Bug 1064493: Better wording for globals validation errors in asm.js; r=luke

js/src/asmjs/AsmJSValidate.cpp

@@ -3588,8 +3588,13 @@ CheckGlobalDotImport(ModuleCompiler &m, PropertyName *varName, ParseNode *initNo
         ParseNode *global = DotBase(base);
         PropertyName *mathOrSimd = DotMember(base);
 
-        if (!IsUseOfName(global, m.module().globalArgumentName()))
+        if (!IsUseOfName(global, m.module().globalArgumentName())) {
+            if (global->isKind(PNK_DOT)) {
+                return m.failName(base, "imports can have at most two dot accesses "
+                                        "(e.g. %s.Math.sin)", m.module().globalArgumentName());
+            }
             return m.failName(base, "expecting %s.*", m.module().globalArgumentName());
+        }
 
         if (mathOrSimd == m.cx()->names().Math)
             return CheckGlobalMathImport(m, initNode, varName, field);