2nd try at __rvalue(expression)

compiler/src/dmd/aggregate.h

@@ -185,6 +185,8 @@ class StructDeclaration : public AggregateDeclaration
     bool hasNoFields(bool v);
     bool hasCopyCtor() const;       // copy constructor
     bool hasCopyCtor(bool v);
+    bool hasMoveCtor() const;       // move constructor
+    bool hasMoveCtor(bool v);
     // Even if struct is defined as non-root symbol, some built-in operations
     // (e.g. TypeidExp, NewExp, ArrayLiteralExp, etc) request its TypeInfo.
     // For those, today TypeInfo_Struct is generated in COMDAT.

compiler/src/dmd/astbase.d

@@ -4548,6 +4548,7 @@ struct ASTBase
         EXP op;
         ubyte size;
         ubyte parens;
+        ubyte rvalue;              // consider this an rvalue, even if it is an lvalue
         Type type;
         Loc loc;
 

compiler/src/dmd/clone.d

@@ -1610,13 +1610,15 @@ private Statement generateCopyCtorBody(StructDeclaration sd)
  * Params:
  *  sd = the `struct` for which the copy constructor is generated
  *  hasCpCtor = set to true if a copy constructor is already present
+ *  hasMoveCtor = set to true if a move constructor is already present
  *
  * Returns:
  *  `true` if one needs to be generated
  *  `false` otherwise
  */
-bool needCopyCtor(StructDeclaration sd, out bool hasCpCtor)
+bool needCopyCtor(StructDeclaration sd, out bool hasCpCtor, out bool hasMoveCtor)
 {
+    //printf("needCopyCtor() %s\n", sd.toChars());
     if (global.errors)
         return false;
 
@@ -1648,14 +1650,17 @@ bool needCopyCtor(StructDeclaration sd, out bool hasCpCtor)
             return 0;
         }
 
-        if (isRvalueConstructor(sd, ctorDecl))
+        if (ctorDecl.isMoveCtor)
             rvalueCtor = ctorDecl;
         return 0;
     });
 
+    if (rvalueCtor)
+        hasMoveCtor = true;
+
     if (cpCtor)
     {
-        if (rvalueCtor)
+        if (0 && rvalueCtor)
         {
             .error(sd.loc, "`struct %s` may not define both a rvalue constructor and a copy constructor", sd.toChars());
             errorSupplemental(rvalueCtor.loc,"rvalue constructor defined here");
@@ -1710,17 +1715,18 @@ LcheckFields:
  * Params:
  *  sd = the `struct` for which the copy constructor is generated
  *  sc = the scope where the copy constructor is generated
+ *  hasMoveCtor = set to true when a move constructor is also detected
  *
  * Returns:
  *  `true` if `struct` sd defines a copy constructor (explicitly or generated),
  *  `false` otherwise.
  * References:
  *   https://dlang.org/spec/struct.html#struct-copy-constructor
  */
-bool buildCopyCtor(StructDeclaration sd, Scope* sc)
+bool buildCopyCtor(StructDeclaration sd, Scope* sc, out bool hasMoveCtor)
 {
     bool hasCpCtor;
-    if (!needCopyCtor(sd, hasCpCtor))
+    if (!needCopyCtor(sd, hasCpCtor, hasMoveCtor))
         return hasCpCtor;
 
     //printf("generating copy constructor for %s\n", sd.toChars());

compiler/src/dmd/declaration.h

@@ -782,6 +782,7 @@ class CtorDeclaration final : public FuncDeclaration
 {
 public:
     d_bool isCpCtor;
+    d_bool isMoveCtor;
     CtorDeclaration *syntaxCopy(Dsymbol *) override;
     const char *kind() const override;
     const char *toChars() const override;

compiler/src/dmd/dscope.d

@@ -24,6 +24,7 @@ import dmd.dclass;
 import dmd.declaration;
 import dmd.dmodule;
 import dmd.doc;
+import dmd.dstruct;
 import dmd.dsymbol;
 import dmd.dsymbolsem;
 import dmd.dtemplate;
@@ -146,6 +147,7 @@ extern (C++) struct Scope
 
