Use different SDKs based on option settings

pkg/analyzer/lib/src/generated/engine.dart

Index: pkg/analyzer/lib/src/generated/engine.dart
diff --git a/pkg/analyzer/lib/src/generated/engine.dart b/pkg/analyzer/lib/src/generated/engine.dart
index b27c42e927430d138f919ebf01c0b0d60f4ddfb9..2e1d9f051b1ad42b8e3188cea76989e95dbba4e8 100644
--- a/pkg/analyzer/lib/src/generated/engine.dart
+++ b/pkg/analyzer/lib/src/generated/engine.dart
@@ -1123,6 +1123,19 @@ abstract class AnalysisOptions {
    * Return `true` if strong mode analysis should be used.
    */
   bool get strongMode;
+
+  /**
+   * Return an integer encoding of the values of the options that need to be the
+   * same across all of the contexts associated with partitions that are to be
+   * shared by a single analysis context.
+   */
+  int encodeCrossContextOptions();
+
+  /**
+   * Set the values of the cross-context options to match those in the given set
+   * of [options].
+   */
+  void setCrossContextOptionsFrom(AnalysisOptions options);
 }
 
 /**
@@ -1135,6 +1148,14 @@ class AnalysisOptionsImpl implements AnalysisOptions {
    */
   static const int DEFAULT_CACHE_SIZE = 64;
 
+  static const int ENABLE_ASSERT_FLAG = 0x01;
+  static const int ENABLE_ASYNC_FLAG = 0x02;
+  static const int ENABLE_GENERIC_METHODS_FLAG = 0x04;
+  static const int ENABLE_STRICT_CALL_CHECKS_FLAG = 0x08;
+  static const int ENABLE_STRONG_MODE_FLAG = 0x10;
+  static const int ENABLE_STRONG_MODE_HINTS_FLAG = 0x20;
+  static const int ENABLE_SUPER_MIXINS_FLAG = 0x40;
+
   /**
    * A predicate indicating whether analysis is to parse and analyze function
    * bodies.
@@ -1308,6 +1329,29 @@ class AnalysisOptionsImpl implements AnalysisOptions {
     _analyzeFunctionBodiesPredicate = value;
   }
 
+  @override
+  int encodeCrossContextOptions() =>
+      (enableAssertMessage ? ENABLE_ASSERT_FLAG : 0) |
+      (enableAsync ? ENABLE_ASYNC_FLAG : 0) |
+      (enableGenericMethods ? ENABLE_GENERIC_METHODS_FLAG : 0) |
+      (enableStrictCallChecks ? ENABLE_STRICT_CALL_CHECKS_FLAG : 0) |
+      (strongMode ? ENABLE_STRONG_MODE_FLAG : 0) |
+      (strongModeHints ? ENABLE_STRONG_MODE_HINTS_FLAG : 0) |
+      (enableSuperMixins ? ENABLE_SUPER_MIXINS_FLAG : 0);
+
+  @override
+  void setCrossContextOptionsFrom(AnalysisOptions options) {
+    enableAssertMessage = options.enableAssertMessage;
+    enableAsync = options.enableAsync;
+    enableGenericMethods = options.enableGenericMethods;
+    enableStrictCallChecks = options.enableStrictCallChecks;
+    enableSuperMixins = options.enableSuperMixins;
+    strongMode = options.strongMode;
+    if (options is AnalysisOptionsImpl) {
+      strongModeHints = options.strongModeHints;
+    }
+  }
+
   /**
    * Predicate used for [analyzeFunctionBodiesPredicate] when
    * [analyzeFunctionBodies] is set to `true`.