Merge pull request #465 from memoryruins/case-declarations

Wrap Javascript case clauses in brackets to prevent conflicting declarations

src/Compiler/ES/ES.idr

@@ -383,8 +383,8 @@ mutual
     pure $ nSpaces indent ++ "while(true){\n" ++ !(imperative2es (indent+1) x) ++ "\n" ++ nSpaces indent ++ "}"
 
   alt2es : {auto d : Ref Ctxt Defs} -> {auto c : Ref ESs ESSt} -> Nat -> (ImperativeExp, ImperativeStatement) -> Core String
-  alt2es indent (e, b) = pure $ nSpaces indent ++ "case " ++ !(impExp2es e) ++ ":\n" ++
-                                !(imperative2es (indent+1) b) ++ "\n" ++ nSpaces (indent+1) ++ "break;\n"
+  alt2es indent (e, b) = pure $ nSpaces indent ++ "case " ++ !(impExp2es e) ++ ": {\n" ++
+                                !(imperative2es (indent+1) b) ++ "\n" ++ nSpaces (indent+1) ++ "break; }\n"
 
 static_preamble : List String
 static_preamble =

tests/Main.idr

@@ -131,6 +131,7 @@ nodeTests
     , "node011", "node012", "node015", "node017", "node018", "node019" -- node014
     , "node021" --, "node020"
     , "reg001"
+    , "syntax001"
     , "tailrec001"
     ]
 

tests/node/syntax001/caseBlock.idr

@@ -0,0 +1,27 @@
+module Main
+
+-- When generating javasript from idris, it is possible that the same name may appear in
+-- different clauses when translating cases from Idris. To avoid a javascript syntax error
+-- from occuring due to duplicate declations, each case clause is wrapped in brackets
+-- to create unique block scopes.
+
+-- https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/switch
+
+-- Without wrapping in a block, the test error may look like the following:
+-- syntax001/build/exec/_tmp_node.js:39
+-- const x = ({h:1});
+--         ^
+-- SyntaxError: Identifier 'x' has already been declared
+
+test : Bool -> Int
+test x @ True =
+  case x of
+    _ => 0
+test x @ False =
+  case x of
+    _ => 1
+
+main : IO ()
+main = do
+  printLn $ test True
+  printLn $ test False

tests/node/syntax001/expected

@@ -0,0 +1,2 @@
+0
+1

tests/node/syntax001/run

@@ -0,0 +1,3 @@
+$1 --cg node caseBlock.idr -x main
+
+rm -rf build