Compiler: walk_to_defs, collect_leaves: specialize for predecessors (#57859)

Should make the code less vulnerable to invalidation.

(cherry picked from commit d9441ac)

Author: nsajko

Compiler/src/ssair/passes.jl

@@ -183,7 +183,7 @@ function find_def_for_use(
 end
 
 function collect_leaves(compact::IncrementalCompact, @nospecialize(val), @nospecialize(typeconstraint), 𝕃ₒ::AbstractLattice,
-                        predecessors = ((@nospecialize(def), compact::IncrementalCompact) -> isa(def, PhiNode) ? def.values : nothing))
+                        predecessors::Pre = ((@nospecialize(def), compact::IncrementalCompact) -> isa(def, PhiNode) ? def.values : nothing)) where {Pre}
     if isa(val, Union{OldSSAValue, SSAValue})
         val, typeconstraint = simple_walk_constraint(compact, val, typeconstraint)
     end
@@ -271,7 +271,7 @@ Starting at `val` walk use-def chains to get all the leaves feeding into this `v
 `predecessors(def, compact)` is a callback which should return the set of possible
 predecessors for a "phi-like" node (PhiNode or Core.ifelse) or `nothing` otherwise.
 """
-function walk_to_defs(compact::IncrementalCompact, @nospecialize(defssa), @nospecialize(typeconstraint), predecessors, 𝕃ₒ::AbstractLattice)
+function walk_to_defs(compact::IncrementalCompact, @nospecialize(defssa), @nospecialize(typeconstraint), predecessors::Pre, 𝕃ₒ::AbstractLattice) where {Pre}
     visited_philikes = AnySSAValue[]
     isa(defssa, AnySSAValue) || return Any[defssa], visited_philikes
     def = compact[defssa][:stmt]