fixes #1742

compiler/ccgstmts.nim

@@ -798,7 +798,9 @@ proc genTryCpp(p: BProc, t: PNode, d: var TLoc) =
     startBlock(p)
     var finallyBlock = t.lastSon
     if finallyBlock.kind == nkFinally:
-      expr(p, finallyBlock.sons[0], d)
+      #expr(p, finallyBlock.sons[0], d)
+      genStmts(p, finallyBlock.sons[0])
+
     line(p, cpsStmts, ~"throw;$n")
     endBlock(p)
   
@@ -807,7 +809,7 @@ proc genTryCpp(p: BProc, t: PNode, d: var TLoc) =
   
   discard pop(p.nestedTryStmts)
   if (i < length) and (t.sons[i].kind == nkFinally):
-    exprBlock(p, t.sons[i].sons[0], d)
+    genSimpleBlock(p, t.sons[i].sons[0])
   
 proc genTry(p: BProc, t: PNode, d: var TLoc) = 
   # code to generate:
@@ -899,7 +901,7 @@ proc genTry(p: BProc, t: PNode, d: var TLoc) =
   endBlock(p) # end of else block
   if i < length and t.sons[i].kind == nkFinally:
     p.finallySafePoints.add(safePoint)
-    exprBlock(p, t.sons[i].sons[0], d)
+    genSimpleBlock(p, t.sons[i].sons[0])
     discard pop(p.finallySafePoints)
   linefmt(p, cpsStmts, "if ($1.status != 0) #reraiseException();$n", safePoint)
 

compiler/jsgen.nim

@@ -601,15 +601,13 @@ proc genTry(p: PProc, n: PNode, r: var TCompRes) =
   if p.target == targetJS:
     app(p.body, "} finally {" & tnl & "excHandler = excHandler.prev;" & tnl)
   if i < length and n.sons[i].kind == nkFinally:
-    gen(p, n.sons[i].sons[0], a)
+    genStmt(p, n.sons[i].sons[0])
-    moveInto(p, a, r)
   if p.target == targetJS:
     app(p.body, "}" & tnl)
   if p.target == targetLua:
     # we need to repeat the finally block for Lua ...
     if i < length and n.sons[i].kind == nkFinally:
-      gen(p, n.sons[i].sons[0], a)
+      genStmt(p, n.sons[i].sons[0])
-      moveInto(p, a, r)
 
 proc genRaiseStmt(p: PProc, n: PNode) =
   genLineDir(p, n)

compiler/parser.nim

@@ -505,7 +505,7 @@ proc parsePar(p: var TParser): PNode =
   getTok(p)
   optInd(p, result)
   if p.tok.tokType in {tkDiscard, tkInclude, tkIf, tkWhile, tkCase, 
-                       tkTry, tkFinally, tkExcept, tkFor, tkBlock, 
+                       tkTry, tkDefer, tkFinally, tkExcept, tkFor, tkBlock, 
                        tkConst, tkLet, tkWhen, tkVar,
                        tkMixin}:
     # XXX 'bind' used to be an expression, so we exclude it here;

compiler/semstmts.nim

@@ -263,7 +263,8 @@ proc semTry(c: PContext, n: PNode): PNode =
   n.sons[0] = semExprBranchScope(c, n.sons[0])
   typ = commonType(typ, n.sons[0].typ)
   var check = initIntSet()
-  for i in countup(1, sonsLen(n) - 1): 
+  var last = sonsLen(n) - 1
+  for i in countup(1, last):
     var a = n.sons[i]
     checkMinSonsLen(a, 1)
     var length = sonsLen(a)
@@ -286,7 +287,8 @@ proc semTry(c: PContext, n: PNode): PNode =
       illFormedAst(n)
     # last child of an nkExcept/nkFinally branch is a statement:
     a.sons[length-1] = semExprBranchScope(c, a.sons[length-1])
-    typ = commonType(typ, a.sons[length-1].typ)
+    if a.kind != nkFinally: typ = commonType(typ, a.sons[length-1].typ)
+    else: dec last
   dec c.p.inTryStmt
   if isEmptyType(typ) or typ.kind == tyNil:
     discardCheck(c, n.sons[0])
@@ -294,8 +296,9 @@ proc semTry(c: PContext, n: PNode): PNode =
     if typ == enforceVoidContext:
       result.typ = enforceVoidContext
   else:
+    if n.lastSon.kind == nkFinally: discardCheck(c, n.lastSon.lastSon)
     n.sons[0] = fitNode(c, typ, n.sons[0])
-    for i in 1..n.len-1:
+    for i in 1..last:
       var it = n.sons[i]
       let j = it.len-1
       it.sons[j] = fitNode(c, typ, it.sons[j])
@@ -1251,6 +1254,7 @@ proc semStmtList(c: PContext, n: PNode, flags: TExprFlags): PNode =
       tryStmt.addSon(deferPart)
       n.sons[i] = semTry(c, tryStmt)
       n.sons.setLen(i+1)
+      n.typ = n.sons[i].typ
       return
     else:
       n.sons[i] = semExpr(c, n.sons[i])

compiler/vmgen.nim

@@ -463,7 +463,7 @@ proc genTry(c: PCtx; n: PNode; dest: var TDest) =
   # from the stack
   c.gABx(fin, opcFinally, 0, 0)
   if fin.kind == nkFinally:
-    c.gen(fin.sons[0], dest)
+    c.gen(fin.sons[0])
     c.clearDest(n, dest)
   c.gABx(fin, opcFinallyEnd, 0, 0)
 

doc/manual/exceptions.txt

@@ -47,6 +47,27 @@ the rest of the procedure - that is not within a ``finally`` clause -
 is not executed (if an exception occurs).
 
 
+Try expression
+--------------
+
+Try can also be used as an expression; the type of the ``try`` branch then
+needs to fit the types of ``except`` branches, but the type of the ``finally``
+branch always has to be ``void``:
+
+.. code-block:: nim
+  let x = try: parseInt("133a")
+          except: -1
+          finally: echo "hi"
+
+
+To prevent confusing code there is a parsing limitation; if the ``try``
+follows a ``(`` it has to be written as a one liner:
+
+.. code-block:: nim
+  let x = (try: parseInt("133a") except: -1)
+
+
+
 Defer statement
 ---------------