constrain the path argument of include functions to AbstractString

Each `Module` defined with `module` automatically gets an `include`
function with two methods. Each of those two methods takes a file path
as its last argument. Even though the path argument is unconstrained by
dispatch, it's documented as constrained with `::AbstractString`:

https://docs.julialang.org/en/v1.11-dev/base/base/#include

Furthermore, I think that any invocation of `include` with a
non-`AbstractString` path will necessarily throw a `MethodError`
eventually. Thus this change should be harmless.

Adding the type constraint to the path argument is an improvement
because any possible exception would be thrown earlier than before.

Apart from modules defined with `module`, the same issue is present
with the anonymous modules created by `evalfile`, which is also
addressed.

Sidenote: `evalfile` seems to be completely untested apart from the
test added here.

base/loading.jl

@@ -2715,8 +2715,8 @@ function evalfile(path::AbstractString, args::Vector{String}=String[])
         Expr(:toplevel,
              :(const ARGS = $args),
              :(eval(x) = $(Expr(:core, :eval))(__anon__, x)),
-             :(include(x) = $(Expr(:top, :include))(__anon__, x)),
-             :(include(mapexpr::Function, x) = $(Expr(:top, :include))(mapexpr, __anon__, x)),
+             :(include(x::AbstractString) = $(Expr(:top, :include))(__anon__, x)),
+             :(include(mapexpr::Function, x::AbstractString) = $(Expr(:top, :include))(mapexpr, __anon__, x)),
              :(include($path))))
 end
 evalfile(path::AbstractString, args::Vector) = evalfile(path, String[args...])

src/jlfrontend.scm

@@ -211,11 +211,11 @@
           (block
            ,@loc
            (call (core eval) ,name ,x)))
-       (= (call include ,x)
+       (= (call include (:: ,x (top AbstractString)))
           (block
            ,@loc
            (call (core _call_latest) (top include) ,name ,x)))
-       (= (call include (:: ,mex (top Function)) ,x)
+       (= (call include (:: ,mex (top Function)) (:: ,x (top AbstractString)))
           (block
            ,@loc
            (call (core _call_latest) (top include) ,mex ,name ,x)))))

test/loading.jl

@@ -793,6 +793,17 @@ import .Foo28190.Libdl; import Libdl
     end
 end
 
+@testset "`::AbstractString` constraint on the path argument to `include`" begin
+    for m ∈ (NotPkgModule, evalfile("testhelpers/just_module.jl"))
+        let i = m.include
+            @test !applicable(i, (nothing,))
+            @test !applicable(i, (identity, nothing,))
+            @test !hasmethod(i, Tuple{Nothing})
+            @test !hasmethod(i, Tuple{Function,Nothing})
+        end
+    end
+end
+
 @testset "`Base.project_names` and friends" begin
     # Some functions in Pkg assumes that these tuples have the same length
     n = length(Base.project_names)

test/testhelpers/just_module.jl

@@ -0,0 +1 @@
+@__MODULE__