Nested calls run before the parse-error guard, so a bad path value reaches the receiver as a zero value

[crhntr]

muxt generate emits a nested call before the guard that checks whether argument parsing failed, so the receiver method runs with a zero value when a path parameter does not parse.

For {{define "GET /article/{id} Show(ctx, Load(ctx, id))"}} and a receiver with Load(ctx context.Context, id int), the generated handler is:

idParsed, err := strconv.Atoi(request.PathValue("id"))
if err != nil {
	td.errList = append(td.errList, err)
	td.errStatusCode = http.StatusBadRequest
}
idPathParam := idParsed
result0, err := receiver.Load(ctx, idPathParam)   // runs with 0
if err != nil {
	td.errList = append(td.errList, err)
	td.errStatusCode = http.StatusInternalServerError
}
...
if len(td.errList) == 0 {                          // guards only the outer call
	td.result = receiver.Show(ctx, result0)
	td.okay = true
}

GET /article/not-an-int therefore calls Load(ctx, 0). Two consequences:

• Application code runs on malformed input with a zero value, which may mean something (a sentinel row, an unscoped query, a write), and costs a backend round trip that should have been refused at parse time.
• When the nested method returns an error for that zero value, the 400 becomes a 500 and the application's error text is appended to the body: status=500 body="ERR:strconv.Atoi: parsing \"not-an-int\": invalid syntax\nno such article".

The same method called at the top level (GET /article/{id} Load(ctx, id)) is generated inside if len(td.errList) == 0 and is never invoked. Only nested calls are emitted unguarded.

internal/generate/routes.go appends nestedCall.DefineStmts(), and DefineStmts forces :=, which is what keeps the call from being wrapped. receiverMethodCall already separates VarDecl, Assign and Check, so a fix can hoist var result0 T, then wrap the assignment and its error check in if len(td.errList) == 0 { ... }, as the top-level call already is. It needs to apply at every nesting level, and the generate snapshots will need rewriting with -update.

Reproduced with binaries built from f7e9368 (main) and from the tip of the PR stack (#146–#153): the generated files are byte-identical apart from the version string, so this is long-standing behavior, not something the stack changed.