     AliasDeclaration aliasAsg; /// if set, then aliasAsg is being assigned a new value,
                                /// do not set wasRead for it
+    StructDeclaration argStruct;    /// elimiate recursion when looking for rvalue construction
 
     extern (D) __gshared Scope* freelist;
 

compiler/src/dmd/dstruct.d

@@ -101,6 +101,7 @@ extern (C++) class StructDeclaration : AggregateDeclaration
         bool hasIdentityEquals;     // true if has identity opEquals
         bool hasNoFields;           // has no fields
         bool hasCopyCtor;           // copy constructor
+        bool hasMoveCtor;           // move constructor
         bool hasPointerField;       // members with indirections
         bool hasVoidInitPointers;   // void-initialized unsafe fields
         bool hasUnsafeBitpatterns;  // @system members, pointers, bool
@@ -320,11 +321,13 @@ extern (C++) class StructDeclaration : AggregateDeclaration
         import dmd.clone;
 
         bool hasCpCtorLocal;
-        needCopyCtor(this, hasCpCtorLocal);
+        bool hasMoveCtorLocal;
+        needCopyCtor(this, hasCpCtorLocal, hasMoveCtorLocal);
 
         if (enclosing                      || // is nested
             search(this, loc, Id.postblit) || // has postblit
             search(this, loc, Id.dtor)     || // has destructor
+            hasMoveCtorLocal               || // has move constructor
             hasCpCtorLocal)                   // has copy constructor
         {
             ispod = ThreeState.no;

compiler/src/dmd/dsymbolsem.d

@@ -256,6 +256,9 @@ Return:
 */
 bool checkHasBothRvalueAndCpCtor(StructDeclaration sd, CtorDeclaration ctor, TemplateInstance ti)
 {
+    /* cannot use ctor.isMoveCtor because semantic pass may not have been run yet,
+     * so use isRvalueConstructor()
+     */
     if (sd && sd.hasCopyCtor && isRvalueConstructor(sd, ctor))
     {
         .error(ctor.loc, "cannot define both an rvalue constructor and a copy constructor for `struct %s`", sd.toChars());
@@ -280,6 +283,7 @@ bool checkHasBothRvalueAndCpCtor(StructDeclaration sd, CtorDeclaration ctor, Tem
  */
 bool isRvalueConstructor(StructDeclaration sd, CtorDeclaration ctor)
 {
+    // note commonality with setting isMoveCtor in the semantic code for CtorDeclaration
     auto tf = ctor.type.isTypeFunction();
     const dim = tf.parameterList.length;
     if (dim == 1 || (dim > 1 && tf.parameterList[1].defaultArg))
@@ -2399,7 +2403,7 @@ private extern(C++) final class DsymbolSemanticVisitor : Visitor
 
     override void visit(CtorDeclaration ctd)
     {
-        //printf("CtorDeclaration::semantic() %s\n", toChars());
+        //printf("CtorDeclaration::semantic() %p %s\n", ctd, ctd.toChars());
         if (ctd.semanticRun >= PASS.semanticdone)
             return;
         if (ctd._scope)
@@ -2482,12 +2486,15 @@ private extern(C++) final class DsymbolSemanticVisitor : Visitor
             }
             else if ((dim == 1 || (dim > 1 && tf.parameterList[1].defaultArg)))
             {
-                //printf("tf: %s\n", tf.toChars());
+                //printf("tf: %s\n", toChars(tf));
                 auto param = tf.parameterList[0];
-                if (param.storageClass & STC.ref_ && param.type.mutableOf().unSharedOf() == sd.type.mutableOf().unSharedOf())
+                if (param.type.mutableOf().unSharedOf() == sd.type.mutableOf().unSharedOf())
                 {
-                    //printf("copy constructor\n");
-                    ctd.isCpCtor = true;
+                    //printf("copy constructor %p\n", ctd);
+                    if (param.storageClass & STC.ref_)
+                        ctd.isCpCtor = true;            // copy constructor
+                    else
+                        ctd.isMoveCtor = true;          // move constructor
                 }
             }
         }
@@ -2978,7 +2985,10 @@ private extern(C++) final class DsymbolSemanticVisitor : Visitor
 
         buildDtors(sd, sc2);
 
