[MERGE #3904 @boingoing] Strict mode global lambda functions should u…

…se LdThis instead of StrictLdThis Merge pull request #3904 from boingoing:LdThisForStrictLambda
chakra-core · Oct 9, 2017 · d234b08 · d234b08
2 parents 13e0e02 + d0b6949
commit d234b08
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Showing 2 changed files with 18 additions and 2 deletions.
diff --git a/lib/Runtime/ByteCode/ByteCodeEmitter.cpp b/lib/Runtime/ByteCode/ByteCodeEmitter.cpp
@@ -2376,7 +2376,7 @@ void ByteCodeGenerator::GetEnclosingNonLambdaScope(FuncInfo *funcInfo, Scope * &
 
 void ByteCodeGenerator::EmitThis(FuncInfo *funcInfo, Js::RegSlot fromRegister)
 {
-    if (funcInfo->byteCodeFunction->GetIsStrictMode() && !funcInfo->IsGlobalFunction())
+    if (funcInfo->byteCodeFunction->GetIsStrictMode() && !funcInfo->IsGlobalFunction() && !funcInfo->IsLambda())
     {
         m_writer.Reg2(Js::OpCode::StrictLdThis, funcInfo->GetThisSymbol()->GetLocation(), fromRegister);
     }

diff --git a/test/Basics/SpecialSymbolCapture.js b/test/Basics/SpecialSymbolCapture.js
@@ -867,7 +867,23 @@ var tests = [
             }
             foo('arguments');
         }
-    }
+    },
+    {
+        name: "Global 'this' binding captured by strict-mode arrow",
+        body: function() {
+            WScript.LoadScript(`"use strict";
+                assert.areEqual(this, (() => this)(), "Lambda should load the global 'this' value itself via LdThis (not StrictLdThis)");
+            `);
+
+            WScript.LoadScript(`
+                assert.areEqual(this, (() => { "use strict"; return this; })(), "Lambda which has a 'use strict' clause inside");
+            `);
+
+            WScript.LoadScript(`"use strict";
+                assert.areEqual('object', typeof (() => this)(), "Verify lambda can load global 'this' value even if the global body itself does not have a 'this' binding");
+            `);
+        }
+    },
 ]
 
 testRunner.runTests(tests, { verbose: WScript.Arguments[0] != "summary" });