implement notNull checking for num -> int and num -> double

[email protected]

Review URL: https://chromereviews.googleplex.com/144347013

Author: John Messerly

lib/runtime/dart_runtime.js

@@ -86,6 +86,13 @@ var dart;
   }
   dart.equals = equals;
 
+  /** Checks that `x` is not null or undefined. */
+  function notNull(x) {
+    if (x == null) throw 'expected not-null value';
+    return x;
+  }
+  dart.notNull = notNull;
+
   /**
    * Defines a lazy property.
    * After initial get or set, it will replace itself with a value property.

lib/src/checker/rules.dart

@@ -25,7 +25,7 @@ abstract class TypeRules {
   bool isBoolType(DartType t) => t == provider.boolType;
   bool isDoubleType(DartType t) => t == provider.doubleType;
   bool isIntType(DartType t) => t == provider.intType;
-  bool isNumType(DartType t) => t.name == "num";
+  bool isNumType(DartType t) => t == provider.intType.superclass;
 
   StaticInfo checkAssignment(Expression expr, DartType t);
 

lib/src/codegen/js_codegen.dart

@@ -95,6 +95,21 @@ var $_libraryName;
   /// Conversions that we don't handle end up here.
   @override
   void visitConversion(Conversion node) {
+    var from = node.baseType, to = node.convertedType;
+
+    // num to int or num to double is just a null check.
+    if (rules.isNumType(from) &&
+        (rules.isIntType(to) || rules.isDoubleType(to))) {
+      // TODO(jmesserly): a lot of these checks are meaningless, as people use
+      // `num` to mean "any kind of number" rather than "could be null".
+      // The core libraries especially suffer from this problem, with many of
+      // the `num` methods returning `num`.
+      out.write('dart.notNull(');
+      node.expression.accept(this);
+      out.write(')');
+      return;
+    }
+
     out.write('/* Unimplemented: ');
     out.write('${node.description}');
     out.write(' */ ');

test/codegen/expect/core/core.js

@@ -367,9 +367,9 @@ var core;
       /* Unimplemented FunctionDeclarationStatement: String sixDigits(int n) {if (n >= 100000) return "$n"; if (n >= 10000) return "0$n"; if (n >= 1000) return "00$n"; if (n >= 100) return "000$n"; if (n >= 10) return "0000$n"; return "00000$n";} *//* Unimplemented FunctionDeclarationStatement: String twoDigits(int n) {if (n >= 10) return "$n"; return "0$n";} */if (this.inMicroseconds < 0) {
         return "-" + (/* Unimplemented postfix operator: -this */) + "";
       }
-      let twoDigitMinutes = twoDigits(/* Unimplemented: DownCast: num to int */ this.inMinutes.remainder(MINUTES_PER_HOUR));
-      let twoDigitSeconds = twoDigits(/* Unimplemented: DownCast: num to int */ this.inSeconds.remainder(SECONDS_PER_MINUTE));
-      let sixDigitUs = sixDigits(/* Unimplemented: DownCast: num to int */ this.inMicroseconds.remainder(MICROSECONDS_PER_SECOND));
+      let twoDigitMinutes = twoDigits(dart.notNull(this.inMinutes.remainder(MINUTES_PER_HOUR)));
+      let twoDigitSeconds = twoDigits(dart.notNull(this.inSeconds.remainder(SECONDS_PER_MINUTE)));
+      let sixDigitUs = sixDigits(dart.notNull(this.inMicroseconds.remainder(MICROSECONDS_PER_SECOND)));
       return "" + (this.inHours) + ":" + (twoDigitMinutes) + ":" + (twoDigitSeconds) + "." + (sixDigitUs) + "";
     }
     get isNegative() { return this._duration < 0; }