoutId::None());
+      continue;
+    }
+
     environment()->Push(environment()->Peek(property->is_static() ? 1 : 0));
 
     VisitForValue(property->key());
     Node* name = BuildToName(environment()->Pop(), expr->GetIdForProperty(i));
     environment()->Push(name);
 
     // The static prototype property is read only. We handle the non computed
     // property name case in the parser. Since this is the only case where we
     // need to check for an own read only property we special case this so we do
     // not need to do this for every property.
@@ skipping 29 matching lines @@
         break;
       }
       case ClassLiteral::Property::SETTER: {
         Node* attr = jsgraph()->Constant(DONT_ENUM);
         const Operator* op = javascript()->CallRuntime(
             Runtime::kDefineSetterPropertyUnchecked, 4);
         NewNode(op, receiver, key, value, attr);
         break;
       }
       case ClassLiteral::Property::FIELD: {
-        UNREACHABLE();
+        DCHECK(property->is_static());
+        Node* attr = jsgraph()->Constant(DONT_ENUM);
+        Node* set_function_name =
+            jsgraph()->Constant(property->NeedsSetFunctionName());
+        const Operator* op =
+            javascript()->CallRuntime(Runtime::kDefineDataPropertyInLiteral);
+        Node* call = NewNode(op, receiver, key, value, attr, set_function_name);
+        PrepareFrameState(call, BailoutId::None());
         break;
       }
     }
   }
 
   // Set the constructor to have fast properties.
   prototype = environment()->Pop();
   literal = environment()->Pop();
   const Operator* op = javascript()->CallRuntime(Runtime::kToFastProperties);
   literal = NewNode(op, literal);
@@ skipping 2667 matching lines @@
     // Phi does not exist yet, introduce one.
     value = NewPhi(inputs, value, control);
     value->ReplaceInput(inputs - 1, other);
   }
   return value;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8