Generate proper C++ for capture by-reference.

ast/jsonInterfaces.ts

@@ -250,6 +250,8 @@ module TDev.AST.Json
         locals?:JLocalDef[]; // this contains the reference in short mode; it never contains anything else
         isImplicit:boolean;
         isOptional:boolean;
+        allLocals: JLocalDef[];
+        capturedLocals: JLocalDef[];
     }
 
     export interface JOptionalParameter extends JNode
@@ -377,6 +379,7 @@ module TDev.AST.Json
     {
         name:string;
         type:JTypeRef;
+        isByRef: boolean;
     }
 
     // Response to:

embedded/emitter.ts

@@ -88,8 +88,11 @@ module TDev {
 
       public visitExprHolder(env: H.Env, locals: J.JLocalDef[], expr: J.JExprHolder) {
         var decls = locals.map(d => {
-          var x = H.defaultValueForType(this.libraryMap, d.type);
-          return this.visit(env, d) + (x ? " = " + x : "") + ";";
+          // Side-effect: marks [d] as promoted, if needed.
+          var decl = this.visit(env, d);
+          var defaultValue = H.defaultValueForType(this.libraryMap, d.type);
+          var initialValue = !H.isPromoted(env, d.id) && defaultValue ? " = " + defaultValue : "";
+          return decl + initialValue + ";";
         });
         return decls.join("\n"+env.indent) +
           (decls.length ? "\n" + env.indent : "") +
@@ -104,11 +107,23 @@ module TDev {
         //   which C and C++ accept both "f" and "&f" (we hence use the former)
         // - arrays, strings, user-defined objects, which are in fact of type
         //   "ManagedType<T>", no "&" operator here.
-        return H.resolveLocal(env, name, id);
+        // However, we now support capture-by-reference. This means that the
+        // data is ref-counted (so as to be shared), but assignment and
+        // reference operate on the ref-counted data (not on the pointer), so we
+        // must add a dereference there.
+        var prefix = H.isPromoted(env, id) ? "*" : "";
+        return prefix+H.resolveLocal(env, name, id);
       }
 
-      public visitLocalDef(env: H.Env, name: string, id: string, type: J.JTypeRef) {
-        return H.mkType(env, this.libraryMap, type)+" "+H.resolveLocal(env, name, id);
+      public visitLocalDef(env: H.Env, name: string, id: string, type: J.JTypeRef, isByRef: boolean) {
+        var t = H.mkType(env, this.libraryMap, type);
+        var l = H.resolveLocal(env, name, id);
+        if (H.shouldPromoteToRef(env, type, isByRef)) {
+          H.markPromoted(env, id);
+          return "ManagedType<"+ t + "> " + l + "(new "+t+")";
+        } else {
+          return t + " " + l;
+        }
       }
 
       // Allows the target to redefine their own string type.

embedded/helpers.ts

@@ -140,6 +140,10 @@ module TDev {
         libName: string;
 
         indent: string;
+
+        // A table of id's that have been promoted to ref-counted types (because
+        // they were captured by a closure). Modified in an imperative manner.
+        promotedIds: StringMap<boolean>;
       }
 
       export function indent(e: Env): Env {
@@ -149,9 +153,18 @@ module TDev {
           globalNameMap: e.globalNameMap,
           libName: e.libName,
           indent: e.indent + "  ",
+          promotedIds: e.promotedIds,
         };
       }
 
+      export function markPromoted(e: Env, id: string) {
+        e.promotedIds[id] = true;
+      }
+
+      export function isPromoted(e: Env, id: string) {
+        return e.promotedIds[id];
+      }
+
       export function emptyEnv(g: GlobalNameMap, libName: string): Env {
         var usedNames: StringMap<boolean> = {};
         var m = libName ? g.libraries[libName] : g.program;
@@ -165,6 +178,7 @@ module TDev {
           globalNameMap: g,
           libName: libName,
           indent: "",
+          promotedIds: {},
         };
       }
 
@@ -240,6 +254,10 @@ module TDev {
           return n;
       }
 
+      export function shouldPromoteToRef(e: Env, t: J.JTypeRef, isByRef: boolean) {
+        return typeof t == "string" && isByRef;
+      }
+
 
       // --- Helper functions.
       // For constructing / modifying AST nodes.
@@ -325,7 +343,7 @@ module TDev {
         var retType = outParams.length ? mkType(env, libMap, outParams[0].type) : "void";
         var args = "(" + inParams.map(p => mkParam(env, libMap, p)).join(", ") + ")";
         if (isLambda)
-          return "[=] "+args+" -> "+retType;
+          return "[=] "+args+" mutable -> "+retType;
         else
           return retType + " " + name + args;
       }

embedded/visitor.ts

@@ -30,7 +30,7 @@ module TDev {
               return this.visitGlobalDef(env, n13.name, n13.type, n13.comment);
             case "localDef":
               var n1 = <J.JLocalDef> n;
-              return this.visitLocalDef(env, n1.name, n1.id, n1.type);
+              return this.visitLocalDef(env, n1.name, n1.id, n1.type, n1.isByRef);
             case "localRef":
               var n11 = <J.JLocalRef> n;
               return this.visitLocalRef(env, n11.name, <any> n11.localId);
@@ -115,7 +115,8 @@ module TDev {
         env: T,
         name: string,
         id: string,
-        type: J.JTypeRef): U                                              { throw new Error("Not implemented"); }
+        type: J.JTypeRef,
+        isByRef: boolean): U                                              { throw new Error("Not implemented"); }
       public visitLocalRef(env: T, name: string, id: string): U           { throw new Error("Not implemented"); }
       public visitExprHolder(
         env: T,

rt/cloud.ts

@@ -4,7 +4,7 @@ module TDev.Cloud {
     export var lite = false;
     export var fullTD = true;
     export var litePermissions:StringMap<boolean> = {};
-    var microbitGitTag = "v12";
+    var microbitGitTag = "v13";
 
     export var useEmbeddedGcc = true;
     export var useNativeCompilation = false;