Added a new AST transformation pass called the

"Playground Transform."  This is an
instrumentation pass that adds calls to a
function called playground_log at locations of
interest.  Roughly speaking, these locations are

- Initialization of variables
- Modification of variables
- Expressions returning values
- Application of mutating methods on objects

The playground transform currently only finds
modifications of variables, but the intent is to
make all of these cases work.

It is enabled by a frontend option, and can
also be invoked by calling

swift::performPlaygroundTransform(SF)

which is the way LLDB, its main client, will
use it.

The frontend option is intended for testing,
and indeed I will add tests for this
transformation in the coming week as I bring
more functionality online.


Swift SVN r14801

include/swift/Driver/FrontendOptions.td

@@ -101,6 +101,9 @@ def enable_objc_optional : Flag<["-"], "enable-objc-optional">,
 def print_stats : Flag<["-"], "print-stats">,
   HelpText<"Print various statistics">;
 
+def playground : Flag<["-"], "playground">,
+  HelpText<"Apply the playground transformation">;
+
 def sil_inline_threshold : Separate<["-"], "sil-inline-threshold">,
   MetaVarName<"<50>">,
   HelpText<"Controls the aggressiveness of performance inlining">;

include/swift/Frontend/FrontendOptions.h

@@ -145,6 +145,9 @@ public:
   /// termination.
   bool PrintStats = false;
 
+  /// Indicates whether the playground transformation should be applied.
+  bool Playground = false;
+
   /// Indicates whether standard help should be shown.
   bool PrintHelp = false;
 

include/swift/Subsystems.h

@@ -116,6 +116,10 @@ namespace swift {
   ///                  source file.
   void performNameBinding(SourceFile &SF, unsigned StartElem = 0);
 
+  /// Once parsing and name-binding are complete, this optionally transforms the
+  /// ASTs to add calls to external logging functions.
+  void performPlaygroundTransform(SourceFile &SF);
+  
   /// Once parsing and name-binding are complete, this walks the AST to resolve
   /// types and diagnose problems therein.
   ///

lib/Frontend/CompilerInvocation.cpp

@@ -96,6 +96,10 @@ static bool ParseFrontendArgs(FrontendOptions &Opts, ArgList &Args,
     Opts.PrintStats = true;
   }
 
+  if (Args.hasArg(OPT_playground)) {
+    Opts.Playground = true;
+  }
+
   if (const Arg *A = Args.getLastArg(OPT_help, OPT_help_hidden)) {
     if (A->getOption().matches(OPT_help)) {
       Opts.PrintHelp = true;

lib/Frontend/Frontend.cpp

@@ -308,6 +308,9 @@ void CompilerInstance::performParse() {
                             CurTUElem);
       CurTUElem = MainFile.Decls.size();
     } while (!Done);
+
+    if (Invocation.getFrontendOptions().Playground)
+      performPlaygroundTransform(MainFile);
   }
 
   if (!Invocation.getParseOnly()) {

lib/Sema/CMakeLists.txt

@@ -14,6 +14,7 @@ add_swift_library(swiftSema
   DerivedConformanceEquatableHashable.cpp
   DerivedConformanceRawRepresentable.cpp
   MiscDiagnostics.cpp
+  PlaygroundTransform.cpp
   TypeChecker.cpp
   TypeCheckConstraints.cpp
   TypeCheckExpr.cpp

