Problems reported:

parser/patterns/patternVariableDeclaration_inClass:2:7: A pattern variable declaration may not appear outside a function or method.
  var (a, b) = (0, 1);
      ^^^^^^

beginCompilationUnit(class)
  beginMetadataStar(class)
  endMetadataStar(0)
  beginClassOrMixinOrNamedMixinApplicationPrelude(class)
    handleIdentifier(C, classOrMixinDeclaration)
    handleNoTypeVariables({)
    beginClassDeclaration(class, null, null, null, null, null, null, null, null, C)
      handleNoPrimaryConstructor(C, null, false)
      handleNoType(C)
      handleClassExtends(null, 1)
      handleClassNoWithClause()
      handleImplements(null, 0)
      handleClassHeader(class, class, null)
      beginClassOrMixinOrExtensionBody(DeclarationKind.Class, {)
        beginMetadataStar(var)
        endMetadataStar(0)
        beginMember()
          handleRecoverableError(PatternVariableDeclarationOutsideFunctionOrMethod, (, ))
          beginFields(DeclarationKind.Class, null, null, null, null, null, null, var, {)
            handleNoType(var)
            handleIdentifier(, fieldDeclaration)
            beginFieldInitializer(=)
              beginParenthesizedExpressionOrRecordLiteral(()
                handleLiteralInt(0)
                handlePositionalRecordField(0)
                handleLiteralInt(1)
                handlePositionalRecordField(1)
              endRecordLiteral((, 2, null)
            endFieldInitializer(=, ))
          endFields(DeclarationKind.Class, null, null, null, null, null, null, var, 1, var, ;)
        endMember()
      endClassOrMixinOrExtensionBody(DeclarationKind.Class, 1, {, })
    endClassDeclaration(class, })
  endTopLevelDeclaration(})
endCompilationUnit(1, )