start initial match impl

src/match/emit/mod.jl

@@ -1,2 +1,11 @@
-function emit(value, expr::Pattern.Type, body)
+function emit(info::EmitInfo)
+    quote
+        let $(info.value_holder) = $(info.value)
+            if cond
+                body
+                @goto $(info.final_label)
+            end
+        end
+        @label $(info.final_label)
+    end
 end

src/match/scan.jl

@@ -3,6 +3,7 @@ struct EmitInfo
     value::Any
     patterns::Vector{Pattern.Type}
     exprs::Vector{Any}
+    value_holder::Symbol
     final_label::Symbol
     return_var::Symbol
     source
@@ -31,7 +32,14 @@ function EmitInfo(mod::Module, value, body, source = nothing)
         throw(SyntaxError("invalid pattern table: $body"; source))
     end
 
-    return EmitInfo(mod, value, patterns, exprs, gensym("final"), gensym("return"), source)
+    return EmitInfo(
+        mod, value, patterns,
+        exprs,
+        gensym("value"),
+        gensym("final"),
+        gensym("return"),
+        source
+    )
 end
 
 function expr2pattern(expr)

test/match/data.jl

@@ -1,4 +1,4 @@
-using Liang.Match: EmitInfo, Pattern, expr2pattern
+using Liang.Match: Match, EmitInfo, Pattern, expr2pattern
 using Liang.Expression: Scalar
 
 expr2pattern(:(1:10))
@@ -53,3 +53,5 @@ info = EmitInfo(Main, :x, quote
     (a, b) && c => a + b
     [x, y, 2, 3] => x
 end)
+
+Match.emit(info)