restore method count after redefinition to hide old definition

Compiler/test/invalidation.jl

@@ -142,8 +142,8 @@ begin
     # this redefinition below should invalidate the cache of `pr48932_callee` but not that of `pr48932_caller`
     pr48932_callee(x) = (print(GLOBAL_BUFFER, x); nothing)
 
-    @test length(Base.methods(pr48932_callee)) == 2
-    @test Base.only(Base.methods(pr48932_callee, Tuple{Any})) === first(Base.methods(pr48932_callee))
+    @test length(Base.methods(pr48932_callee)) == 1
+    @test Base.only(Base.methods(pr48932_callee, Tuple{Any})) === only(Base.methods(pr48932_callee))
     @test isempty(Base.specializations(Base.only(Base.methods(pr48932_callee, Tuple{Any}))))
     let mi = only(Base.specializations(Base.only(Base.methods(pr48932_caller))))
         # Base.method_instance(pr48932_callee, (Any,))

base/runtime_internals.jl

@@ -1348,31 +1348,44 @@ function MethodList(mt::Core.MethodTable)
     return MethodList(ms, mt)
 end
 
+function matches_to_methods(ms::Array{Any,1}, mt::Core.MethodTable, mod)
+    # Lack of specialization => a comprehension triggers too many invalidations via _collect, so collect the methods manually
+    ms = Method[(ms[i]::Core.MethodMatch).method for i in 1:length(ms)]
+    # Remove shadowed methods with identical type signatures
+    prev = nothing
+    filter!(ms) do m
+        l = prev
+        repeated = (l isa Method && m.sig == l.sig)
+        prev = m
+        return !repeated
+    end
+    # Remove methods not part of module (after removing shadowed methods)
+    mod === nothing || filter!(ms) do m
+        return parentmodule(m) ∈ mod
+    end
+    return MethodList(ms, mt)
+end
+
 """
     methods(f, [types], [module])
 
 Return the method table for `f`.
 
 If `types` is specified, return an array of methods whose types match.
 If `module` is specified, return an array of methods defined in that module.
-A list of modules can also be specified as an array.
+A list of modules can also be specified as an array or set.
 
 !!! compat "Julia 1.4"
     At least Julia 1.4 is required for specifying a module.
 
 See also: [`which`](@ref), [`@which`](@ref Main.InteractiveUtils.@which) and [`methodswith`](@ref Main.InteractiveUtils.methodswith).
 """
 function methods(@nospecialize(f), @nospecialize(t),
-                 mod::Union{Tuple{Module},AbstractArray{Module},Nothing}=nothing)
+                 mod::Union{Tuple{Module},AbstractArray{Module},AbstractSet{Module},Nothing}=nothing)
     world = get_world_counter()
     world == typemax(UInt) && error("code reflection cannot be used from generated functions")
-    # Lack of specialization => a comprehension triggers too many invalidations via _collect, so collect the methods manually
-    ms = Method[]
-    for m in _methods(f, t, -1, world)::Vector
-        m = m::Core.MethodMatch
-        (mod === nothing || parentmodule(m.method) ∈ mod) && push!(ms, m.method)
-    end
-    MethodList(ms, typeof(f).name.mt)
+    ms = _methods(f, t, -1, world)::Vector{Any}
+    return matches_to_methods(ms, typeof(f).name.mt, mod)
 end
 methods(@nospecialize(f), @nospecialize(t), mod::Module) = methods(f, t, (mod,))
 
@@ -1382,12 +1395,12 @@ function methods_including_ambiguous(@nospecialize(f), @nospecialize(t))
     world == typemax(UInt) && error("code reflection cannot be used from generated functions")
     min = RefValue{UInt}(typemin(UInt))
     max = RefValue{UInt}(typemax(UInt))
-    ms = _methods_by_ftype(tt, nothing, -1, world, true, min, max, Ptr{Int32}(C_NULL))::Vector
-    return MethodList(Method[(m::Core.MethodMatch).method for m in ms], typeof(f).name.mt)
+    ms = _methods_by_ftype(tt, nothing, -1, world, true, min, max, Ptr{Int32}(C_NULL))::Vector{Any}
+    return matches_to_methods(ms, typeof(f).name.mt, nothing)
 end
 
 function methods(@nospecialize(f),
-                 mod::Union{Module,AbstractArray{Module},Nothing}=nothing)
+                 mod::Union{Module,AbstractArray{Module},AbstractSet{Module},Nothing}=nothing)
     # return all matches
     return methods(f, Tuple{Vararg{Any}}, mod)
 end

test/core.jl

@@ -7691,7 +7691,7 @@ end
 # issue #31696
 foo31696(x::Int8, y::Int8) = 1
 foo31696(x::T, y::T) where {T <: Int8} = 2
-@test length(methods(foo31696)) == 2
+@test length(methods(foo31696)) == 1
 let T1 = Tuple{Int8}, T2 = Tuple{T} where T<:Int8, a = T1[(1,)], b = T2[(1,)]
     b .= a
     @test b[1] == (1,)

test/reflection.jl

@@ -569,7 +569,7 @@ fLargeTable() = 4
 fLargeTable(::Union, ::Union) = "a"
 @test fLargeTable(Union{Int, Missing}, Union{Int, Missing}) == "a"
 fLargeTable(::Union, ::Union) = "b"
-@test length(methods(fLargeTable)) == 206
+@test length(methods(fLargeTable)) == 205
 @test fLargeTable(Union{Int, Missing}, Union{Int, Missing}) == "b"
 
 # issue #15280