What Ada has on it are its IDE's, MDD, and testing tools that industry is currently using. With stuff like RV-Match and Astree Analyzer, MISRA-C is probably safer than Rust. Rust needs more tooling to be competitive.
The problem is mostly certification and having a stable spec for the language.
The tooling that is needed is mostly productivity tooling, like better code completion (rust analyzer is now pretty promising after RLS kind of stagnated). And maybe better ways to show code coverage.
The problem for usage in safety critical areas is mostly certification and having a stable spec for the language.
The advantage of Ada and Rust is they're cheaper and faster to get safe code out of. Businesses will like that. I don't know how compiler qualification plays out these days.
Lacking a strict type system, discriminated unions, if-expressions (they exist in C but are often discouraged because of readability concerns), match expressions, macros that are AST members, procedural macros, guaranteed mutability restrictions with the borrow checker, etc. are things that a coding rule and analyzer can't bring into a language like C. Most importantly no module system to keep yourself somewhat isolated from third party code that you have no control over.
Add to that that you have humans checking each violation whether they think it will cause problems. Humans fixing these. And in a lot of cases humans not fixing these. Then you're actually still left with a lot of code that a stricter compiler like Rust or Ada would have rejected in the first place.
Furthermore, there's zero proof that e.g. macros, match or variant types have any impact on code quality. Bringing the module system into this is really grasping at straws.
Lacking a strict type system, discriminated unions, if-expressions (they exist in C but are often discouraged because of readability concerns), match expressions, macros that are AST members, procedural macros, guaranteed mutability restrictions with the borrow checker, etc. are things that a coding rule and analyzer can't bring into a language like C. Most importantly no module system to keep yourself somewhat isolated from third party code that you have no control over.
Add to that that you have humans checking each violation whether they think it will cause problems. Humans fixing these. And in a lot of cases humans not fixing these. Then you're actually still left with a lot of code that à stricter compiler like Rust or Ada would have rejected in the first place.
https://www.adacore.com/books/safe-and-secure-software
SPARK is a subset without pointers that feeds information about the program into solvers that prove absence of common classes of errors like overflows and divide by zero. Inspired by Rust, recent work is adding pointers. Praxis' Correct-by-Construction defaulted on Ada with SPARK saved for most critical stuff, esp safety- or security-enforcing.
Right now, Rust is mainly ahead of Ada on dealing with the pointer safety and better safe concurrency. Ada's Ravenscar aimed for safety but was restrictive. That's my take.
Ada/SPARK wins in almost everything else, it has multiple implementations, proven industrial use since early 80's (first standard was in 1983), IDE tooling, it is a common theme in high security computing conferences, libraries for safety critical domains, and people that know the language.
Naturally it has a price disadvantage for FOSS devs that are allergic to GNAT, given that the remaining Ada compilers are well into the enterprise price range.