Add some support for the code-point code-unit distinction.

sdk/lib/_internal/compiler/implementation/js_backend/constant_emitter.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of js_backend;
 
 class ConstantEmitter implements ConstantVisitor {
   final Compiler compiler;
   final Namer namer;
 
@@ skipping 66 matching lines @@
   }
 
   void visitTrue(TrueConstant constant) {
     buffer.add("true");
   }
 
   void visitFalse(FalseConstant constant) {
     buffer.add("false");
   }
 
+  void addHexEscape(CodeBuffer buffer, int code) {
+    assert(code < 0x10000);
+    if (code < 0x20) {
+      buffer.add(r'\x');
+      if (code < 0x10) buffer.add('0');
+      buffer.add(code.toRadixString(16));
+    } else {
+      if (code < 0x100) {
+        assert(code >= 0x80);
+        buffer.add(r'\x');
+      } else {
+        buffer.add(r'\u');
+        if (code < 0x1000) {
+          buffer.add('0');
+        }
+      }
+      buffer.add(code.toRadixString(16));
+    }
+  }
+
   /**
    * Write the contents of the quoted string to a [CodeBuffer] in
    * a form that is valid as JavaScript string literal content.
    * The string is assumed quoted by single quote characters.
    */
   void writeEscapedString(DartString string,
                           CodeBuffer buffer,
                           Node diagnosticNode) {
     Iterator<int> iterator = string.iterator();
     while (iterator.hasNext) {
       int code = iterator.next();
       if (identical(code, $SQ)) {
         buffer.add(r"\'");
       } else if (identical(code, $LF)) {
         buffer.add(r'\n');
       } else if (identical(code, $CR)) {
         buffer.add(r'\r');
       } else if (identical(code, $LS)) {
         // This Unicode line terminator and $PS are invalid in JS string
         // literals.
-        buffer.add(r'\u2028');
+        addHexEscape(buffer, 0x2028);
       } else if (identical(code, $PS)) {
-        buffer.add(r'\u2029');
+        addHexEscape(buffer, 0x2029);
       } else if (identical(code, $BACKSLASH)) {
         buffer.add(r'\\');
       } else {
-        if (code > 0xffff) {
-          compiler.reportError(
-              diagnosticNode,
-              'Unhandled non-BMP character: U+${code.toRadixString(16)}');
-        }
-        // TODO(lrn): Consider whether all codes above 0x7f really need to
-        // be escaped. We build a Dart string here, so it should be a literal
-        // stage that converts it to, e.g., UTF-8 for a JS interpreter.
         if (code < 0x20) {
-          buffer.add(r'\x');
-          if (code < 0x10) buffer.add('0');
-          buffer.add(code.toRadixString(16));
+          addHexEscape(buffer, code);
         } else if (code >= 0x80) {
-          if (code < 0x100) {
-            buffer.add(r'\x');
+          // TODO(lrn): Consider whether all codes above 0x7f really need to
+          // be escaped. We build a Dart string here, so it should be a literal
+          // stage that converts it to, e.g., UTF-8 for a JS interpreter.
+          if (code >= 0x10000) {

[floitsch, 2012/11/08 15:28:21]

Why not move the surrogate-code into addHexEscape?

[erikcorry, 2012/11/15 13:28:25]

This part has all been rewritten with the new JSON outputting code.

+            // Surrogate pair.
+            addHexEscape(buffer, 0xd800 + (((code - 0x10000) >> 10) & 0x3ff));
+            addHexEscape(buffer, 0xdc00 + (code & 0x3ff));
           } else {
-            buffer.add(r'\u');
-            if (code < 0x1000) {
-              buffer.add('0');
-            }
+            addHexEscape(buffer, code);
           }
-          buffer.add(code.toRadixString(16));
         } else {
           buffer.addCharCode(code);
         }
       }
     }
   }
 
   void visitString(StringConstant constant) {
     buffer.add("'");
     writeEscapedString(constant.value, buffer, constant.node);
@@ skipping 100 matching lines @@
       buffer.add(getJsConstructor(constant.type.element));
       buffer.add("(");
       for (int i = 0; i < constant.fields.length; i++) {
         if (i != 0) buffer.add(", ");
         _visit(constant.fields[i]);
       }
       buffer.add(")");
     }
   }
 }