diff --git a/std/array.d b/std/array.d
index 577b04f2f6f..410c5f6b435 100644
--- a/std/array.d
+++ b/std/array.d
@@ -120,7 +120,7 @@ unittest
     {
         int x;
         this(int y) { x = y; }
-        override string toString() { return .to!string(x); }
+        override string toString() const { return .to!string(x); }
     }
     auto c = array([new C(1), new C(2)][]);
     //writeln(c);
diff --git a/std/conv.d b/std/conv.d
index 1becb418950..7306ff0b9e0 100644
--- a/std/conv.d
+++ b/std/conv.d
@@ -991,7 +991,7 @@ unittest
 
     class A
     {
-        override string toString() { return "an A"; }
+        override string toString() const { return "an A"; }
     }
     A a;
     assert(to!string(a) == "null");
@@ -999,7 +999,7 @@ unittest
     assert(to!string(a) == "an A");
 
     // Bug 7660
-    class C { override string toString() { return "C"; } }
+    class C { override string toString() const { return "C"; } }
     struct S { C c; alias c this; }
     S s; s.c = new C();
     assert(to!string(s) == "C");
diff --git a/std/csv.d b/std/csv.d
index 9d4363ecbe6..abcd4fb10ef 100644
--- a/std/csv.d
+++ b/std/csv.d
@@ -124,7 +124,7 @@ class CSVException : Exception
         this.col = col;
     }
 
-    override string toString() {
+    override string toString() const {
         return "(Row: " ~ to!string(row) ~
               ", Col: " ~ to!string(col) ~ ") " ~ msg;
     }
diff --git a/std/format.d b/std/format.d
index 691cb6b1fbe..eca6b70a028 100644
--- a/std/format.d
+++ b/std/format.d
@@ -1219,14 +1219,15 @@ unittest
 
     class C1 { bool val; alias val this; this(bool v){ val = v; } }
     class C2 { bool val; alias val this; this(bool v){ val = v; }
-               override string toString(){ return "C"; } }
+               override string toString() const { return "C"; } }
     formatTest( new C1(false), "false" );
     formatTest( new C1(true),  "true" );
     formatTest( new C2(false), "C" );
     formatTest( new C2(true),  "C" );
 
     struct S1 { bool val; alias val this; }
-    struct S2 { bool val; alias val this; string toString(){ return "S"; } }
+    struct S2 { bool val; alias val this;
+                string toString() const { return "S"; } }
     formatTest( S1(false), "false" );
     formatTest( S1(true),  "true"  );
     formatTest( S2(false), "S" );
@@ -1417,12 +1418,13 @@ unittest
 
     class C1 { long val; alias val this; this(long v){ val = v; } }
     class C2 { long val; alias val this; this(long v){ val = v; }
-               override string toString(){ return "C"; } }
+               override string toString() const { return "C"; } }
     formatTest( new C1(10), "10" );
     formatTest( new C2(10), "C" );
 
     struct S1 { long val; alias val this; }
-    struct S2 { long val; alias val this; string toString(){ return "S"; } }
+    struct S2 { long val; alias val this;
+                string toString() const { return "S"; } }
     formatTest( S1(10), "10" );
     formatTest( S2(10), "S" );
 }
@@ -1502,12 +1504,13 @@ unittest
 
     class C1 { double val; alias val this; this(double v){ val = v; } }
     class C2 { double val; alias val this; this(double v){ val = v; }
-               override string toString(){ return "C"; } }
+               override string toString() const { return "C"; } }
     formatTest( new C1(2.25), "2.25" );
     formatTest( new C2(2.25), "C" );
 
     struct S1 { double val; alias val this; }
-    struct S2 { double val; alias val this; string toString(){ return "S"; } }
+    struct S2 { double val; alias val this;
+                string toString() const { return "S"; } }
     formatTest( S1(2.25), "2.25" );
     formatTest( S2(2.25), "S" );
 }
@@ -1542,12 +1545,13 @@ unittest
 
     class C1 { cdouble val; alias val this; this(cdouble v){ val = v; } }
     class C2 { cdouble val; alias val this; this(cdouble v){ val = v; }
-               override string toString(){ return "C"; } }
+               override string toString() const { return "C"; } }
     formatTest( new C1(3+2.25i), "3+2.25i" );
     formatTest( new C2(3+2.25i), "C" );
 
