Add FunctionType.getNamedParameter.

pkg/kernel/lib/ast.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.
 
 /// -----------------------------------------------------------------------
 ///                           ERROR HANDLING
 /// -----------------------------------------------------------------------
 ///
 /// As a rule of thumb, errors that can be detected statically are handled by
 /// the frontend, typically by translating the erroneous code into a 'throw' or
@@ skipping 3973 matching lines @@
   ///
   /// Any uses of its type parameters become free variables in the returned
   /// type.
   FunctionType get withoutTypeParameters {
     if (typeParameters.isEmpty) return this;
     return new FunctionType(positionalParameters, returnType,
         requiredParameterCount: requiredParameterCount,
         namedParameters: namedParameters);
   }
 
+  /// Looks up the type of the named parameter with the given name.
+  ///
+  /// Returns `null` if there is no named parameter with the given name.
+  DartType getNamedParameter(String name) {
+    int lower = 0;
+    int upper = namedParameters.length - 1;
+    while (lower <= upper) {
+      int pivot = (lower + upper) ~/ 2;
+      int comparison = name.compareTo(namedParameters[pivot].name);

[scheglov, 2017/05/10 18:03:35]

It should be slightly faster to extract `namedParameters[pivot]` into a local
variable and reuse when we found the name.

[Paul Berry, 2017/05/10 18:16:08]

Done.

+      if (comparison == 0) {
+        return namedParameters[pivot].type;
+      } else if (comparison < 0) {
+        upper = pivot - 1;
+      } else {
+        lower = pivot + 1;
+      }
+    }
+    return null;
+  }
+
   int get hashCode => _hashCode ??= _computeHashCode();
 
   int _computeHashCode() {
     int hash = 1237;
     hash = 0x3fffffff & (hash * 31 + requiredParameterCount);
     for (int i = 0; i < typeParameters.length; ++i) {
       TypeParameter parameter = typeParameters[i];
       _temporaryHashCodeTable[parameter] = _temporaryHashCodeTable.length;
       hash = 0x3fffffff & (hash * 31 + parameter.bound.hashCode);
     }
@@ skipping 476 matching lines @@
 /// typedef has not been assigned a canonical name yet.
 ///
 /// Returns `null` if the typedef is `null`.
 CanonicalName getCanonicalNameOfTypedef(Typedef typedef_) {
   if (typedef_ == null) return null;
   if (typedef_.canonicalName == null) {
     throw '$typedef_ has no canonical name';
   }
   return typedef_.canonicalName;
 }