-        sd.hasCopyCtor = buildCopyCtor(sd, sc2);
+        bool hasMoveCtor;
+        sd.hasCopyCtor = buildCopyCtor(sd, sc2, hasMoveCtor);
+        sd.hasMoveCtor = hasMoveCtor;
+
         sd.postblit = buildPostBlit(sd, sc2);
 
         buildOpAssign(sd, sc2);

compiler/src/dmd/e2ir.d

@@ -5532,6 +5532,8 @@ elem *callfunc(const ref Loc loc,
                     v = ve.var.isVarDeclaration();
                 bool copy = !(v && (v.isArgDtorVar || v.storage_class & STC.rvalue)); // copy unless the destructor is going to be run on it
                                                     // then assume the frontend took care of the copying and pass it by ref
+                if (arg.rvalue)                     // marked with __rvalue
+                    copy = false;
 
                 elems[i] = addressElem(ea, arg.type, copy);
                 continue;

compiler/src/dmd/expression.d

@@ -297,6 +297,7 @@ extern (C++) abstract class Expression : ASTNode
     Loc loc;        // file location
     const EXP op;   // to minimize use of dynamic_cast
     bool parens;    // if this is a parenthesized expression
+    bool rvalue;    // true if this is considered to be an rvalue, even if it is an lvalue
 
     extern (D) this(const ref Loc loc, EXP op) scope @safe
     {
@@ -1307,7 +1308,7 @@ extern (C++) class IdentifierExp : Expression
 
     override final bool isLvalue()
     {
-        return true;
+        return !this.rvalue;
     }
 
     override void accept(Visitor v)
@@ -1351,7 +1352,7 @@ extern (C++) final class DsymbolExp : Expression
 
     override bool isLvalue()
     {
-        return true;
+        return !rvalue;
     }
 
     override void accept(Visitor v)
@@ -1397,7 +1398,7 @@ extern (C++) class ThisExp : Expression
     override final bool isLvalue()
     {
         // Class `this` should be an rvalue; struct `this` should be an lvalue.
-        return type.toBasetype().ty != Tclass;
+        return !rvalue && type.toBasetype().ty != Tclass;
     }
 
     override void accept(Visitor v)
@@ -1782,7 +1783,7 @@ extern (C++) final class StringExp : Expression
         /* string literal is rvalue in default, but
          * conversion to reference of static array is only allowed.
          */
-        return (type && type.toBasetype().ty == Tsarray);
+        return !rvalue && (type && type.toBasetype().ty == Tsarray);
     }
 
     /********************************
@@ -2719,7 +2720,7 @@ extern (C++) final class VarExp : SymbolExp
 
     override bool isLvalue()
     {
-        if (var.storage_class & (STC.lazy_ | STC.rvalue | STC.manifest))
+        if (rvalue || var.storage_class & (STC.lazy_ | STC.rvalue | STC.manifest))
             return false;
         return true;
     }
@@ -3098,7 +3099,7 @@ extern (C++) class BinAssignExp : BinExp
 
     override final bool isLvalue()
     {
-        return true;
+        return !rvalue;
     }
 
     override void accept(Visitor v)
@@ -3303,6 +3304,8 @@ extern (C++) final class DotVarExp : UnaExp
 
     override bool isLvalue()
     {
+        if (rvalue)
+            return false;
         if (e1.op != EXP.structLiteral)
             return true;
         auto vd = var.isVarDeclaration();
@@ -3530,6 +3533,8 @@ extern (C++) final class CallExp : UnaExp
 
