Add core.eprint

src/builtins/builtins.zig

@@ -34,6 +34,7 @@ const funcs = [_]NameFunc{
     // Utils.
     .{"copy",           copy},
     .{"dump",           zErrFunc(dump)},
+    .{"eprint",         eprint},
     .{"errorReport",    zErrFunc(errorReport)},
     .{"getObjectRc",    zErrFunc(getObjectRc)},
     .{"is",             is},
@@ -526,6 +527,30 @@ pub fn performGC(vm: *cy.VM, _: [*]const Value, _: u8) anyerror!Value {
     return map;
 }
 
+pub fn eprint(vm: *cy.VM, args: [*]const cy.Value, _: u8) Value {
+    const err = eprint_c(vm, args[0]);
+    if (!err.isNull()) {
+        return Value.Interrupt;
+    }
+    return Value.Void;
+}
+
+pub fn eprint_c(ctx: cy.Context, arg: rt.Any) callconv(.C) rt.Error {
+    if (build_options.rt == .vm) {
+        const str = ctx.getOrBufPrintValueStr(&cy.tempBuf, arg) catch |err| {
+            return cy.builtins.prepThrowZError2(ctx, err, @errorReturnTrace());
+        };
+        rt.err(ctx, str);
+        rt.err(ctx, "\n");
+    } else {
+        const str = arg.type.toPrintString(ctx, arg);
+        rt.err(ctx, str.slice());
+        rt.err(ctx, "\n");
+        ctx.release(str.buf);
+    }
+    return rt.Error.initNull();
+}
+
 pub fn print(vm: *cy.VM, args: [*]const cy.Value, _: u8) Value {
     const err = print_c(vm, args[0]);
     if (!err.isNull()) {

src/builtins/builtins_vm.cy

@@ -4,6 +4,9 @@
 --| Prints the result of `toCyon` on a value.
 #host func dump(val any) void
 
+--| Prints a value to the error stream. The host determines how it is printed.
+#host func eprint(str any) void
+
 #host func errorReport() String
 
 --| Returns the current reference count of an object.

test/core/table_access_panic.cy

@@ -4,7 +4,7 @@ o.b
 --cytest: error
 --panic: Field not found in value.
 --
---core:183:16 $get:
+--core:186:16 $get:
 --        return table_data[name]
 --               ^
 --main:2:3 main: