make -pattern equivalent to not(pattern) when possible

Author: rfourquet

src/patterns.jl

@@ -169,9 +169,17 @@ if and only if it doesn't match `pattern`.
 
 For example `not("a")` matches any testset whose subject doesn't contain `"a"`,
 and `not(1:3)` matches all the testsets but the first three of a module.
+
+If `pattern` is an integer or a `ReTest` object (i.e. not a `AbstractString`,
+`Regex`, `Tuple` or `AbstractArray`), `not(pattern)` can be expressed as `-pattern`.
+
+`String` patterns can also be negated by prepending `'-'`, see [`retest`](@ref)
+for details.
 """
 not(x) = Not(make_pattern(x))
 
+Base.:-(x::Pattern) = not(x)
+
 
 """
     interpolated

test/test_patterns.jl

@@ -1,14 +1,17 @@
 module TestPatterns
 using Test
 
-using ReTest: and, or, not, interpolated, reachable
+using ReTest: and, or, not, interpolated, reachable, depth
 
 @testset "patterns: ==" begin
-    basics = [and(), or(), not(0), interpolated, 0, r""]
+    basics = [and(), or(), not(0), interpolated, 0, r"", depth(2)]
     VERSION >= v"1.3" && push!(basics, reachable(1))
     for a = basics, b = basics
         if a === b
             @test a == b
+            if !(a isa Regex || a isa Integer)
+                @test -a == not(a)
+            end
         else
             @test a != b
             for f in (and, or)
@@ -39,4 +42,12 @@ using ReTest: and, or, not, interpolated, reachable
     end
 end
 
+@testset "patterns: not" begin
+    pats = [or(1, 3), and(1, r"a"), not(1), interpolated, depth(3)]
+    VERSION >= v"1.3" && push!(pats, reachable("c"))
+    for p ∈ pats
+        @test -p == not(p)
+    end
+end
+
 end # TestPatterns