fix #25573, add option to disable implicit dynamic

R=leafp@google.com

Review URL: https://codereview.chromium.org/2093523002 .

pkg/analyzer/lib/src/context/context.dart

@@ -281,6 +281,9 @@ class AnalysisContextImpl implements InternalAnalysisContext {
         ((options is AnalysisOptionsImpl)
             ? this._options.implicitCasts != options.implicitCasts
             : false) ||
+        ((options is AnalysisOptionsImpl)
+            ? this._options.implicitDynamic != options.implicitDynamic
+            : false) ||
         this._options.enableStrictCallChecks !=
             options.enableStrictCallChecks ||
         this._options.enableGenericMethods != options.enableGenericMethods ||
@@ -313,6 +316,7 @@ class AnalysisContextImpl implements InternalAnalysisContext {
     if (options is AnalysisOptionsImpl) {
       this._options.strongModeHints = options.strongModeHints;
       this._options.implicitCasts = options.implicitCasts;
+      this._options.implicitDynamic = options.implicitDynamic;
     }
     if (needsRecompute) {
       for (WorkManager workManager in workManagers) {

pkg/analyzer/lib/src/dart/element/type.dart

@@ -926,6 +926,39 @@ class FunctionTypeImpl extends TypeImpl implements FunctionType {
     }
   }
 
+  /**
+   * Given a generic function type [g] and an instantiated function type [f],
+   * find a list of type arguments TArgs such that `g<TArgs> == f`,
+   * and return TArgs.
+   *
+   * This function must be called with type [f] that was instantiated from [g].
+   */
+  static Iterable<DartType> recoverTypeArguments(
+      FunctionType g, FunctionType f) {
+    // TODO(jmesserly): perhaps a better design here would be: instead of
+    // recording staticInvokeType on InvocationExpression, we could record the
+    // instantiated type arguments, that way we wouldn't need to recover them.
+    //
+    // For now though, this is a pretty quick operation.
+    assert(identical(g.element, f.element));
+    assert(g.typeFormals.isNotEmpty && f.typeFormals.isEmpty);
+    assert(g.typeFormals.length + g.typeArguments.length ==
+        f.typeArguments.length);
+
+    // Instantiation in Analyzer works like this:
+    // Given:
+    //     {U/T} <S> T -> S
+    // Where {U/T} represents the typeArguments (U) and typeParameters (T) list,
+    // and <S> represents the typeFormals.
+    //
+    // Now instantiate([V]), and the result should be:
+    //     {U/T, V/S} T -> S.
+    //
+    // Therefore, we can recover the typeArguments from our instantiated
+    // function.
+    return f.typeArguments.skip(g.typeArguments.length);
+  }
+
   /**
    * Compares two function types [t] and [s] to see if their corresponding
    * parameter types match [parameterRelation] and their return types match

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

@@ -1314,6 +1314,18 @@ class AnalysisOptionsImpl implements AnalysisOptions {
   @override
   bool finerGrainedInvalidation = false;
 
+  /**
+   * A flag indicating whether implicit dynamic type is allowed, on by default.
+   *
+   * This flag can be used without necessarily enabling [strongMode], but it is
+   * designed with strong mode's type inference in mind. Without type inference,
+   * it will raise many errors. Also it does not provide type safety without
+   * strong mode.
+   *
+   * This option is experimental and subject to change.
+   */
+  bool implicitDynamic = true;
+
   /**
    * Initialize a newly created set of analysis options to have their default
    * values.
@@ -1346,6 +1358,7 @@ class AnalysisOptionsImpl implements AnalysisOptions {
     if (options is AnalysisOptionsImpl) {
       strongModeHints = options.strongModeHints;
       implicitCasts = options.implicitCasts;
+      implicitDynamic = options.implicitDynamic;
     }
     trackCacheDependencies = options.trackCacheDependencies;
     finerGrainedInvalidation = options.finerGrainedInvalidation;

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

@@ -2859,6 +2859,16 @@ abstract class ErrorCode {
     StrongModeCode.DOWN_CAST_IMPLICIT,
     StrongModeCode.DYNAMIC_CAST,
     StrongModeCode.DYNAMIC_INVOKE,
+    StrongModeCode.IMPLICIT_DYNAMIC_FIELD,
+    StrongModeCode.IMPLICIT_DYNAMIC_FUNCTION,
+    StrongModeCode.IMPLICIT_DYNAMIC_INVOKE,
+    StrongModeCode.IMPLICIT_DYNAMIC_LIST_LITERAL,
+    StrongModeCode.IMPLICIT_DYNAMIC_MAP_LITERAL,
+    StrongModeCode.IMPLICIT_DYNAMIC_METHOD,
+    StrongModeCode.IMPLICIT_DYNAMIC_PARAMETER,
+    StrongModeCode.IMPLICIT_DYNAMIC_RETURN,
+    StrongModeCode.IMPLICIT_DYNAMIC_TYPE,
+    StrongModeCode.IMPLICIT_DYNAMIC_VARIABLE,
     StrongModeCode.INFERRED_TYPE,
     StrongModeCode.INFERRED_TYPE_ALLOCATION,
     StrongModeCode.INFERRED_TYPE_CLOSURE,
@@ -5874,6 +5884,17 @@ class StrongModeCode extends ErrorCode {
       'The type of {0}.{1} ({2}) is not a '
       'subtype of {3}.{1} ({4}).';
 
