Fixes based on @Araq's feedback.

compiler/ast.nim

@@ -1598,7 +1598,7 @@ proc toObject*(typ: PType): PType =
   ## Otherwise ``typ`` is simply returned as-is.
   result = typ
   if result.kind == tyRef:
-    result = result.sons[0]
+    result = result.lastSon
 
 when false:
   proc containsNil*(n: PNode): bool =

compiler/semstmts.nim

@@ -286,7 +286,8 @@ 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:
+        if typeNode.kind == nkInfix and
+            considerQuotedIdent(typeNode[0]).s == "as":
           typeNode = a.sons[j].sons[1]
           symbolNode = a.sons[j].sons[2]
 

compiler/transf.nim

@@ -21,7 +21,7 @@
 import
   intsets, strutils, lists, options, ast, astalgo, trees, treetab, msgs, os,
   idents, renderer, types, passes, semfold, magicsys, cgmeth, rodread,
-  lambdalifting, sempass2, lowerings
+  lambdalifting, sempass2, lowerings, lookups
 
 # implementation
 
@@ -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:
+  if n[0].kind == nkInfix and considerQuotedIdent(n[0][0]).s == "as":
     let excTypeNode = n[0][1]
     let actions = newTransNode(nkStmtList, n[1].info, 2)
     # Generating `let exc = (excType)(getCurrentException())`