     override bool isLvalue()
     {
+        if (rvalue)
+            return false;
         Type tb = e1.type.toBasetype();
         if (tb.ty == Tdelegate || tb.ty == Tpointer)
             tb = tb.nextOf();
@@ -3648,7 +3653,7 @@ extern (C++) final class PtrExp : UnaExp
 
     override bool isLvalue()
     {
-        return true;
+        return !rvalue;
     }
 
     override void accept(Visitor v)
@@ -3777,7 +3782,7 @@ extern (C++) final class CastExp : UnaExp
     override bool isLvalue()
     {
         //printf("e1.type = %s, to.type = %s\n", e1.type.toChars(), to.toChars());
-        if (!e1.isLvalue())
+        if (rvalue || !e1.isLvalue())
             return false;
         return (to.ty == Tsarray && (e1.type.ty == Tvector || e1.type.ty == Tsarray)) ||
             e1.type.mutableOf.unSharedOf().equals(to.mutableOf().unSharedOf());
@@ -3834,7 +3839,7 @@ extern (C++) final class VectorArrayExp : UnaExp
 
     override bool isLvalue()
     {
-        return e1.isLvalue();
+        return !rvalue && e1.isLvalue();
     }
 
     override void accept(Visitor v)
@@ -3891,7 +3896,7 @@ extern (C++) final class SliceExp : UnaExp
         /* slice expression is rvalue in default, but
          * conversion to reference of static array is only allowed.
          */
-        return (type && type.toBasetype().ty == Tsarray);
+        return !rvalue && (type && type.toBasetype().ty == Tsarray);
     }
 
     override Optional!bool toBool()
@@ -3956,6 +3961,8 @@ extern (C++) final class ArrayExp : UnaExp
 
     override bool isLvalue()
     {
+        if (rvalue)
+            return false;
         if (type && type.toBasetype().ty == Tvoid)
             return false;
         return true;
@@ -4005,7 +4012,7 @@ extern (C++) final class CommaExp : BinExp
 
     override bool isLvalue()
     {
-        return e2.isLvalue();
+        return !rvalue && e2.isLvalue();
     }
 
     override Optional!bool toBool()
@@ -4080,7 +4087,7 @@ extern (C++) final class DelegatePtrExp : UnaExp
 
     override bool isLvalue()
     {
-        return e1.isLvalue();
+        return !rvalue && e1.isLvalue();
     }
 
     override void accept(Visitor v)
@@ -4103,7 +4110,7 @@ extern (C++) final class DelegateFuncptrExp : UnaExp
 
     override bool isLvalue()
     {
-        return e1.isLvalue();
+        return !rvalue && e1.isLvalue();
     }
 
     override void accept(Visitor v)
@@ -4143,6 +4150,8 @@ extern (C++) final class IndexExp : BinExp
 
     override bool isLvalue()
     {
+        if (rvalue)
+            return false;
         auto t1b = e1.type.toBasetype();
         if (t1b.isTypeAArray() || t1b.isTypeSArray() ||
             (e1.isIndexExp() && t1b != t1b.isTypeDArray()))
@@ -4251,7 +4260,7 @@ extern (C++) class AssignExp : BinExp
         {
             return false;
         }
-        return true;
+        return !rvalue;
     }
 
     override void accept(Visitor v)
@@ -4982,7 +4991,7 @@ extern (C++) final class CondExp : BinExp
 
     override bool isLvalue()
     {
-        return e1.isLvalue() && e2.isLvalue();
+        return !rvalue && e1.isLvalue() && e2.isLvalue();
     }
 
     override void accept(Visitor v)

compiler/src/dmd/expression.h

@@ -78,6 +78,7 @@ class Expression : public ASTNode
     Loc loc;                    // file location
     EXP op;                     // to minimize use of dynamic_cast
     d_bool parens;              // if this is a parenthesized expression
+    d_bool rvalue;              // consider this an rvalue, even if it is an lvalue
 
     size_t size() const;
     static void _init();