     struct S1 { cdouble val; alias val this; }
-    struct S2 { cdouble val; alias val this; string toString(){ return "S"; } }
+    struct S2 { cdouble val; alias val this;
+                string toString() const { return "S"; } }
     formatTest( S1(3+2.25i), "3+2.25i" );
     formatTest( S2(3+2.25i), "S" );
 }
@@ -1580,12 +1584,13 @@ unittest
 
     class C1 { idouble val; alias val this; this(idouble v){ val = v; } }
     class C2 { idouble val; alias val this; this(idouble v){ val = v; }
-               override string toString(){ return "C"; } }
+               override string toString() const { return "C"; } }
     formatTest( new C1(2.25i), "2.25i" );
     formatTest( new C2(2.25i), "C" );
 
     struct S1 { idouble val; alias val this; }
-    struct S2 { idouble val; alias val this; string toString(){ return "S"; } }
+    struct S2 { idouble val; alias val this;
+                string toString() const { return "S"; } }
     formatTest( S1(2.25i), "2.25i" );
     formatTest( S2(2.25i), "S" );
 }
@@ -1616,12 +1621,13 @@ unittest
 
     class C1 { char val; alias val this; this(char v){ val = v; } }
     class C2 { char val; alias val this; this(char v){ val = v; }
-               override string toString(){ return "C"; } }
+               override string toString() const { return "C"; } }
     formatTest( new C1('c'), "c" );
     formatTest( new C2('c'), "C" );
 
     struct S1 { char val; alias val this; }
-    struct S2 { char val; alias val this; string toString(){ return "S"; } }
+    struct S2 { char val; alias val this;
+                string toString() const { return "S"; } }
     formatTest( S1('c'), "c" );
     formatTest( S2('c'), "S" );
 }
@@ -1659,10 +1665,11 @@ unittest
 unittest
 {
     class  C3 { string val; alias val this; this(string s){ val = s; }
-                override string toString(){ return "C"; } }
+                override string toString() const { return "C"; } }
     formatTest( new C3("c3"), "C" );
 
-    struct S3 { string val; alias val this; string toString(){ return "S"; } }
+    struct S3 { string val; alias val this;
+                string toString() const { return "S"; } }
     formatTest( S3("s3"), "S" );
 }
 
@@ -1731,7 +1738,7 @@ unittest
       }
 
       static if (flags & 4)
-        string toString(){ return "S"; }
+        string toString() const { return "S"; }
     }
     formatTest(S!0b000([0, 1, 2]), "S!(0)([0, 1, 2])");
     formatTest(S!0b001([0, 1, 2]), "[0, 1, 2]");        // Test for bug 7628
@@ -1758,7 +1765,7 @@ unittest
       }
 
       static if (flags & 4)
-        override string toString(){ return "C"; }
+        override string toString() const { return "C"; }
     }
     formatTest(new C!0b000([0, 1, 2]), (new C!0b000([])).toString());
     formatTest(new C!0b001([0, 1, 2]), "[0, 1, 2]");    // Test for bug 7628
@@ -2244,12 +2251,13 @@ unittest
 {
     class C1 { int[char] val; alias val this; this(int[char] v){ val = v; } }
     class C2 { int[char] val; alias val this; this(int[char] v){ val = v; }
-               override string toString(){ return "C"; } }
+               override string toString() const { return "C"; } }
     formatTest( new C1(['c':1, 'd':2]), `['c':1, 'd':2]` );
     formatTest( new C2(['c':1, 'd':2]), "C" );
 
