introduce MLStyle.enum_matcher

Author: thautwarm

Project.toml

@@ -1,7 +1,7 @@
 name = "MLStyle"
 uuid = "d8e11817-5142-5d16-987a-aa16d5891078"
 authors = ["thautwarm <twshere@outlook.com>"]
-version = "0.4.16"
+version = "0.4.17"
 
 [deps]
 

docs/syntax/pattern.md

@@ -350,24 +350,28 @@ You can extend following APIs for your pattern objects, to implement custom patt
     `MLStyle.pattern_unref(pat_obj, expr_to_pat, [:a, :b]`.
 
 - `MLStyle.is_enum`
-  
+
    In a pattern `[A, B]`, usually we think both `A` and `B` are capturing patterns. However, it is handy if we can have a pattern `A` whose match means comparing to the global variable `A`.
 
    To achieve this, we provide `MLStyle.is_enum`.
    For a visible global variable `A`, if `MLStyle.is_enum(A) == true`, a symbol `A` will compile into a pattern with `MLStyle.pattern_uncall(A, expr_to_ast, [], [], [])`.
 
+- `MLStyle.enum_matcher(E, value_to_match)`:
+
+    If `MLStyle.is_enum(E) == true`, we will call `MLStyle.enum_matcher(E, value_to_match)` to compile `E` into a pattern.
+
 We present some examples for understandability:
 
