Add ismutabletype

JuliaLang · Oct 3, 2021 · 514f7e9 · 514f7e9
1 parent fe75815
commit 514f7e9
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Showing 2 changed files with 17 additions and 2 deletions.
diff --git a/src/Compat.jl b/src/Compat.jl
@@ -1195,6 +1195,16 @@ if VERSION < v"1.7.0-DEV.793"
     end
 end
 
+if !isdefined(Base, Symbol("ismutabletype"))
+    # Borrowed from julia base
+    export ismutabletype
+    function ismutabletype(@nospecialize(t::Type))
+        t = Base.unwrap_unionall(t)
+        # TODO: what to do for `Union`?
+        return isa(t, DataType) && t.mutable
+    end
+end
+
 # https://github.com/JuliaLang/julia/pull/42125
 if !isdefined(Base, Symbol("@constprop"))
     if isdefined(Base, Symbol("@aggressive_constprop"))

diff --git a/test/runtests.jl b/test/runtests.jl
@@ -1186,7 +1186,7 @@ end
         # Check that the ExceptionStacks contain the expected last exception type:
         @test typeof.(first.(excs_with_bts)) == [DivideError]
         @test typeof.(first.(excs_sans_bts)) == [DivideError]
-        
+
         # Check that the ExceptionStack with backtraces `show`s correctly:
         @test occursin(r"""
         1-element ExceptionStack:
@@ -1277,7 +1277,7 @@ end
             return sum(sincos(a))
         end
     end
-    
+
     @test foo1(42) == foo2(42)
 end
 
@@ -1293,3 +1293,8 @@ end
     @test_throws MethodError convert(Period, Minute(1) + Second(30))
     @test_throws MethodError convert(Dates.FixedPeriod, Minute(1) + Second(30))
 end
+
+@testset "ismutabletype" begin
+    @test ismutabletype(Array)
+    @test !ismutabletype(Tuple)
+end