     struct S1 { int[char] val; alias val this; }
-    struct S2 { int[char] val; alias val this; string toString(){ return "S"; } }
+    struct S2 { int[char] val; alias val this;
+                string toString() const { return "S"; } }
     formatTest( S1(['c':1, 'd':2]), `['c':1, 'd':2]` );
     formatTest( S2(['c':1, 'd':2]), "S" );
 }
@@ -2417,7 +2425,7 @@ unittest
     class C4
     {
         mixin(inputRangeCode);
-        override string toString() { return "[012]"; }
+        override string toString() const { return "[012]"; }
     }
     class C5
     {
@@ -2467,7 +2475,7 @@ unittest
     interface Whatever {}
     class C : Whatever
     {
-        override @property string toString() { return "ab"; }
+        override @property string toString() const { return "ab"; }
     }
     Whatever val = new C;
     formatTest( val, "ab" );
@@ -2525,9 +2533,9 @@ if ((is(T == struct) || is(T == union)) && (hasToString!(T, Char) || !isBuiltinT
 unittest
 {
     // bug 4638
-    struct U8  {  string toString() { return "blah"; } }
-    struct U16 { wstring toString() { return "blah"; } }
-    struct U32 { dstring toString() { return "blah"; } }
+    struct U8  {  string toString() const { return "blah"; } }
+    struct U16 { wstring toString() const { return "blah"; } }
+    struct U32 { dstring toString() const { return "blah"; } }
     formatTest( U8(), "blah" );
     formatTest( U16(), "blah" );
     formatTest( U32(), "blah" );
@@ -2558,7 +2566,7 @@ unittest
     {
         int n;
         string s;
-        string toString(){ return s; }
+        string toString() const { return s; }
     }
     U2 u2;
     u2.s = "hello";
@@ -2705,7 +2713,7 @@ unittest
     // Test for issue 7869
     struct S
     {
-        string toString(){ return ""; }
+        string toString() const { return ""; }
     }
     S* p = null;
     formatTest( p, "null" );
diff --git a/std/outbuffer.d b/std/outbuffer.d
index 32730b2aa3c..e2f6f6855b8 100644
--- a/std/outbuffer.d
+++ b/std/outbuffer.d
@@ -242,7 +242,7 @@ class OutBuffer
      * Convert internal buffer to array of chars.
      */
 
-    override string toString()
+    override string toString() const
     {
         //printf("OutBuffer.toString()\n");
         return cast(string) data[0 .. offset].idup;
diff --git a/std/socketstream.d b/std/socketstream.d
index e89358eb6a4..5ec4bfb3b5b 100644
--- a/std/socketstream.d
+++ b/std/socketstream.d
@@ -132,7 +132,7 @@ class SocketStream: Stream
          * Does not return the entire stream because that would
          * require the remote connection to be closed.
          */
-        override string toString()
+        override string toString() const
         {
             return sock.toString();
         }
diff --git a/std/utf.d b/std/utf.d
index 0f34e447b9f..5fd785c4e27 100644
--- a/std/utf.d
+++ b/std/utf.d
@@ -72,7 +72,7 @@ class UTFException : Exception
     }
 
 
-    override string toString()
+    override string toString() const
     {
         import std.string;
         if(len == 0)
diff --git a/std/xml.d b/std/xml.d
index d0587bcd965..135cff794ed 100644
--- a/std/xml.d
+++ b/std/xml.d
@@ -824,7 +824,7 @@ class Element : Item
      * if (e1 == e2) { }
      * --------------
      */
-    override bool opEquals(const Object o)
+    override const bool opEquals(const Object o)
     {
         const element = toType!(const Element)(o);
         auto len = items.length;
@@ -848,7 +848,7 @@ class Element : Item
      * if (e1 < e2) { }
      * --------------
      */
-    override int opCmp(const Object o)
+    override const int opCmp(const Object o)
     {
         const element = toType!(const Element)(o);
         for (uint i=0; ; ++i)
@@ -867,7 +867,7 @@ class Element : Item
      * You should rarely need to call this function. It exists so that Elements
      * can be used as associative array keys.
      */
-    override hash_t toHash()
+    override const hash_t toHash()
     {
         hash_t hash = tag.toHash();
         foreach(item;items) hash += item.toHash();
@@ -1233,7 +1233,7 @@ class Comment : Item
      * if (item1 == item2) { }
      * --------------
      */
-    override bool opEquals(const Object o)
+    override const bool opEquals(const Object o)
     {
         const item = toType!(const Item)(o);
         const t = cast(Comment)item;
@@ -1252,7 +1252,7 @@ class Comment : Item
      * if (item1 < item2) { }
      * --------------
      */
-    override int opCmp(const Object o)
+    override const int opCmp(const Object o)
     {
         const item = toType!(const Item)(o);
         const t = cast(Comment)item;
@@ -1266,7 +1266,7 @@ class Comment : Item
      * You should rarely need to call this function. It exists so that Comments
      * can be used as associative array keys.
      */
-    override hash_t toHash() { return hash(content); }
+    override const hash_t toHash() { return hash(content); }
 