+  /**
+   * This is appended to the end of an error message about implicit dynamic.
+   *
+   * The idea is to make sure the user is aware that this error message is the
+   * result of turning on a particular option, and they are free to turn it
+   * back off.
+   */
+  static const String _implicitDynamicTip =
+      ". Either add an explicit type like 'dynamic'"
+      ", or enable implicit-dynamic in your Analyzer options.";
+
   static const String _inferredTypeMessage = '{0} has inferred type {1}';
 
   static const StrongModeCode DOWN_CAST_COMPOSITE = const StrongModeCode(
@@ -5947,6 +5968,63 @@ class StrongModeCode extends ErrorCode {
       'Field declaration {3}.{1} cannot be '
       'overridden in {0}.');
 
+  static const StrongModeCode IMPLICIT_DYNAMIC_PARAMETER = const StrongModeCode(
+      ErrorType.COMPILE_TIME_ERROR,
+      'IMPLICIT_DYNAMIC_PARAMETER',
+      "Missing parameter type for '{0}'$_implicitDynamicTip");
+
+  static const StrongModeCode IMPLICIT_DYNAMIC_RETURN = const StrongModeCode(
+      ErrorType.COMPILE_TIME_ERROR,
+      'IMPLICIT_DYNAMIC_RETURN',
+      "Missing return type for '{0}'$_implicitDynamicTip");
+
+  static const StrongModeCode IMPLICIT_DYNAMIC_VARIABLE = const StrongModeCode(
+      ErrorType.COMPILE_TIME_ERROR,
+      'IMPLICIT_DYNAMIC_VARIABLE',
+      "Missing variable type for '{0}'$_implicitDynamicTip");
+
+  static const StrongModeCode IMPLICIT_DYNAMIC_FIELD = const StrongModeCode(
+      ErrorType.COMPILE_TIME_ERROR,
+      'IMPLICIT_DYNAMIC_FIELD',
+      "Missing field type for '{0}'$_implicitDynamicTip");
+
+  static const StrongModeCode IMPLICIT_DYNAMIC_TYPE =
+      const StrongModeCode(
+          ErrorType.COMPILE_TIME_ERROR,
+          'IMPLICIT_DYNAMIC_TYPE',
+          "Missing type arguments for generic type '{0}'"
+          "$_implicitDynamicTip");
+
+  static const StrongModeCode IMPLICIT_DYNAMIC_LIST_LITERAL =
+      const StrongModeCode(
+          ErrorType.COMPILE_TIME_ERROR,
+          'IMPLICIT_DYNAMIC_LIST_LITERAL',
+          "Missing type argument for list literal$_implicitDynamicTip");
+
+  static const StrongModeCode IMPLICIT_DYNAMIC_MAP_LITERAL =
+      const StrongModeCode(
+          ErrorType.COMPILE_TIME_ERROR,
+          'IMPLICIT_DYNAMIC_MAP_LITERAL',
+          'Missing type arguments for map literal$_implicitDynamicTip');
+
+  static const StrongModeCode IMPLICIT_DYNAMIC_FUNCTION = const StrongModeCode(
+      ErrorType.COMPILE_TIME_ERROR,
+      'IMPLICIT_DYNAMIC_FUNCTION',
+      "Missing type arguments for generic function '{0}<{1}>'"
+      "$_implicitDynamicTip");
+
+  static const StrongModeCode IMPLICIT_DYNAMIC_METHOD = const StrongModeCode(
+      ErrorType.COMPILE_TIME_ERROR,
+      'IMPLICIT_DYNAMIC_METHOD',
+      "Missing type arguments for generic method '{0}<{1}>'"
+      "$_implicitDynamicTip");
+
+  static const StrongModeCode IMPLICIT_DYNAMIC_INVOKE = const StrongModeCode(
+      ErrorType.COMPILE_TIME_ERROR,
+      'IMPLICIT_DYNAMIC_INVOKE',
+      "Missing type arguments for calling generic function type '{0}'"
+          "$_implicitDynamicTip");
+
   @override
   final ErrorType type;