refactor: minor type-stability improvements

Author: AayushSabharwal

lib/ModelingToolkitBase/src/systems/index_cache.jl

@@ -644,14 +644,20 @@ function reorder_parameters(ic::IndexCache, ps::Vector{SymbolicT}; drop_missing
             if i isa Int
                 param_buf[i] = p
             else
-                param_buf[i] = collect(p)
+                i = (first(i)::Int):(last(i)::Int)
+                for (buf_i, p_i) in zip(i, SU.stable_eachindex(p))
+                    param_buf[buf_i] = p[p_i]
+                end
             end
         elseif haskey(ic.initials_idx, p)
             i = ic.initials_idx[p]
             if i isa Int
                 initials_buf[i] = p
             else
-                initials_buf[i] = collect(p)
+                i = (first(i)::Int):(last(i)::Int)
+                for (buf_i, p_i) in zip(i, SU.stable_eachindex(p))
+                    initials_buf[buf_i] = p[p_i]
+                end
             end
         elseif haskey(ic.constant_idx, p)
             i, j = ic.constant_idx[p]

lib/ModelingToolkitBase/src/systems/system.jl

@@ -1176,7 +1176,7 @@ end
 
 Get the metadata associated with key `k` in system `sys` or `default` if it does not exist.
 """
-function SymbolicUtils.getmetadata(sys::AbstractSystem, k::DataType, default)
+function SymbolicUtils.getmetadata(sys::AbstractSystem, @nospecialize(k::DataType), default)
     meta = get_metadata(sys)
     return get(meta, k, default)
 end
@@ -1188,7 +1188,7 @@ Set the metadata associated with key `k` in system `sys` to value `v`. This is a
 out-of-place operation, and will return a shallow copy of `sys` with the appropriate
 metadata values.
 """
-function SymbolicUtils.setmetadata(sys::AbstractSystem, k::DataType, v)
+function SymbolicUtils.setmetadata(sys::AbstractSystem, @nospecialize(k::DataType), @nospecialize(v))
     meta = get_metadata(sys)
     meta = Base.ImmutableDict(meta, k => v)::MetadataT
     return @set sys.metadata = meta