     /**
      * Returns a string representation of this comment
@@ -1312,7 +1312,7 @@ class CData : Item
      * if (item1 == item2) { }
      * --------------
      */
-    override bool opEquals(const Object o)
+    override const bool opEquals(const Object o)
     {
         const item = toType!(const Item)(o);
         const t = cast(CData)item;
@@ -1331,7 +1331,7 @@ class CData : Item
      * if (item1 < item2) { }
      * --------------
      */
-    override int opCmp(const Object o)
+    override const int opCmp(const Object o)
     {
         const item = toType!(const Item)(o);
         const t = cast(CData)item;
@@ -1345,7 +1345,7 @@ class CData : Item
      * You should rarely need to call this function. It exists so that CDatas
      * can be used as associative array keys.
      */
-    override hash_t toHash() { return hash(content); }
+    override const hash_t toHash() { return hash(content); }
 
     /**
      * Returns a string representation of this CData section
@@ -1389,7 +1389,7 @@ class Text : Item
      * if (item1 == item2) { }
      * --------------
      */
-    override bool opEquals(const Object o)
+    override const bool opEquals(const Object o)
     {
         const item = toType!(const Item)(o);
         const t = cast(Text)item;
@@ -1408,7 +1408,7 @@ class Text : Item
      * if (item1 < item2) { }
      * --------------
      */
-    override int opCmp(const Object o)
+    override const int opCmp(const Object o)
     {
         const item = toType!(const Item)(o);
         const t = cast(Text)item;
@@ -1422,7 +1422,7 @@ class Text : Item
      * You should rarely need to call this function. It exists so that Texts
      * can be used as associative array keys.
      */
-    override hash_t toHash() { return hash(content); }
+    override const hash_t toHash() { return hash(content); }
 
     /**
      * Returns a string representation of this Text section
@@ -1471,7 +1471,7 @@ class XMLInstruction : Item
      * if (item1 == item2) { }
      * --------------
      */
-    override bool opEquals(const Object o)
+    override const bool opEquals(const Object o)
     {
         const item = toType!(const Item)(o);
         const t = cast(XMLInstruction)item;
@@ -1490,7 +1490,7 @@ class XMLInstruction : Item
      * if (item1 < item2) { }
      * --------------
      */
-    override int opCmp(const Object o)
+    override const int opCmp(const Object o)
     {
         const item = toType!(const Item)(o);
         const t = cast(XMLInstruction)item;
@@ -1504,7 +1504,7 @@ class XMLInstruction : Item
      * You should rarely need to call this function. It exists so that
      * XmlInstructions can be used as associative array keys.
      */
-    override hash_t toHash() { return hash(content); }
+    override const hash_t toHash() { return hash(content); }
 
     /**
      * Returns a string representation of this XmlInstruction
@@ -1550,7 +1550,7 @@ class ProcessingInstruction : Item
      * if (item1 == item2) { }
      * --------------
      */
-    override bool opEquals(const Object o)
+    override const bool opEquals(const Object o)
     {
         const item = toType!(const Item)(o);
         const t = cast(ProcessingInstruction)item;
@@ -1569,7 +1569,7 @@ class ProcessingInstruction : Item
      * if (item1 < item2) { }
      * --------------
      */
-    override int opCmp(const Object o)
+    override const int opCmp(const Object o)
     {
         const item = toType!(const Item)(o);
         const t = cast(ProcessingInstruction)item;
@@ -1583,7 +1583,7 @@ class ProcessingInstruction : Item
      * You should rarely need to call this function. It exists so that
      * ProcessingInstructions can be used as associative array keys.
      */
-    override hash_t toHash() { return hash(content); }
+    override const hash_t toHash() { return hash(content); }
 
     /**
      * Returns a string representation of this ProcessingInstruction
@@ -1599,13 +1599,13 @@ class ProcessingInstruction : Item
 abstract class Item
 {
     /// Compares with another Item of same type for equality
-    abstract override bool opEquals(const Object o);
+    abstract override const bool opEquals(const Object o);
 
     /// Compares with another Item of same type
-    abstract override int opCmp(const Object o);
+    abstract override const int opCmp(const Object o);
 
     /// Returns the hash of this item
-    abstract override hash_t toHash();
+    abstract override const hash_t toHash();
 
     /// Returns a string representation of this item
     abstract override const string toString();
@@ -2070,7 +2070,7 @@ class ElementParser
     /**
      * Returns that part of the element which has already been parsed
      */
-    const override string toString()
+    override const string toString()
     {
         assert(elementStart.length >= s.length);
         return elementStart[0 .. elementStart.length - s.length];