Chore: No formatting of the generated Rust file but better indent (#6069

)

### What was changed?
The Rust formatter is usually _crashing_ on generated files on big
codebases.
Since it's hard to pinpoint the cause of the crashing, instead, I change
the default generation indentation to 4 spaces like Rust and deactivate
formatting on generated files.

### How has this been tested?
Existing tests should pass

<small>By submitting this pull request, I confirm that my contribution
is made under the terms of the [MIT
license](https://github.com/dafny-lang/dafny/blob/master/LICENSE.txt).</small>

Makefile

@@ -114,7 +114,7 @@ update-go-module:
 update-runtime-dafny:
 	(cd "${DIR}"; cd Source/DafnyRuntime/DafnyRuntimeDafny; make update-go)
 
-pr-nogeneration: format-dfy format update-runtime-dafny update-cs-module update-rs-module update-go-module update-rs-module
+pr-nogeneration: format-dfy format update-runtime-dafny update-cs-module update-rs-module update-go-module
 
 update-standard-libraries:
 	(cd "${DIR}"; cd Source/DafnyStandardLibraries; make update-binary)

Source/DafnyCore/Backends/Rust/Dafny-compiler-rust-rast.dfy

@@ -12,8 +12,8 @@ module RAST
   // Past that, we use Dafny system tuples (see https://www.reddit.com/r/rust/comments/11gvkda/why_rust_std_only_provides_trait_implementation/)
   const MAX_TUPLE_SIZE := 12
 
-  // Default Indentation
-  const IND := "  "
+  // Default Rust-like indentation
+  const IND := "    "
 
   datatype RASTTopDownVisitor<!T(!new)> =
     RASTTopDownVisitor(

Source/DafnyCore/Backends/Rust/Dafny-compiler-rust.dfy

@@ -4068,6 +4068,7 @@ module {:extern "DCOMP"} DafnyToRustCompiler {
     {
       s := "#![allow(warnings, unconditional_panic)]\n";
       s := s + "#![allow(nonstandard_style)]\n";
+      s := s + "#![cfg_attr(any(), rustfmt::skip)]\n"; // Because Rustfmt crashes on some generated files
 
       var externUseDecls := [];
 

Source/DafnyCore/GeneratedFromDafny/DCOMP.cs

@@ -6764,6 +6764,7 @@ public RAST._IExpr Error(Dafny.ISequence<Dafny.Rune> message, RAST._IExpr defaul
       Dafny.ISequence<Dafny.Rune> s = Dafny.Sequence<Dafny.Rune>.Empty;
       s = Dafny.Sequence<Dafny.Rune>.UnicodeFromString("#![allow(warnings, unconditional_panic)]\n");
       s = Dafny.Sequence<Dafny.Rune>.Concat(s, Dafny.Sequence<Dafny.Rune>.UnicodeFromString("#![allow(nonstandard_style)]\n"));
+      s = Dafny.Sequence<Dafny.Rune>.Concat(s, Dafny.Sequence<Dafny.Rune>.UnicodeFromString("#![cfg_attr(any(), rustfmt::skip)]\n"));
       Dafny.ISequence<RAST._IModDecl> _0_externUseDecls;
       _0_externUseDecls = Dafny.Sequence<RAST._IModDecl>.FromElements();
       BigInteger _hi0 = new BigInteger((externalFiles).Count);

Source/DafnyCore/GeneratedFromDafny/RAST.cs

@@ -174,7 +174,7 @@ public static RAST._IExpr IntoUsize(RAST._IExpr underlying) {
       return (((RAST.__default.dafny__runtime).MSel(Dafny.Sequence<Dafny.Rune>.UnicodeFromString("DafnyUsize"))).FSel(Dafny.Sequence<Dafny.Rune>.UnicodeFromString("into_usize"))).Apply1(underlying);
     }
     public static Dafny.ISequence<Dafny.Rune> IND { get {
-      return Dafny.Sequence<Dafny.Rune>.UnicodeFromString("  ");
+      return Dafny.Sequence<Dafny.Rune>.UnicodeFromString("    ");
     } }
     public static RAST._IType SelfOwned { get {
       return (RAST.Path.create_Self()).AsType();