lib/Sema/PlaygroundTransform.cpp

@@ -0,0 +1,228 @@
+//===--- PlaygroundTransform.cpp - Playground Transform -------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2015 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See http://swift.org/LICENSE.txt for license information
+// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file implements the playground transform for Swift.
+//
+//===----------------------------------------------------------------------===//
+
+#include "swift/AST/ASTContext.h"
+#include "swift/AST/ASTNode.h"
+#include "swift/AST/ASTWalker.h"
+#include "swift/AST/Decl.h"
+#include "swift/AST/Expr.h"
+#include "swift/AST/Module.h"
+#include "swift/AST/NameLookup.h"
+#include "swift/AST/Stmt.h"
+#include "swift/AST/Types.h"
+#include "swift/Sema/CodeCompletionTypeChecking.h"
+#include "swift/Subsystems.h"
+
+using namespace swift;
+
+//===----------------------------------------------------------------------===//
+// performPlaygroundTransform
+//===----------------------------------------------------------------------===//
+
+class Instrumenter {
+private:
+  ASTContext &Context;
+  DeclContext *TypeCheckDC;
+public:
+  Instrumenter (ASTContext &C, DeclContext *DC) :
+    Context(C), TypeCheckDC(DC) { }
+    
+  Stmt *transformStmt(Stmt *S) { 
+    switch (S->getKind()) {
+    default:
+      return S;
+    case StmtKind::Brace:
+      return transformBraceStmt(llvm::cast<BraceStmt>(S));
+    case StmtKind::If:
+      return transformIfStmt(llvm::cast<IfStmt>(S));
+    }
+  }
+    
+  // transform*() return their input if it's unmodified,
+  // or a modified copy of their input otherwise.
+  IfStmt *transformIfStmt(IfStmt *IS) {
+    if (Stmt *TS = IS->getThenStmt()) {
+      Stmt *NTS = transformStmt(TS);
+      if (NTS != TS) {
+        IS->setThenStmt(NTS);
+      }
+    }
+
+    if (Stmt *ES = IS->getElseStmt()) {
+      Stmt *NES = transformStmt(ES);
+      if (NES != ES) {
+        IS->setElseStmt(NES);
+      }
+    }
+
+    return IS;
+  }
+
+  BraceStmt *transformBraceStmt(BraceStmt *BS) {
+    llvm::ArrayRef<ASTNode> OriginalElements = BS->getElements();
+    typedef llvm::SmallVector<swift::ASTNode, 3> ElementVector;
+    ElementVector Elements(OriginalElements.begin(),
+                           OriginalElements.end());
+
+    bool Modified = false;
+
+    for (size_t EI = 0;
+         EI != Elements.size();
+         ++EI) {
+      swift::ASTNode &Element = Elements[EI];
+      if (Expr *E = Element.dyn_cast<Expr*>()) {
+        if (AssignExpr *AE = llvm::dyn_cast<AssignExpr>(E)) {
+          Expr *Log = logAssignExpr(AE);
+          if (Log) {
+            Modified = true;
+            Elements.insert(Elements.begin() + (EI + 1), Log);
+            ++EI;
+          }
+        }
+      } else if (Stmt *S = Element.dyn_cast<Stmt*>()) {
+        Stmt *NS = transformStmt(S);
+        if (NS != S) {
+          Modified = true;
+          Elements[EI] = NS;
+        }
+      } else if (Decl *D = Element.dyn_cast<Decl*>()) {
+        (void)D;
+      }
+    }
+
+    if (Modified) {
+      return swift::BraceStmt::create(Context, BS->getLBraceLoc(),
+                                      Context.AllocateCopy(Elements),
+                                      BS->getRBraceLoc());
+    } else {
+      return BS;
+    }
+  }
+
+  // log*() functions return a newly-created log expression to be inserted
+  // after the expression they're looking at.
+  Expr *logAssignExpr(AssignExpr *AE) {
+    Expr *Dest = AE->getDest();
+    if (DeclRefExpr *DRE = llvm::dyn_cast<DeclRefExpr>(Dest)) {
+      return buildLoggerCall(DRE->getDecl());
+    }
+    return nullptr;
+  }
+
+  Expr *buildLoggerCall(ValueDecl *VD) {
+    Expr *Header = new (Context) StringLiteralExpr("", SourceRange());
+    Header->setImplicit(true);
+
+    Expr *MaxChildren = new (Context) IntegerLiteralExpr("0", SourceLoc(),
+                                                         true);
+
+    Expr *MaxDepth = new (Context) IntegerLiteralExpr("0", SourceLoc(),
+                                                      true);
+
+    Expr *ArgExprs[] = {
+        new (Context) DeclRefExpr(ConcreteDeclRef(VD),
+                                  SourceLoc(),
+                                  true, // implicit
+                                  false, // uses direct property access
+                                  Type()),
+        Header,
+        MaxChildren,
+        MaxDepth
+      };
+
+    TupleExpr *Args = new (Context) TupleExpr(SourceLoc(),
+                                              Context.AllocateCopy(ArgExprs),
+                                              (Identifier*)nullptr,
+                                              SourceLoc(),
+                                              false, // hasTrailingClosure
+                                              true, // implicit
+                                              Type());
+
+    UnresolvedDeclRefExpr *LoggerRef =
+      new (Context) UnresolvedDeclRefExpr(
+        Context.getIdentifier("playground_log"),
+        DeclRefKind::Ordinary,
+        SourceLoc());
+    LoggerRef->setImplicit(true);
+
+    Expr *Call = new (Context) CallExpr(LoggerRef, Args, true, Type());
+
+    if (!typeCheckCompletionContextExpr(Context, TypeCheckDC, Call)) {
+      return nullptr;
+    }
+
+    return Call;
+  }
+};
+
+void swift::performPlaygroundTransform(SourceFile &SF) {
+  class ExpressionFinder : public ASTWalker {
+    FuncDecl *WrappedDecl = nullptr;
+    FuncDecl *ExpressionDecl = nullptr;
+    StringRef WrappedName = "__lldb_wrapped_expr";
+    StringRef ExpressionName = "__lldb_expr";
+  public:
+    virtual bool walkToDeclPre(Decl *D) {
+      if (FuncDecl *FD = llvm::dyn_cast<FuncDecl>(D)) {
+        StringRef FuncName = FD->getName().str();
+        if (!FuncName.endswith(WrappedName)) {
+          WrappedDecl = FD;
+          return false;
+        } else if (!FuncName.endswith(ExpressionName)) {
+          ExpressionDecl = FD;
+          return false;
+        }
+      }
+      return true;
+    }
+    FuncDecl *getFunctionToTransform() {
+      return WrappedDecl ? WrappedDecl : ExpressionDecl;
+    }
+  };
+
+  ExpressionFinder EF;
+  for (Decl* D : SF.Decls) {
+    D->walk(EF);
+  }
+
+  if (FuncDecl *FuncToTransform = EF.getFunctionToTransform()) {
+    if (BraceStmt *Body = FuncToTransform->getBody()) {
+      ASTContext &Context(SF.getASTContext());
+
+      Module *LoggerModule = Context.getModule(
+        std::make_pair(Context.getIdentifier("PlaygroundLoggerLibrary"),
+                       SourceLoc()));
+
+      if (LoggerModule)
+      {
+        SmallVector<ValueDecl*, 1> LoggerDecls;
+
+        LoggerModule->lookupValue(Module::AccessPathTy(),
+                                  Context.getIdentifier("playground_log"),
+                                  NLKind::UnqualifiedLookup,
+                                  LoggerDecls);
+
+        if (LoggerDecls.size() == 1) {
+          Instrumenter I(Context, FuncToTransform);
+          BraceStmt *NewBody = I.transformBraceStmt(Body);
+          if (NewBody != Body) {
+            FuncToTransform->setBody(NewBody);
+          }
+        }
+      }
+    }
+  }
+}