add special case for min/max, fixes #281

lib/src/checker/resolver.dart

 // Copyright (c) 2015, 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.
 
 /// Encapsulates how to invoke the analyzer resolver and overrides how it
 /// computes types on expressions to use our restricted set of types.
 library dev_compiler.src.checker.resolver;
 
 import 'package:analyzer/analyzer.dart';
 import 'package:analyzer/src/generated/ast.dart';
@@ skipping 619 matching lines @@
         } else {
           var coreLib = _typeProvider.objectType.element.library;
           var classElem = coreLib.getType(typeStr);
           if (classElem != null) {
             var type = fillDynamicTypeArgs(classElem.type, _typeProvider);
             node.staticType = type;
           }
         }
       }
     }
+
+    // Pretend dart:math's min and max are generic:
+    //
+    //     T min<T extends num>(T x, T y);
+    //
+    // and infer T. In practice, this just means if the type of x and y are
+    // both double or both int, we treat that as the return type.
+    //
+    // The Dart spec has similar treatment for binary operations on numbers.
+    //
+    // TODO(jmesserly): remove this when we have a fix for
+    // https://github.com/dart-lang/dev_compiler/issues/28
+    if (isDartMathMinMax(e)) {
+      var args = node.argumentList.arguments;
+      if (args.length == 2) {
+        var tx = args[0].staticType;
+        var ty = args[1].staticType;
+        if (tx == ty &&
+            (tx == _typeProvider.intType || tx == _typeProvider.doubleType)) {
+          node.staticType = tx;
+        }
+      }
+    }
   }
 
   void _inferObjectAccess(
       Expression node, Expression target, SimpleIdentifier id) {
     // Search for Object accesses.
     var name = id.name;
     if (node.staticType.isDynamic &&
         _objectMembers.containsKey(name) &&
         isDynamicTarget(target)) {
       target.staticType = _typeProvider.objectType;
@@ skipping 40 matching lines @@
     }
   }
 
   // Review note: no longer need to override visitFunctionExpression, this is
   // handled by the analyzer internally.
   // TODO(vsm): in visitbinaryExpression: check computeStaticReturnType result?
   // TODO(vsm): in visitFunctionDeclaration: Should we ever use the expression
   // type in a (...) => expr or just the written type?
 
 }