Fix partially_inline for unreachable (#56787)

(cherry picked from commit 9118ea7)

Author: wsmoses

base/meta.jl

@@ -365,10 +365,15 @@ function _partially_inline!(@nospecialize(x), slot_replacements::Vector{Any},
         return x
     end
     if isa(x, Core.ReturnNode)
+       # Unreachable doesn't have val defined
+       if !isdefined(x, :val)
+          return x
+       else
         return Core.ReturnNode(
             _partially_inline!(x.val, slot_replacements, type_signature, static_param_values,
                                slot_offset, statement_offset, boundscheck),
         )
+       end
     end
     if isa(x, Core.GotoIfNot)
         return Core.GotoIfNot(

test/meta.jl

@@ -283,4 +283,9 @@ ci = code_lowered(g, Tuple{Val{true}})[1]
     @test Meta.partially_inline!(copy(ci.code), Any[isdefined_globalref, 1], Tuple{typeof(isdefined_globalref), Int},
                                  [], 0, 0, :propagate)[1] == Expr(:isdefined, GlobalRef(Base, :foo))
 
+    withunreachable(s::String) = sin(s)
+    ci = code_lowered(withunreachable, Tuple{String})[1]
+    ci.code[end] = Core.ReturnNode()
+    @test Meta.partially_inline!(copy(ci.code), Any[withunreachable, "foo"], Tuple{typeof(withunreachable), String},
+                                 [], 0, 0, :propagate)[end] == Core.ReturnNode()
 end