[dart2wasm] Implement constant symbols.

Change-Id: I758576a7a35c6ffe127fd02eb394e97719750476
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/250776
Reviewed-by: Aske Simon Christensen <askesc@google.com>
Commit-Queue: Joshua Litt <joshualitt@google.com>

pkg/dart2wasm/lib/constants.dart

@@ -826,4 +826,20 @@ class ConstantCreator extends ConstantVisitor<ConstantInfo?> {
       });
     }
   }
+
+  @override
+  ConstantInfo? visitSymbolConstant(SymbolConstant constant) {
+    ClassInfo info = translator.classInfo[translator.symbolClass]!;
+    translator.functions.allocateClass(info.classId);
+    w.RefType stringType =
+        translator.classInfo[translator.coreTypes.stringClass]!.nonNullableType;
+    StringConstant nameConstant = StringConstant(constant.name);
+    ensureConstant(nameConstant);
+    return createConstant(constant, info.nonNullableType, (function, b) {
+      b.i32_const(info.classId);
+      b.i32_const(initialIdentityHash);
+      constants.instantiateConstant(function, b, nameConstant, stringType);
+      translator.struct_new(b, info);
+    });
+  }
 }

pkg/dart2wasm/lib/translator.dart

@@ -112,6 +112,7 @@ class Translator {
   late final Class byteDataViewClass;
   late final Class typeErrorClass;
   late final Class typeUniverseClass;
+  late final Class symbolClass;
   late final Procedure wasmFunctionCall;
   late final Procedure wasmTableCallIndirect;
   late final Procedure stackTraceCurrent;
@@ -188,6 +189,7 @@ class Translator {
     Class Function(String) lookupCore = makeLookup("dart.core");
     Class Function(String) lookupCollection = makeLookup("dart.collection");
     Class Function(String) lookupFfi = makeLookup("dart.ffi");
+    Class Function(String) lookupInternal = makeLookup("dart._internal");
     Class Function(String) lookupTypedData = makeLookup("dart.typed_data");
     Class Function(String) lookupWasm = makeLookup("dart.wasm");
 
@@ -235,6 +237,7 @@ class Translator {
     typedListClass = lookupTypedData("_TypedList");
     typedListViewClass = lookupTypedData("_TypedListView");
     byteDataViewClass = lookupTypedData("_ByteDataView");
+    symbolClass = lookupInternal("Symbol");
     wasmFunctionCall =
         wasmFunctionClass.procedures.firstWhere((p) => p.name.text == "call");
     wasmTableCallIndirect = wasmTableClass.procedures

sdk/lib/_internal/wasm/lib/symbol_patch.dart

@@ -0,0 +1,68 @@
+// Copyright (c) 2022, 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 "internal_patch.dart";
+
+// TODO(49531): This file is nearly identical to the VM's
+// symbol_patch.dart, with the exception of the added pragma on `const Symbol`.
+// Unfortunately, adding this pragma to the VM's symbol_patch causes a
+// deadlock. When this bug is fixed we can share a patch file with the VM.
+
+@patch
+class Symbol {
+  // TODO(http://dartbug.com/46716): Recognize Symbol in the VM.
+  @patch
+  @pragma("wasm:entry-point")
+  const Symbol(String name) : this._name = name;
+
+  @patch
+  String toString() => 'Symbol("${computeUnmangledName(this)}")';
+
+  @patch
+  static String computeUnmangledName(Symbol symbol) {
+    String string = Symbol.getName(symbol);
+
+    // get:foo -> foo
+    // set:foo -> foo=
+    // get:_foo@xxx -> _foo
+    // set:_foo@xxx -> _foo=
+    // Class._constructor@xxx -> Class._constructor
+    // _Class@xxx._constructor@xxx -> _Class._constructor
+    // lib._S@xxx with lib._M1@xxx, lib._M2@xxx -> lib._S with lib._M1, lib._M2
+    StringBuffer result = new StringBuffer();
+    bool add_setter_suffix = false;
+    var pos = 0;
+    if (string.length >= 4 && string[3] == ':') {
+      // Drop 'get:' or 'set:' prefix.
+      pos = 4;
+      if (string[0] == 's') {
+        add_setter_suffix = true;
+      }
+    }
+    // Skip everything between AT and PERIOD, SPACE, COMMA or END
+    bool skip = false;
+    for (; pos < string.length; pos++) {
+      var char = string[pos];
+      if (char == '@') {
+        skip = true;
+      } else if (char == '.' || char == ' ' || char == ',') {
+        skip = false;
+      }
+      if (!skip) {
+        result.write(char);
+      }
+    }
+    if (add_setter_suffix) {
+      result.write('=');
+    }
+    return result.toString();
+  }
+
+  // Must be kept in sync with Symbol::CanonicalizeHash in object.cc.
+  @patch
+  int get hashCode {
+    const arbitraryPrime = 664597;
+    return 0x1fffffff & (arbitraryPrime * _name.hashCode);
+  }
+}

sdk/lib/libraries.json

@@ -168,7 +168,7 @@
           "_internal/wasm/lib/class_id.dart",
           "_internal/wasm/lib/patch.dart",
           "_internal/wasm/lib/print_patch.dart",
-          "_internal/vm/lib/symbol_patch.dart"
+          "_internal/wasm/lib/symbol_patch.dart"
         ]
       },
       "_js_helper": {

sdk/lib/libraries.yaml

@@ -165,7 +165,7 @@ wasm:
       - _internal/wasm/lib/class_id.dart
       - _internal/wasm/lib/patch.dart
       - _internal/wasm/lib/print_patch.dart
-      - _internal/vm/lib/symbol_patch.dart
+      - _internal/wasm/lib/symbol_patch.dart
     _js_helper:
       uri: _internal/wasm/lib/js_helper.dart
     async: