precompile restrict for Gray/RGB (#2)

Author: johnnychen94

src/ImageUtils.jl

@@ -9,4 +9,9 @@ using ImageCore.OffsetArrays
 include("restrict.jl")
 include("compat.jl")
 
+if VERSION >= v"1.4.2" # work around https://github.com/JuliaLang/julia/issues/34121
+    include("precompile.jl")
+    _precompile_()
+end
+
 end

src/precompile.jl

@@ -0,0 +1,19 @@
+macro warnpcfail(ex::Expr)
+    modl = __module__
+    file = __source__.file === nothing ? "?" : String(__source__.file)
+    line = __source__.line
+    quote
+        $(esc(ex)) || @warn """precompile directive
+     $($(Expr(:quote, ex)))
+ failed. Please report an issue in $($modl) (after checking for duplicates) or remove this directive.""" _file=$file _line=$line
+    end
+end
+
+function _precompile_()
+    for ST in (N0f8, Float32, Float64)
+        for T in (Gray{ST}, RGB{ST})
+            @warnpcfail precompile(restrict, (Vector{T},))
+            @warnpcfail precompile(restrict, (Matrix{T},))
+        end
+    end
+end # _precompile_