Check default parameters properly

[email protected]

Review URL: https://chromereviews.googleplex.com/155367013

Author: vsmenon

pkg/dev_compiler/lib/src/checker/checker.dart

@@ -504,6 +504,32 @@ class CodeChecker extends RecursiveAstVisitor {
     node.visitChildren(this);
   }
 
+  visitDefaultFormalParameter(DefaultFormalParameter node) {
+    // Check that defaults have the proper subtype.
+    var parameter = node.parameter;
+    var parameterType = _rules.elementType(parameter.element);
+    assert(parameterType != null);
+    var defaultValue = node.defaultValue;
+    var defaultType;
+    if (defaultValue == null) {
+      // TODO(vsm): Should this be null?
+      defaultType = _rules.provider.bottomType;
+    } else {
+      defaultType = _rules.getStaticType(defaultValue);
+    }
+
+    // If defaultType is bottom, this enforces that parameterType is not
+    // non-nullable.
+    if (!_rules.isSubTypeOf(defaultType, parameterType)) {
+      var staticInfo = (defaultValue == null)
+          ? new InvalidVariableDeclaration(
+              _rules, node.identifier, parameterType)
+          : new StaticTypeError(_rules, defaultValue, parameterType);
+      _recordMessage(staticInfo);
+    }
+    node.visitChildren(this);
+  }
+
   visitVariableDeclarationList(VariableDeclarationList node) {
     TypeName type = node.type;
     if (type == null) {

pkg/dev_compiler/lib/src/info.dart

@@ -361,7 +361,7 @@ class InvalidVariableDeclaration extends StaticError {
   final DartType expectedType;
 
   InvalidVariableDeclaration(
-      TypeRules rules, VariableDeclaration declaration, this.expectedType)
+      TypeRules rules, AstNode declaration, this.expectedType)
       : super(declaration);
 
   String get message => 'Type check failed: null is not of type $expectedType';

pkg/dev_compiler/test/checker/checker_test.dart

@@ -46,6 +46,12 @@ main() {
           static num z;
         }
 
+        void foo(int w, [int x = /*severe:StaticTypeError*/null, int /*severe:InvalidVariableDeclaration*/y, int z = 0]) {
+        }
+
+        void bar(int w, {int x = /*severe:StaticTypeError*/null, int /*severe:InvalidVariableDeclaration*/y, int z: 0}) {
+        }
+
         void main() {
           int /*severe:InvalidVariableDeclaration*/x;
           double /*severe:InvalidVariableDeclaration*/y;
@@ -96,6 +102,9 @@ main() {
             // Transformed to: T z = cast(null, T)
             T /*severe:InvalidVariableDeclaration*/z;
           }
+
+          void baz(T x, [T /*severe:InvalidVariableDeclaration*/y, T z = /*severe:StaticTypeError*/null]) {
+          }
         }
 
         class B<T extends List> {

pkg/dev_compiler/test/codegen/expect/methods.txt

@@ -1,4 +1,10 @@
 // Messages from compiling methods.dart
+info: line 10, column 21 of test/codegen/methods.dart: b (num) will need runtime check to cast to type int
+  int z([num b]) => b;
+                    ^
+info: line 15, column 12 of test/codegen/methods.dart: a + b (num) will need runtime check to cast to type int
+    return a + b;
+           ^^^^^
 warning: line 45, column 3 of test/codegen/methods.dart: f.bar("Bar's call method!") requires dynamic invoke
   f.bar("Bar's call method!");
   ^^^^^^^^^^^^^^^^^^^^^^^^^^^

pkg/dev_compiler/test/codegen/expect/methods/methods.js

@@ -12,15 +12,15 @@ var methods;
     }
     z(b) {
       if (b === undefined) b = null;
-      return b
+      return dart.notNull(b)
     }
     zz(b) {
       if (b === undefined) b = 0;
       return b
     }
     w(a, opt$) {
       let b = opt$.b === undefined ? null : opt$.b;
-      return a + b;
+      return dart.notNull(a + b);
     }
     ww(a, opt$) {
       let b = opt$.b === undefined ? 0 : opt$.b;

pkg/dev_compiler/test/codegen/methods.dart

@@ -7,11 +7,11 @@ class A {
     return a;
   }
 
-  int z([int b]) => b;
+  int z([num b]) => b;
 
   int zz([int b = 0]) => b;
 
-  int w(int a, {int b}) {
+  int w(int a, {num b}) {
     return a + b;
   }