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72
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1 module dmd.NullExp;
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2
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114
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3 import dmd.common;
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72
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4 import dmd.Expression;
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5 import dmd.backend.elem;
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6 import dmd.InterState;
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7 import dmd.MATCH;
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8 import dmd.Type;
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9 import dmd.TY;
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10 import dmd.TypeTypedef;
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11 import dmd.OutBuffer;
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12 import dmd.Loc;
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13 import dmd.Scope;
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14 import dmd.IRState;
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15 import dmd.HdrGenState;
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16 import dmd.TOK;
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17 import dmd.backend.dt_t;
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18 import dmd.backend.Util;
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19
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0
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20 class NullExp : Expression
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21 {
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22 ubyte committed;
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23
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135
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24 this(Loc loc, Type type = null)
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72
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25 {
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178
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26 register();
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0
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27 super(loc, TOK.TOKnull, NullExp.sizeof);
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135
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28 this.type = type;
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0
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29 }
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30
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72
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31 override Expression semantic(Scope sc)
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0
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32 {
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72
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33 version (LOGSEMANTIC) {
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34 printf("NullExp.semantic('%s')\n", toChars());
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35 }
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36 // null is the same as (void*)0
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37 if (!type)
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38 type = Type.tvoid.pointerTo();
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39
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0
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40 return this;
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41 }
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42
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72
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43 override bool isBool(bool result)
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0
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44 {
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45 assert(false);
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46 }
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47
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72
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48 override int isConst()
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0
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49 {
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63
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50 return 0;
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0
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51 }
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52
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72
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53 override void toCBuffer(OutBuffer buf, HdrGenState* hgs)
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0
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54 {
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55 buf.writestring("null");
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56 }
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57
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72
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58 override void toMangleBuffer(OutBuffer buf)
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0
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59 {
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64
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60 buf.writeByte('n');
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0
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61 }
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62
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63 override MATCH implicitConvTo(Type t)
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0
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64 {
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65 static if (false) {
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66 printf("NullExp.implicitConvTo(this=%s, type=%s, t=%s, committed = %d)\n",
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67 toChars(), type.toChars(), t.toChars(), committed);
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68 }
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69 if (this.type.equals(t))
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70 return MATCH.MATCHexact;
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71
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72 /* Allow implicit conversions from invariant to mutable|const,
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73 * and mutable to invariant. It works because, after all, a null
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74 * doesn't actually point to anything.
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75 */
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76 if (t.invariantOf().equals(type.invariantOf()))
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77 return MATCH.MATCHconst;
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78
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79 // null implicitly converts to any pointer type or dynamic array
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80 if (type.ty == TY.Tpointer && type.nextOf().ty == TY.Tvoid)
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81 {
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82 if (t.ty == TY.Ttypedef)
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83 t = (cast(TypeTypedef)t).sym.basetype;
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84 if (t.ty == TY.Tpointer || t.ty == TY.Tarray ||
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85 t.ty == TY.Taarray || t.ty == TY.Tclass ||
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86 t.ty == TY.Tdelegate)
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87 {
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88 return committed ? MATCH.MATCHconvert : MATCH.MATCHexact;
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89 }
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90 }
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91
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92 return Expression.implicitConvTo(t);
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93 }
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94
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72
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95 override Expression castTo(Scope sc, Type t)
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96 {
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72
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97 NullExp e;
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98 Type tb;
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99
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100 //printf("NullExp::castTo(t = %p)\n", t);
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101 if (type is t)
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102 {
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103 committed = 1;
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104 return this;
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105 }
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106
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107 e = cast(NullExp)copy();
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108 e.committed = 1;
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109 tb = t.toBasetype();
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110 e.type = type.toBasetype();
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111
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112 if (tb !is e.type)
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113 {
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114 // null implicitly converts to any pointer type or dynamic array
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115 if (e.type.ty == TY.Tpointer && e.type.nextOf().ty == TY.Tvoid &&
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116 (tb.ty == TY.Tpointer || tb.ty == TY.Tarray || tb.ty == TY.Taarray ||
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117 tb.ty == TY.Tdelegate))
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118 {
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119 static if (false) {
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120 if (tb.ty == TY.Tdelegate)
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121 {
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122 TypeDelegate td = cast(TypeDelegate)tb;
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123 TypeFunction tf = cast(TypeFunction)td.nextOf();
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124
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125 if (!tf.varargs && !(tf.arguments && tf.arguments.dim))
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126 {
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127 return Expression.castTo(sc, t);
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128 }
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129 }
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130 }
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131 }
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132 else
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133 {
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134 return e.Expression.castTo(sc, t);
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135 }
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136 }
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137 e.type = t;
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0
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138 return e;
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139 }
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140
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72
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141 override Expression interpret(InterState istate)
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0
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142 {
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123
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143 return this;
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0
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144 }
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145
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72
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146 override elem* toElem(IRState* irs)
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0
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147 {
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148 return el_long(type.totym(), 0);
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149 }
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150
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72
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151 override dt_t** toDt(dt_t** pdt)
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0
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152 {
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72
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153 assert(type);
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0
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154 return dtnzeros(pdt, cast(uint)type.size());
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155 }
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156 }
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157
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