Avoid crashing on function syntax.

pkg/front_end/lib/src/fasta/source/outline_builder.dart

 // Copyright (c) 2016, 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.
 
 library fasta.outline_builder;
 
 import 'package:kernel/ast.dart' show AsyncMarker, ProcedureKind;
 
 import '../parser/parser.dart' show FormalParameterType, optional;
 
@@ skipping 464 matching lines @@
     library.addEnum(metadata, name, constants, enumKeyword.charOffset);
     checkEmpty(enumKeyword.charOffset);
   }
 
   @override
   void beginFunctionTypeAlias(Token token) {
     library.beginNestedDeclaration(null, hasMembers: false);
   }
 
   @override
+  void handleFunctionType(Token functionToken, Token endToken) {
+    debugEvent("FunctionType");
+    List<FormalParameterBuilder> formals = pop();
+    List<TypeVariableBuilder> typeVariables = pop();
+    TypeBuilder returnType = pop();
+    push(library.addFunctionType(
+        returnType, typeVariables, formals, functionToken.charOffset));
+  }
+
+  @override
   void endFunctionTypeAlias(
       Token typedefKeyword, Token equals, Token endToken) {
     debugEvent("endFunctionTypeAlias");
-    List<FormalParameterBuilder> formals = pop();
-    List<TypeVariableBuilder> typeVariables = pop();
-    String name = pop();
-    TypeBuilder returnType = pop();
+    List<FormalParameterBuilder> formals;
+    List<TypeVariableBuilder> typeVariables;
+    String name;
+    TypeBuilder returnType;
+    if (equals == null) {
+      formals = pop();
+      typeVariables = pop();
+      name = pop();
+      returnType = pop();
+    } else {
+      var type = pop();
+      typeVariables = pop();
+      name = pop();
+      if (type is FunctionTypeBuilder) {
+        // TODO(ahe): We need to start a nested declaration when parsing the
+        // formals and return type so we can correctly bind
+        // `type.typeVariables`. A typedef can have type variables, and a new
+        // function type can also have type variables (representing the type of
+        // a generic function).
+        formals = type.formals;
+        returnType = type.returnType;
+      } else {
+        // TODO(ahe): Improve this error message.
+        library.addCompileTimeError(
+            equals.charOffset, "Can't create typedef from non-function type.");
+      }
+    }
     List<MetadataBuilder> metadata = pop();
     library.addFunctionTypeAlias(metadata, returnType, name, typeVariables,
         formals, typedefKeyword.charOffset);
     checkEmpty(typedefKeyword.charOffset);
   }
 
   @override
   void endTopLevelFields(int count, Token beginToken, Token endToken) {
     debugEvent("endTopLevelFields");
     List<String> names = popList(count);
@@ skipping 139 matching lines @@
   Link<Token> handleMemberName(Link<Token> identifiers) {
     if (!isDartLibrary || identifiers.isEmpty) return identifiers;
     return removeNativeClause(identifiers);
   }
 
   @override
   void debugEvent(String name) {
     // printEvent(name);
   }
 }