Merge pull request #20577 from thewilsonator/pointer-subtract

Make subtracting pointers of different types an error

changelog/dmd.deprecation-pointer-subtract.dd

@@ -0,0 +1,11 @@
+An error is now given for subtracting pointers of different types
+
+The following code now gives errors:
+```
+static assert(cast(void*)8 - cast(int*) 0 == 2L);
+static assert(cast(int*) 8 - cast(void*)0 == 8L);
+void test()
+{
+     auto foo = (ushort*).init - (ubyte*).init;
+}
+```

compiler/src/dmd/expressionsem.d

@@ -12241,12 +12241,10 @@ private extern (C++) final class ExpressionSemanticVisitor : Visitor
 
                 if (!p1.equivalent(p2))
                 {
-                    // Deprecation to remain for at least a year, after which this should be
-                    // changed to an error
                     // See https://github.com/dlang/dmd/pull/7332
-                    deprecation(exp.loc,
-                        "cannot subtract pointers to different types: `%s` and `%s`.",
+                    error(exp.loc, "cannot subtract pointers to different types: `%s` and `%s`.",
                         t1.toChars(), t2.toChars());
+                    return setError();
                 }
 
                 // Need to divide the result by the stride

compiler/test/fail_compilation/test11006.d

@@ -1,11 +1,13 @@
-/* REQUIRED_ARGS: -main -de
- * TEST_OUTPUT:
+/* TEST_OUTPUT:
 ---
-fail_compilation/test11006.d(10): Deprecation: cannot subtract pointers to different types: `void*` and `int*`.
-fail_compilation/test11006.d(10):        while evaluating: `static assert(2L == 2L)`
-fail_compilation/test11006.d(11): Deprecation: cannot subtract pointers to different types: `int*` and `void*`.
-fail_compilation/test11006.d(11):        while evaluating: `static assert(8L == 8L)`
+fail_compilation/test11006.d(11): Error: cannot subtract pointers to different types: `void*` and `int*`.
+fail_compilation/test11006.d(11):        while evaluating: `static assert(cast(void*)8 - cast(int*)0 == 2L)`
+fail_compilation/test11006.d(12): Error: cannot subtract pointers to different types: `int*` and `void*`.
+fail_compilation/test11006.d(12):        while evaluating: `static assert(cast(int*)8 - cast(void*)0 == 8L)`
+fail_compilation/test11006.d(13): Error: cannot subtract pointers to different types: `ushort*` and `ubyte*`.
+fail_compilation/test11006.d(13):        while evaluating: `static assert(null - null == 0)`
 ---
  */
 static assert(cast(void*)8 - cast(int*) 0 == 2L);
 static assert(cast(int*) 8 - cast(void*)0 == 8L);
+static assert((ushort*).init - (ubyte*).init == 0);