WIP: as with generics.

compiler/lookups.nim

@@ -434,3 +434,6 @@ proc pickSym*(c: PContext, n: PNode; kind: TSymKind;
     if a.kind == kind and flags <= a.flags:
       return a
     a = nextOverloadIter(o, c, n)
+
+proc isExceptAs*(n: PNode): bool =
+  return n.kind == nkInfix and considerQuotedIdent(n[0]).s == "as"

compiler/semgnrc.nim

@@ -339,8 +339,17 @@ proc semGenericStmt(c: PContext, n: PNode,
       checkMinSonsLen(a, 1)
       var L = sonsLen(a)
       for j in countup(0, L-2):
+        debug(a.sons[j])
+        if a.sons[j].isExceptAs():
+          openScope(c)
+          addTempDecl(c, getIdentNode(a.sons[j][2]), skLet)
+          a.sons[j] = semGenericStmt(c, a.sons[j][1], flags+{withinTypeDesc}, ctx)
+          closeScope(c)
+        else:
           a.sons[j] = semGenericStmt(c, a.sons[j], flags+{withinTypeDesc}, ctx)
+      debug(a)
       a.sons[L-1] = semGenericStmtScope(c, a.sons[L-1], flags, ctx)
+
   of nkVarSection, nkLetSection:
     for i in countup(0, sonsLen(n) - 1):
       var a = n.sons[i]

compiler/semstmts.nim

@@ -286,8 +286,7 @@ proc semTry(c: PContext, n: PNode): PNode =
         var typeNode = a.sons[j] # e.g. `Exception`
         var symbolNode: PNode = nil # e.g. `foobar`
         # Handle the case where the `Exception as foobar` syntax is used.
-        if typeNode.kind == nkInfix and
+        if typeNode.isExceptAs():
-            considerQuotedIdent(typeNode[0]).s == "as":
           typeNode = a.sons[j].sons[1]
           symbolNode = a.sons[j].sons[2]
 

compiler/transf.nim

@@ -703,7 +703,7 @@ proc transformCall(c: PTransf, n: PNode): PTransNode =
 
 proc transformExceptBranch(c: PTransf, n: PNode): PTransNode =
   result = transformSons(c, n)
-  if n[0].kind == nkInfix and considerQuotedIdent(n[0][0]).s == "as":
+  if n[0].isExceptAs():
     let excTypeNode = n[0][1]
     let actions = newTransNode(nkStmtList, n[1].info, 2)
     # Generating `let exc = (excType)(getCurrentException())`

tests/exception/texcas.nim

@@ -1,10 +1,10 @@
 discard """
   output: '''Hello'''
 """
-
+proc test[T]() =
   try:
-  raise newException(Exception, "Hello")
+    raise newException(T, "Hello")
-except Exception as foobar:
+  except T as foobar:
     echo(foobar.msg)
 
-
+test[Exception]()