[Demangle][Rust] Parse dyn-bounds

[tmiasko]

Summary

Depends on D102729

[dblaikie]

Could you split this up - one patch to add dyn-bounds with zero dyn-traits, then add dyn-traits with zero dyn-trait-assoc-binding, then add those? (takes me a while to check the test cases/understand exactly what they're doing - so having really narrow patches makes it easier to focus on the difference between one patch and the next)

[tmiasko]

Parse dyn-bounds without any dyn-traits

At language level at least one trait is required, so visually this doesn't look
quite right without any traits and trailing whitespace at the end.

[dblaikie]

llvm/lib/Demangle/RustDemangle.cpp

485–492

keep thinking it'd be nice if this were wrapped up in some (albeit parameterized for different situations you mentioned) "demangleLifetime" to match the syntax description more closely

555

According to the grammar/spec this is <binder> = "G" <base-62-number> rather than <binder> = ["G" <base-62-number>]?

556

Not sure how consistently this is done throughout the code - but maybe including "optional" when a feature is optional (so it's clear it's implementing [<binder>] not <binder>) would be good?

llvm/test/Demangle/rust.test

243–244

Could this test be simplified down to:

CHECK: trait::<dyn for<'b> + 'a>
       _RIC5traitDG_EL_E

[tmiasko]

Rebase

llvm/lib/Demangle/RustDemangle.cpp

485–492

I am still somewhat reluctant to change this, since I would have to introduce three different variants and each would be used only once. For example, in variant here, when lifetime is printed it should be preceded by + .

556

I renamed the function in parent revision to demangleOptionalBinder.

llvm/test/Demangle/rust.test

243–244

In "D" <dyn-bounds> <lifetime> production, <lifetime> is outside the binder from <dyn-bounds>. Additionally since erased lifetimes are not printed here, test has to use another binder.

[dblaikie]

Looks good - thanks for walking me through it!

llvm/include/llvm/Demangle/RustDemangle.h

public:
   bool demangle(StringView MangledName);
 
 private:
   void demanglePath(InType InType);
   void demangleImplPath(InType InType);
   void demangleGenericArg();
   void demangleType();
   void demangleFnSig();
+  void demangleDynBounds();
   void demangleBinder();
   void demangleConst();
   void demangleConstInt();
   void demangleConstBool();
   void demangleConstChar();
 
   Identifier parseIdentifier();
   uint64_t parseOptionalBase62Number(char Tag);

llvm/lib/Demangle/RustDemangle.cpp

case 'P':
     break;
   case 'O':
     print("*mut ");
     demangleType();
     break;
   case 'F':
     demangleFnSig();
     break;
+  case 'D':
+    demangleDynBounds();
+    if (consumeIf('L')) {
+      if (auto Lifetime = parseBase62Number()) {
+        print(" + ");
+        printLifetime(Lifetime);
+      }
+    } else {
+      Error = true;
+    }
+    break;
   default:
     Position = Start;
     demanglePath(rust_demangle::InType::Yes);
     break;
   }
 }
 
 // <fn-sig> := [<binder>] ["U"] ["K" <abi>] {<type>} "E" <type>
void Demangler::demangleFnSig() {
   if (consumeIf('u')) {
     // Skip the unit type from the output.
   } else {
     print(" -> ");
     demangleType();
   }
 }
 
+// <dyn-bounds> = [<binder>] {<dyn-trait>} "E"
+void Demangler::demangleDynBounds() {
+  SwapAndRestore<size_t> SaveBoundLifetimes(BoundLifetimes, BoundLifetimes);
+  print("dyn ");
+  demangleBinder();
+  // FIXME demangle {dyn-trait}
+  if (!consumeIf('E'))
+    Error = true;
+}
+
 // Demangles optional binder and updates the number of bound lifetimes.
 //
 // <binder> = ["G" <base-62-number>]
 void Demangler::demangleBinder() {
   uint64_t Binder = parseOptionalBase62Number('G');
   if (Error || Binder == 0)
     return;
 
   // In valid inputs each bound lifetime is referenced later. Referencing a
   // lifetime requires at least one byte of input. Reject inputs that are too
   // short to reference all bound lifetimes. Otherwise demangling of invalid
   // binders could generate excessive amounts of output.

llvm/test/Demangle/rust.test

CHECK: function::<extern "C" fn()>
        _RIC8functionFKCEuE
 
 CHECK: function::<extern "cdecl" fn()>
        _RIC8functionFK5cdeclEuE
 
 CHECK: function::<unsafe extern "C-cmse-nonsecure-call" fn()>
        _RIC8functionFUK21C_cmse_nonsecure_callEuE
 
+; Trait objects
+
+CHECK: trait::<dyn >
+       _RIC5traitDEL_E
+
+CHECK: trait::<dyn for<'a> >
+       _RIC5traitDG_EL_E
+
+CHECK: trait::<for<'a> fn(dyn for<'b> + 'a)>
+       _RIC5traitFG_DG_EL0_EuE
+
+; Invalid trait object, missing lifetime.
+
+CHECK: _RIC5traitDEE
+       _RIC5traitDEE
+
 ; Binders
 
 CHECK: binders::<for<'a> fn(&'a _)>
        _RIC7bindersFG_RL0_pEuE
 
 CHECK: binders::<for<'a> fn(&'a mut _)>
        _RIC7bindersFG_QL0_pEuE