[scope] allow taking address of local in @safe code

src/escape.d

@@ -427,6 +427,7 @@ private bool checkEscapeImpl(Scope* sc, Expression e, bool refs, bool gag)
     bool result = false;
     foreach (VarDeclaration v; er.byvalue)
     {
+        //printf("byvalue %s\n", v.toChars());
         if (v.isDataseg())
             continue;
 
@@ -483,17 +484,34 @@ private bool checkEscapeImpl(Scope* sc, Expression e, bool refs, bool gag)
 
     foreach (VarDeclaration v; er.byref)
     {
+        //printf("byref %s\n", v.toChars());
         if (v.isDataseg())
             continue;
 
         Dsymbol p = v.toParent2();
 
-        if ((v.storage_class & (STCref | STCout)) == 0 && p == sc.func)
+        if ((v.storage_class & (STCref | STCout)) == 0)
         {
-            if (!gag)
-                error(e.loc, "escaping reference to local variable %s", v.toChars());
-            result = true;
-            continue;
+            if (p == sc.func)
+            {
+                if (!gag)
+                    error(e.loc, "escaping reference to local variable %s", v.toChars());
+                result = true;
+                continue;
+            }
+            FuncDeclaration fd = p.isFuncDeclaration();
+            if (fd && sc.func.flags & FUNCFLAGreturnInprocess)
+            {
+                /* Code like:
+                 *   int x;
+                 *   auto dg = () { return &x; }
+                 * Making it:
+                 *   auto dg = () return { return &x; }
+                 * Because dg.ptr points to x, this is returning dt.ptr+offset
+                 */
+                sc.func.storage_class |= STCreturn;
+            }
+
         }
 
         /* Check for returning a ref variable by 'ref', but should be 'return ref'
@@ -540,6 +558,7 @@ private bool checkEscapeImpl(Scope* sc, Expression e, bool refs, bool gag)
 
     foreach (Expression ee; er.byexp)
     {
+        //printf("byexp %s\n", ee.toChars());
         if (!gag)
             error(ee.loc, "escaping reference to stack allocated value returned by %s", ee.toChars());
         result = true;
@@ -795,8 +814,12 @@ private void escapeByValue(Expression e, EscapeByResults* er)
              */
             Type t1 = e.e1.type.toBasetype();
             TypeFunction tf;
+            TypeDelegate dg;
             if (t1.ty == Tdelegate)
+            {
+                dg = cast(TypeDelegate)t1;
                 tf = cast(TypeFunction)(cast(TypeDelegate)t1).next;
+            }
             else if (t1.ty == Tfunction)
                 tf = cast(TypeFunction)t1;
             else
@@ -835,6 +858,15 @@ private void escapeByValue(Expression e, EscapeByResults* er)
                         escapeByRef(dve.e1, er);
                 }
             }
+
+            /* If returning the result of a delegate call, the .ptr
+             * field of the delegate must be checked.
+             */
+            if (dg)
+            {
+                if (tf.isreturn)
+                    e.e1.accept(this);
+            }
         }
     }
 

src/expression.d

@@ -10600,9 +10600,18 @@ extern (C++) final class AddrExp : UnaExp
                 }
                 if (sc.func && !sc.intypeof && !v.isDataseg())
                 {
-                    if (sc.func.setUnsafe())
+                    const(char)* p = v.isParameter() ? "parameter" : "local";
+                    if (global.params.safe)
+                    {
+                        v.storage_class &= ~STCmaybescope;
+                        if (v.storage_class & STCscope && sc.func.setUnsafe())
+                        {
+                            error("cannot take address of scope %s %s in @safe function %s", p, v.toChars(), sc.func.toChars());
+                            return false;
+                        }
+                    }
+                    else if (sc.func.setUnsafe())
                     {
-                        const(char)* p = v.isParameter() ? "parameter" : "local";
                         error("cannot take address of %s %s in @safe function %s", p, v.toChars(), sc.func.toChars());
                         return false;
                     }

src/func.d

@@ -750,8 +750,11 @@ extern (C++) class FuncDeclaration : Declaration
             error("functions cannot be scope");
         }
 
-        if (f.isreturn && !needThis())
+        if (f.isreturn && !needThis() && !isNested())
         {
+            /* Non-static nested functions have a hidden 'this' pointer to which
+             * the 'return' applies
+             */
             error("static member has no 'this' to which 'return' can apply");
         }
 
@@ -2220,7 +2223,18 @@ extern (C++) class FuncDeclaration : Declaration
             f.isnogc = true;
         }
 
-        flags &= ~(FUNCFLAGreturnInprocess | FUNCFLAGinferScope);
+        if (flags & FUNCFLAGreturnInprocess)
+        {
+            flags &= ~FUNCFLAGreturnInprocess;
+            if (storage_class & STCreturn)
+            {
+                if (type == f)
+                    f = cast(TypeFunction)f.copy();
+                f.isreturn = true;
+            }
+        }
+
+        flags &= ~FUNCFLAGinferScope;
 
         // Infer STCscope
         if (parameters)

test/fail_compilation/retscope.d

@@ -214,3 +214,56 @@ void* escape3 (scope void* p) @safe {
     return dg();
 }
 
+/**************************************************/
+
+/*
+TEST_OUTPUT:
+---
+fail_compilation/retscope.d(230): Error: scope variable ptr may not be returned
+---
+*/
+
+alias dg_t = void* delegate () return scope @safe;
+
+void* funretscope(scope dg_t ptr) @safe
+{
+    return ptr();
+}
+
+/*****************************************************/
+
+/*
+TEST_OUTPUT:
+---
+fail_compilation/retscope.d(247): Error: cannot implicitly convert expression (__lambda1) of type void* delegate() pure nothrow @nogc return @safe to void* delegate() @safe
+fail_compilation/retscope.d(247): Error: cannot implicitly convert expression (__lambda1) of type void* delegate() pure nothrow @nogc return @safe to void* delegate() @safe
+fail_compilation/retscope.d(248): Error: cannot implicitly convert expression (__lambda2) of type void* delegate() pure nothrow @nogc return @safe to void* delegate() @safe
+fail_compilation/retscope.d(248): Error: cannot implicitly convert expression (__lambda2) of type void* delegate() pure nothrow @nogc return @safe to void* delegate() @safe
+---
+*/
+
+void escape4() @safe
+{
+    alias FunDG = void* delegate () @safe;
+    int x = 42;
+    scope FunDG f = () return { return &x; };
+    scope FunDG g = ()        { return &x; };
+}
+
+/**************************************************/
+
+/*
+TEST_OUTPUT:
+---
+fail_compilation/retscope.d(267): Error: cannot take address of scope local p in @safe function escape5
+---
+*/
+
+void escape5() @safe
+{
+    int* q;
+    scope int* p;
+    scope int** pp = &q; // ok
+    pp = &p; // error
+}
+