Merge pull request #2539 from Microsoft/forOfLengthCache

Remove experimental flag to cache for-of length checks.

Author: CyrusNajmabadi

Jakefile

@@ -254,8 +254,6 @@ function compileFile(outFile, sources, prereqs, prefixes, useBuiltCompiler, noOu
             options += " --stripInternal"
         }
 
-        options += " --cacheDownlevelForOfLength";
-
         var cmd = host + " " + dir + compilerFilename + " " + options + " ";
         cmd = cmd + sources.join(" ");
         console.log(cmd + "\n");

src/compiler/commandLineParser.ts

@@ -140,12 +140,6 @@ module ts {
             description: Diagnostics.Do_not_emit_declarations_for_code_that_has_an_internal_annotation,
             experimental: true
         },
-        {
-            name: "cacheDownlevelForOfLength",
-            type: "boolean",
-            description: "Cache length access when downlevel emitting for-of statements",
-            experimental: true,
-        },
         {
             name: "target",
             shortName: "t",

src/compiler/emitter.ts

@@ -2167,8 +2167,6 @@ module ts {
                 let counter = createTempVariable(TempFlags._i);
                 let rhsReference = rhsIsIdentifier ? <Identifier>node.expression : createTempVariable(TempFlags.Auto);
 
-                var cachedLength = compilerOptions.cacheDownlevelForOfLength ? createTempVariable(TempFlags._n) : undefined;
-
                 // This is the let keyword for the counter and rhsReference. The let keyword for
                 // the LHS will be emitted inside the body.
                 emitStart(node.expression);
@@ -2189,28 +2187,15 @@ module ts {
                     emitEnd(node.expression);
                 }
 
-                if (cachedLength) {
-                    write(", ");
-                    emitNodeWithoutSourceMap(cachedLength);
-                    write(" = ");
-                    emitNodeWithoutSourceMap(rhsReference);
-                    write(".length");
-                }
-
                 write("; ");
 
                 // _i < _a.length;
                 emitStart(node.initializer);
                 emitNodeWithoutSourceMap(counter);
                 write(" < ");
 
-                if (cachedLength) {
-                    emitNodeWithoutSourceMap(cachedLength);
-                }
-                else {
-                    emitNodeWithoutSourceMap(rhsReference);
-                    write(".length");
-                }
+                emitNodeWithoutSourceMap(rhsReference);
+                write(".length");
 
                 emitEnd(node.initializer);
                 write("; ");

src/compiler/types.ts

@@ -1588,7 +1588,6 @@ module ts {
         version?: boolean;
         watch?: boolean;
         /* @internal */ stripInternal?: boolean;
-        /* @internal */ cacheDownlevelForOfLength?: boolean;
         [option: string]: string | number | boolean;
     }