require opEquals for AA keys

- Check that the compiler can generate a runtime function to test AA keys for equality.

- This is necessary to switch the druntime implementation from opCmp to opEquals.

src/mtype.c

@@ -4684,13 +4684,23 @@ printf("index->ito->ito = x%x\n", index->ito->ito);
             return Type::terror;
         case Tstruct:
         {
-            /* AA's need opCmp. Issue error if not correctly set up.
+            /* AA's need opEquals and opCmp. Issue error if not correctly set up.
              */
             StructDeclaration *sd = ((TypeStruct *)index->toBasetype())->sym;
             if (sd->scope)
                 sd->semantic(NULL);
 
             // duplicate a part of StructDeclaration::semanticTypeInfoMembers
+            if (sd->xeq &&
+                sd->xeq->scope &&
+                sd->xeq->semanticRun < PASSsemantic3done)
+            {
+                unsigned errors = global.startGagging();
+                sd->xeq->semantic3(sd->xeq->scope);
+                if (global.endGagging(errors))
+                    sd->xeq = sd->xerreq;
+            }
+
             if (sd->xcmp &&
                 sd->xcmp->scope &&
                 sd->xcmp->semanticRun < PASSsemantic3done)
@@ -4701,6 +4711,13 @@ printf("index->ito->ito = x%x\n", index->ito->ito);
                     sd->xcmp = sd->xerrcmp;
             }
 
+            if (sd->xeq == sd->xerreq)
+            {
+                error(loc, "associative array key type %s does not have 'const bool opEquals(ref const %s)' member function",
+                        index->toBasetype()->toChars(), sd->toChars());
+                return Type::terror;
+            }
+            // the opCmp requirement can go away once druntime fully switched to using opEquals
             if (sd->xcmp == sd->xerrcmp)
             {
                 error(loc, "associative array key type %s does not have 'const int opCmp(ref const %s)' member function",

test/fail_compilation/fail11591b.d

@@ -0,0 +1,34 @@
+/*
+TEST_OUTPUT:
+---
+fail_compilation/fail11591b.d(16): Error: associative array key type S11591 does not have 'const bool opEquals(ref const S11591)' member function
+---
+*/
+
+struct S11591
+{
+    bool opEquals(int i) { return false; }
+    Object o; // needed to suppress compiler generated opEquals
+}
+
+void test11591()
+{
+    int[S11591] aa;
+}
+
+/*
+TEST_OUTPUT:
+---
+fail_compilation/fail11591b.d(30): Error: associative array key type S12307a does not have 'const bool opEquals(ref const S12307a)' member function
+fail_compilation/fail11591b.d(31): Error: associative array key type S12307b does not have 'const bool opEquals(ref const S12307b)' member function
+---
+*/
+struct S12307a { bool opEquals(T : typeof(this))(T) { return false; } }
+
+void test12307()
+{
+    int[S12307a] aa1;    // a
+    int[S12307b] aa2;    // b
+}
+
+struct S12307b { bool opEquals(T : typeof(this))(T) { return false; } }

test/runnable/imports/link12144a.d

@@ -9,7 +9,7 @@ struct S8 { bool opEquals(T : typeof(this))(T) { return false; } }
 struct S9 { bool opEquals(T : typeof(this))(T) { return false; } }
 
 struct S10 { bool opEquals(T : typeof(this))(T) { return false; } }
-struct S11 { bool opEquals(T : typeof(this))(T) { return false; }
+struct S11 { bool opEquals(T : typeof(this))(T) const { return false; }
              int opCmp(T : typeof(this))(T) const { return 0; } }
 struct S12 { bool opEquals(T : typeof(this))(T) { return false; } }
 struct S13 { bool opEquals(T : typeof(this))(T) { return false; } }