add __rvalue(expression) builtin

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/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 @@
     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 @@
 
     override final bool isLvalue()
     {
-        return true;
+        return !this.rvalue;
     }
 
     override void accept(Visitor v)
@@ -1351,7 +1352,7 @@
 
     override bool isLvalue()
     {
-        return true;
+        return !rvalue;
     }
 
     override void accept(Visitor v)
@@ -1397,7 +1398,7 @@
     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 @@
         /* 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 @@
 
     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 @@
 
     override final bool isLvalue()
     {
-        return true;
+        return !rvalue;
     }
 
     override void accept(Visitor v)
@@ -3303,6 +3304,8 @@
 
     override bool isLvalue()
     {
+        if (rvalue)
+            return false;
         if (e1.op != EXP.structLiteral)
             return true;
         auto vd = var.isVarDeclaration();
@@ -3530,6 +3533,8 @@
 
     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 @@
 
     override bool isLvalue()
     {
-        return true;
+        return !rvalue;
     }
 
     override void accept(Visitor v)
@@ -3777,7 +3782,7 @@
     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 @@
 
     override bool isLvalue()
     {
-        return e1.isLvalue();
+        return !rvalue && e1.isLvalue();
     }
 
     override void accept(Visitor v)
@@ -3891,7 +3896,7 @@
         /* 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 @@
 
     override bool isLvalue()
     {
+        if (rvalue)
+            return false;
         if (type && type.toBasetype().ty == Tvoid)
             return false;
         return true;
@@ -4005,7 +4012,7 @@
 
     override bool isLvalue()
     {
-        return e2.isLvalue();
+        return !rvalue && e2.isLvalue();
     }
 
     override Optional!bool toBool()
@@ -4080,7 +4087,7 @@
 
     override bool isLvalue()
     {
-        return e1.isLvalue();
+        return !rvalue && e1.isLvalue();
     }
 
     override void accept(Visitor v)
@@ -4103,7 +4110,7 @@
 
     override bool isLvalue()
     {
-        return e1.isLvalue();
+        return !rvalue && e1.isLvalue();
     }
 
     override void accept(Visitor v)
@@ -4143,6 +4150,8 @@
 
     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 @@
         {
             return false;
         }
-        return true;
+        return !rvalue;
     }
 
     override void accept(Visitor v)
@@ -4982,7 +4991,7 @@
 
     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();

compiler/src/dmd/expressionsem.d

@@ -3892,6 +3892,8 @@ private extern (C++) final class ExpressionSemanticVisitor : Visitor
             return;
         }
 
+        scope (success) result.rvalue = exp.rvalue;
+
         Dsymbol scopesym;
         Dsymbol s = sc.search(exp.loc, exp.ident, scopesym);
         if (s)

compiler/src/dmd/frontend.h

@@ -2068,6 +2068,7 @@ enum class EXP : uint8_t
     _Generic_ = 125u,
     interval = 126u,
     loweredAssignExp = 127u,
+    rvalue = 128u,
 };
 
 typedef uint64_t dinteger_t;
@@ -2105,6 +2106,7 @@ class Expression : public ASTNode
     Loc loc;
     const EXP op;
     bool parens;
+    bool rvalue;
     size_t size() const;
     static void _init();
     static void deinitialize();
@@ -2888,33 +2890,34 @@ enum class TOK : uint8_t
     wchar_tLiteral = 196u,
     endOfLine = 197u,
     whitespace = 198u,
-    inline_ = 199u,
-    register_ = 200u,
-    restrict_ = 201u,
-    signed_ = 202u,
-    sizeof_ = 203u,
-    typedef_ = 204u,
-    unsigned_ = 205u,
-    volatile_ = 206u,
-    _Alignas_ = 207u,
-    _Alignof_ = 208u,
-    _Atomic_ = 209u,
-    _Bool_ = 210u,
-    _Complex_ = 211u,
-    _Generic_ = 212u,
-    _Imaginary_ = 213u,
-    _Noreturn_ = 214u,
-    _Static_assert_ = 215u,
-    _Thread_local_ = 216u,
-    _assert_ = 217u,
-    _import_ = 218u,
-    __cdecl_ = 219u,
-    __declspec_ = 220u,
-    __stdcall_ = 221u,
-    __thread_ = 222u,
-    __pragma_ = 223u,
-    __int128_ = 224u,
-    __attribute___ = 225u,
+    rvalue = 199u,
+    inline_ = 200u,
+    register_ = 201u,
+    restrict_ = 202u,
+    signed_ = 203u,
+    sizeof_ = 204u,
+    typedef_ = 205u,
+    unsigned_ = 206u,
+    volatile_ = 207u,
+    _Alignas_ = 208u,
+    _Alignof_ = 209u,
+    _Atomic_ = 210u,
+    _Bool_ = 211u,
+    _Complex_ = 212u,
+    _Generic_ = 213u,
+    _Imaginary_ = 214u,
+    _Noreturn_ = 215u,
+    _Static_assert_ = 216u,
+    _Thread_local_ = 217u,
+    _assert_ = 218u,
+    _import_ = 219u,
+    __cdecl_ = 220u,
+    __declspec_ = 221u,
+    __stdcall_ = 222u,
+    __thread_ = 223u,
+    __pragma_ = 224u,
+    __int128_ = 225u,
+    __attribute___ = 226u,
 };
 
