fix unreachable on bin op between numeric and undefined

Author: Vexu

src/ir.cpp

@@ -15262,7 +15262,9 @@ static IrInstruction *ir_analyze_bin_op_cmp(IrAnalyze *ira, IrInstructionBinOp *
         case ZigTypeIdInt:
         case ZigTypeIdFloat:
         case ZigTypeIdVector:
-            zig_unreachable(); // handled with the type_is_numeric checks above
+            // one of the operands is undefined, this error will be caught by ir_resolve_const_val
+            operator_allowed = true;
+            break;
 
         case ZigTypeIdBool:
         case ZigTypeIdMetaType:

test/compile_errors.zig

@@ -2,6 +2,14 @@ const tests = @import("tests.zig");
 const builtin = @import("builtin");
 
 pub fn addCases(cases: *tests.CompileErrorContext) void {
+    cases.add("bin op with numeric and undefined",
+        \\pub fn main() void {
+        \\    _ = 2 == undefined;
+        \\}
+    , &[_][]const u8{
+        "tmp.zig:2:14: error: use of undefined value here causes undefined behavior",
+    });
+
     cases.add("slice sentinel mismatch",
         \\fn foo() [:0]u8 {
         \\    var x: []u8 = undefined;