Formatter did not properly handle "null" for any, and null for empty faults. #2375

lib/std/io/formatter.c3

@@ -146,10 +146,12 @@ fn usz? Formatter.out_str(&self, any arg) @private
 		case VOID:
 			return self.out_substr("void");
 		case FAULT:
-			return self.out_substr((*(fault*)arg.ptr).nameof);
+			fault f = *(fault*)arg.ptr;
+			return self.out_substr(f ? f.nameof : "(nofault)");
 		case INTERFACE:
 		case ANY:
-			return self.out_str(*(any*)arg);
+			any a = *(any*)arg;
+			return a ? self.out_str(a) : self.out_substr("(null)");
 		case OPTIONAL:
 			unreachable();
 		case SIGNED_INT:

releasenotes.md

@@ -20,6 +20,7 @@
 - Parsing difference between "0x00." and "0X00." literals #2371
 - Fixed bug generating `$c += 1` when `$c` was derived from a pointer but behind a cast.
 - Compiler segfault when using bitwise not on number literal cast to bitstruct #2373.
+- Formatter did not properly handle "null" for any, and null for empty faults. #2375
 
 ### Stdlib changes
 - Add `==` to `Pair`, `Triple` and TzDateTime. Add print to `Pair` and `Triple`.

test/unit/regression/formatting.c3

@@ -0,0 +1,30 @@
+module format_test;
+import std::io;
+
+interface Decl
+{
+}
+
+struct TestS (Decl, Printable)
+{
+    int a;
+}
+fn usz? TestS.to_format(&self, Formatter* formatter) @dynamic => formatter.printf("[%d]", self.a);
+
+faultdef DERP;
+
+fn void various_cornercases() @test
+{
+    TestS a = {100};
+    Decl z = &a;
+    test::eq(string::tformat("%s", z), "[100]");
+
+    fault p; fault o = DERP;
+    test::eq(string::tformat("%s|%s", p, o), "(nofault)|format_test::DERP");
+
+    Decl y;
+    test::eq(string::tformat("%s", y), "(null)");
+
+    int* x;
+    test::eq(string::tformat("%s", x), "0x0");
+}