 class FuncExp final : public Expression
@@ -5259,18 +5262,18 @@ struct UnionExp final
 private:
     union _AnonStruct_u
     {
-        char exp[30LLU];
+        char exp[31LLU];
         char integerexp[40LLU];
-        char errorexp[30LLU];
+        char errorexp[31LLU];
         char realexp[48LLU];
         char complexexp[64LLU];
         char symoffexp[64LLU];
-        char stringexp[51LLU];
-        char arrayliteralexp[48LLU];
+        char stringexp[59LLU];
+        char arrayliteralexp[56LLU];
         char assocarrayliteralexp[56LLU];
         char structliteralexp[76LLU];
         char compoundliteralexp[40LLU];
-        char nullexp[30LLU];
+        char nullexp[31LLU];
         char dotvarexp[49LLU];
         char addrexp[40LLU];
         char indexexp[74LLU];

compiler/src/dmd/hdrgen.d

@@ -2888,6 +2888,12 @@
         buf.writestring(e.value.toChars());
     }
 
+    if (e.rvalue)
+        buf.writestring("__rvalue(");
+    scope (success)
+        if (e.rvalue)
+            buf.writeByte(')');
+
     switch (e.op)
     {
         default:

compiler/src/dmd/parse.d

@@ -5877,6 +5877,7 @@ class Parser(AST, Lexer = dmd.lexer.Lexer) : Lexer
         case TOK.moduleString:
         case TOK.functionString:
         case TOK.prettyFunction:
+        case TOK.rvalue:
         Lexp:
             {
                 AST.Expression exp = parseExpression();
@@ -8423,6 +8424,15 @@ class Parser(AST, Lexer = dmd.lexer.Lexer) : Lexer
                 e = new AST.TypeidExp(loc, o);
                 break;
             }
+        case TOK.rvalue:
+            {
+                nextToken();
+                check(TOK.leftParenthesis, "`__rvalue`");
+                e = parseAssignExp();
+                e.rvalue = true;
+                check(TOK.rightParenthesis);
+                break;
+            }
         case TOK.traits:
             {
                 /* __traits(identifier, args...)

compiler/src/dmd/tokens.d

@@ -27,6 +27,9 @@ enum TOK : ubyte
 {
     reserved,
 
+    // if this list changes, update
+    // tokens.h, ../tests/cxxfrontend.cc and ../../test/unit/lexer/location_offset.d to match
+
     // Other
     leftParenthesis,
     rightParenthesis,
@@ -249,6 +252,7 @@ enum TOK : ubyte
     wchar_tLiteral,
     endOfLine,  // \n, \r, \u2028, \u2029
     whitespace,
+    rvalue,
 
     // C only keywords
     inline,
@@ -425,6 +429,7 @@ enum EXP : ubyte
     interval,
 
     loweredAssignExp,
+    rvalue,
 }
 
 enum FirstCKeyword = TOK.inline;
@@ -556,6 +561,7 @@ private immutable TOK[] keywords =
     TOK.prettyFunction,
     TOK.shared_,
     TOK.immutable_,
+    TOK.rvalue,
 
     // C only keywords
     TOK.inline,
@@ -680,6 +686,7 @@ extern (C++) struct Token
         TOK.pragma_: "pragma",
         TOK.typeof_: "typeof",
         TOK.typeid_: "typeid",
+        TOK.rvalue: "__rvalue",
         TOK.template_: "template",
         TOK.void_: "void",
         TOK.int8: "byte",