From 8035991ac3e8433517b353fe755d4360db549df0 Mon Sep 17 00:00:00 2001
From: Christoffer Lerno <christoffer@aegik.com>
Date: Wed, 10 Sep 2025 10:47:14 +0200
Subject: [PATCH] `??` with void results on both sides cause a compiler crash
 #2472

---
 releasenotes.md                           |  1 +
 src/compiler/llvm_codegen_expr.c          |  8 ++++
 test/test_suite/errors/else_with_void.c3t | 54 +++++++++++++++++++++++
 3 files changed, 63 insertions(+)
 create mode 100644 test/test_suite/errors/else_with_void.c3t

diff --git a/releasenotes.md b/releasenotes.md
index b6d575d7e..68ad582d3 100644
--- a/releasenotes.md
+++ b/releasenotes.md
@@ -19,6 +19,7 @@
 - Any register allowed in X86_64 inline asm address. #2463
 - int val = some_int + some_distinct_inline_int errors that int cannot be cast to DistinctInt #2468
 - Compiler hang with unaligned load-store pair. #2470
+- `??` with void results on both sides cause a compiler crash #2472.
 
 ### Stdlib changes
 - Added generic `InterfaceList` to store a list of values that implement a specific interface
diff --git a/src/compiler/llvm_codegen_expr.c b/src/compiler/llvm_codegen_expr.c
index 4db1d1a1c..ad1bcd551 100644
--- a/src/compiler/llvm_codegen_expr.c
+++ b/src/compiler/llvm_codegen_expr.c
@@ -3907,6 +3907,14 @@ static void llvm_emit_else(GenContext *c, BEValue *be_value, Expr *expr)
 
 	assert(success_end_block && else_block_exit);
 
+	// We might have a void here
+	if (!real_value.value)
+	{
+		assert(type_flatten(expr->type) == type_void);
+		assert(!else_value.value);
+		llvm_value_set(be_value, NULL, type_void);
+		return;
+	}
 	// Emit an address if the phi is was by address
 	if (was_address)
 	{
diff --git a/test/test_suite/errors/else_with_void.c3t b/test/test_suite/errors/else_with_void.c3t
new file mode 100644
index 000000000..881830ed8
--- /dev/null
+++ b/test/test_suite/errors/else_with_void.c3t
@@ -0,0 +1,54 @@
+// #target: macos-x64
+module func_point_test;
+import std::io;
+import std::collections;
+
+alias FuncPoint = fn void(String text);
+
+fn void test(String text = "test123")
+{
+	io::printn(text);
+}
+
+fn void main()
+{
+	HashMap{String, FuncPoint} map;
+	map.tinit();
+	map.set("test", &test);
+
+	String test_index = "index";
+
+	map[test_index]("Hello World") ?? test();
+}
+
+/* #expect: func_point_test.ll
+
+define void @func_point_test.main() #0 {
+entry:
+  %map = alloca %HashMap, align 8
+  %test_index = alloca %"char[]", align 8
+  %retparam = alloca ptr, align 8
+  call void @llvm.memset.p0.i64(ptr align 8 %map, i8 0, i64 48, i1 false)
+  %0 = call ptr @"std_collections_map$String$fn$void$String$$.HashMap.tinit"(ptr %map, i32 16, float 7.500000e-01)
+  %1 = call i8 @"std_collections_map$String$fn$void$String$$.HashMap.set"(ptr %map, ptr @.str, i64 4, ptr @func_point_test.test)
+  store %"char[]" { ptr @.str.1, i64 5 }, ptr %test_index, align 8
+  %lo = load ptr, ptr %test_index, align 8
+  %ptradd = getelementptr inbounds i8, ptr %test_index, i64 8
+  %hi = load i64, ptr %ptradd, align 8
+  %2 = call i64 @"std_collections_map$String$fn$void$String$$.HashMap.get"(ptr %retparam, ptr %map, ptr %lo, i64 %hi)
+  %not_err = icmp eq i64 %2, 0
+  %3 = call i1 @llvm.expect.i1(i1 %not_err, i1 true)
+  br i1 %3, label %after_check, label %else_block
+
+after_check:                                      ; preds = %entry
+  %4 = load ptr, ptr %retparam, align 8
+  call void %4(ptr @.str.2, i64 11)
+  br label %phi_block
+
+else_block:                                       ; preds = %entry
+  call void @func_point_test.test(ptr @.str.3, i64 7)
+  br label %phi_block
+
+phi_block:                                        ; preds = %else_block, %after_check
+  ret void
+}