[strong] Disallow implicit conversions for binary arithmetic operations

src/runtime.js

Index: src/runtime.js
diff --git a/src/runtime.js b/src/runtime.js
index aaaa4fecba110c4e5e3edc0a88ea9f6a3e946e89..a4677da316d1cb28a3c96ce730e0fb1cc5926573 100644
--- a/src/runtime.js
+++ b/src/runtime.js
@@ -199,6 +199,15 @@ function SUB(y) {
 }
 
 
+// ECMA-262, section 11.6.2, page 50.
+function SUB_STRONG(y) {
+  if (IS_NUMBER(this) && IS_NUMBER(y)) {
+    return %NumberSub(this, y);
+  }
+  throw %MakeTypeError('strong_implicit_cast');
+}
+
+
 // ECMA-262, section 11.5.1, page 48.
 function MUL(y) {
   var x = IS_NUMBER(this) ? this : %NonNumberToNumber(this);
@@ -207,6 +216,15 @@ function MUL(y) {
 }
 
 
+// ECMA-262, section 11.5.1, page 48.
+function MUL_STRONG(y) {
+  if (IS_NUMBER(this) && IS_NUMBER(y)) {
+    return %NumberMul(this, y);
+  }
+  throw %MakeTypeError('strong_implicit_cast');
+}
+
+
 // ECMA-262, section 11.5.2, page 49.
 function DIV(y) {
   var x = IS_NUMBER(this) ? this : %NonNumberToNumber(this);
@@ -215,6 +233,15 @@ function DIV(y) {
 }
 
 
+// ECMA-262, section 11.5.2, page 49.
+function DIV_STRONG(y) {
+  if (IS_NUMBER(this) && IS_NUMBER(y)) {
+    return %NumberDiv(this, y);
+  }
+  throw %MakeTypeError('strong_implicit_cast');
+}
+
+
 // ECMA-262, section 11.5.3, page 49.
 function MOD(y) {
   var x = IS_NUMBER(this) ? this : %NonNumberToNumber(this);
@@ -223,6 +250,14 @@ function MOD(y) {
 }
 
 
+// ECMA-262, section 11.5.3, page 49.
+function MOD_STRONG(y) {
+  if (IS_NUMBER(this) && IS_NUMBER(y)) {
+    return %NumberMod(this, y);
+  }
+  throw %MakeTypeError('strong_implicit_cast');
+}
+
 
 /* -------------------------------------------
    - - -   B i t   o p e r a t i o n s   - - -