 ### Support Pattern Matching for Julia Enums
 
 ```julia-console
 julia> using MLStyle
-julia> using MLStyle.AbstractPatterns: literal
 julia> @enum E E1 E2
 # mark E1, E2 as non-capturing patterns
 julia> MLStyle.is_enum(::E) = true
-# tell the compiler how to match E1, E2
-julia> MLStyle.pattern_uncall(e::E, _, _, _, _) = literal(e)
+# tell the compiler how to match E1 and E2
+# NOTE: make sure it evaluates to a boolean value!
+julia> MLStyle.enum_matcher(e::E, expr) = :($e === $expr)
 julia> x = E2
 julia> @match x begin
            E1 => "match E1!"
@@ -383,13 +387,13 @@ julia> @macroexpand @match x begin
 :(let
       var"##return#261" = nothing
       var"##263" = x
-      if var"##263" === E1
+      if E1 === var"##263"
           var"##return#261" = let
                   "match E1!"
               end
           $(Expr(:symbolicgoto, Symbol("####final#262#264")))
       end
-      if var"##263" === E2
+      if E1 === var"##263"
           var"##return#261" = let
                   "match E2!"
               end

src/MatchImpl.jl

@@ -5,7 +5,19 @@ if isdefined(Base, :Experimental) && isdefined(Base.Experimental, Symbol("@compi
 end
 
 export is_enum,
-    pattern_uncall, pattern_unref, pattern_unmacrocall, @switch, @case, @tryswitch, @match, @trymatch, Where, gen_match, gen_switch
+       enum_matcher,
+       pattern_uncall,
+       pattern_unref,
+       pattern_unmacrocall,
+       @switch,
+       @case,
+       @tryswitch,
+       @match,
+       @trymatch,
+       Where,
+       gen_match,
+       gen_switch
+
 export Q
 import MLStyle
 using MLStyle: mlstyle_report_deprecation_msg!
@@ -17,8 +29,70 @@ using MLStyle.AbstractPatterns
 using MLStyle.AbstractPatterns.BasicPatterns
 OptionalLn = Union{LineNumberNode, Nothing}
 
+"""
+    is_enum(EnumPattern)::Bool
+
+Convert the pattern `EnumPattern` to `EnumPattern()`.
+
+e.g.,
+    ```
+    abstract type AbsS end
+    struct S1 <: AbsS end
+    struct S2 <: AbsS end
+    MLStyle.pattern_uncall(::Type{S}, self, _, _, _) where {S<:AbsS} = literal(S())
+    MLStyle.is_enum(::Type{<:AbsS}) = true
+
+    x = S1()
+    @match x begin
+        S2 => 1
+        S1 => 2
+    end
+    ```
+
+"""
 is_enum(_)::Bool = false
-function pattern_uncall end
+
+"""
+    enum_matcher(Enum, value)::Expr
+
+Generates the expression used to test if `value` is the case `Enum`.
+
+NOTE that this only works when `is_enum(Enum)` is `true`!!!
+
+    @match V begin
+        Enum => ...
+    @end
+
+Above single case matches when
+
+1. `enum_matcher(Enum, ::Any)` is not defined and `V == Enum`.
+2. The expression generated from `enum_matcher(Enum, :V)`
+   evaluates to `true` under the current module.
+
+"""
+function enum_matcher end
+
+struct _EnumCase{E}
+    pattern::E
+end
+
+function pattern_uncall(enumCase::_EnumCase{E}, self, type_params, type_args, args) where E
+    isempty(type_params) || error("Enum type should not have type parameters!")
+    isempty(type_args) || error("Enum type should not have type arguments!")
+    isempty(args) || error("Enum type should not have arguments!")
+
+    let enumPattern = enumCase.pattern
+        if hasmethod(MLStyle.enum_matcher, Tuple{E, Any})
+            function via_enum_matcher(target, _, _)
+                return MLStyle.enum_matcher(enumPattern, target)
+            end
+            guard(via_enum_matcher)
+        else
+            pattern_uncall(enumPattern, self, type_params, type_args, args)
+        end
+    end
+end
+
 function pattern_unref end
 function pattern_unmacrocall(macro_func, self::Function, args::AbstractArray)
     @sswitch args begin
@@ -85,6 +159,12 @@ function guess_type_from_expr(m::Module, ex::Any, tps::Set{Symbol})
     end
 end
 
+struct ModuleBoundedEx2tf <: Function
+    m::Module
+end
+
+@inline (self::ModuleBoundedEx2tf)(arg) = ex2tf(self.m, arg)
+
 ex2tf(m::Module, @nospecialize(a)) = literal(a)
 ex2tf(m::Module, l::LineNumberNode) = wildcard
 ex2tf(m::Module, q::QuoteNode) = literal(q.value)
@@ -97,8 +177,8 @@ ex2tf(m::Module, n::Symbol) =
     else
         if isdefined(m, n)
             p = getfield(m, n)
-            rec(x) = ex2tf(m, x)
-            is_enum(p) && return pattern_uncall(p, rec, [], [], [])
+            rec = ModuleBoundedEx2tf(m)
+            is_enum(p) && return pattern_uncall(_EnumCase(p), rec, [], [], [])
         end
         P_capture(n)
     end
@@ -112,7 +192,8 @@ function ex2tf(m::Module, s::QuotePattern)
 end
 
 function ex2tf(m::Module, w::Where)
-    rec(x) = ex2tf(m, x)
+    rec = ModuleBoundedEx2tf(m)
+
     @sswitch w begin
         @case Where(; value = val, type = t, type_parameters = tps)
 
@@ -170,7 +251,7 @@ end
 
 function ex2tf(m::Module, ex::Expr)
     eval = m.eval
-    rec(x) = ex2tf(m, x)
+    rec = ModuleBoundedEx2tf(m)
 
     @sswitch ex begin
         @case Expr(:||, args)

test/issues/154.jl

@@ -0,0 +1,63 @@
+using MLStyle
+import MLStyle.AbstractPatterns
+
+abstract type Enum154 end
+
+struct Enum154_1_Cons <: Enum154 end
+
+struct Enum154_2_Cons <: Enum154
+    x::Vector{Int}
+end
+MLStyle.@as_record Enum154_2_Cons
+
+MLStyle.is_enum(::Enum154) = true
+MLStyle.enum_matcher(enum::Enum154, expr) = :($enum === $expr)
+
+const Enum154_1 = Enum154_1_Cons()
+
+function Base.:(==)(a::Enum154, b::Enum154)
+    @match (a, b) begin
+        (Enum154_1, Enum154_1) => true
+        (Enum154_2_Cons(xs), Enum154_2_Cons(ys)) => xs == ys
+        _ => false
+    end
+end
+
+# traditional behaviour
+
+@enum JuliaEnum_154 begin
+    JuliaEnum_154_a
+    JuliaEnum_154_b
+    JuliaEnum_154_c
+end
+
+MLStyle.is_enum(::JuliaEnum_154) = true
+
+MLStyle.pattern_uncall(a::JuliaEnum_154, ::Vararg) = MLStyle.AbstractPatterns.literal(a)
+
+function eq_154(a, b)
+    @match (a, b) begin
+        (JuliaEnum_154_a, JuliaEnum_154_a) => true
+        (JuliaEnum_154_b, JuliaEnum_154_b) => true
+        (JuliaEnum_154_c, JuliaEnum_154_c) => true
+        _ => false
+    end
+end
+
+@testset "issue 154" begin
+    @testset "tag matching support" begin
+        @test Enum154_1 == Enum154_1
+        @test Enum154_2_Cons([1, 2, 3]) == Enum154_2_Cons([1, 2, 3])
+        @test Enum154_2_Cons([1, 2, 3]) != Enum154_2_Cons([1, 2, 4])
+        @test Enum154_1 != Enum154_2_Cons([1, 2, 3])
+    end
+
+    @testset "traditional" begin
+        @test eq_154(JuliaEnum_154_a, JuliaEnum_154_a)
+        @test eq_154(JuliaEnum_154_b, JuliaEnum_154_b)
+        @test eq_154(JuliaEnum_154_c, JuliaEnum_154_c)
+        @test !eq_154(JuliaEnum_154_a, JuliaEnum_154_b)
+        @test !eq_154(JuliaEnum_154_b, JuliaEnum_154_c)
+        @test !eq_154(JuliaEnum_154_c, JuliaEnum_154_a)
+    end
+end

test/runtests.jl

@@ -52,7 +52,6 @@ MODULE = TestModule
 
 @use GADT
 
-include("issues/109.jl")
 include("when.jl")
 include("switch.jl")
 include("untyped_lam.jl")
@@ -80,5 +79,7 @@ include("MQuery/test.jl")
 
 include("issues/87.jl")
 include("issues/62.jl")
+include("issues/109.jl")
+include("issues/154.jl")
 
 end