fix #19580; add warning for bare except: clause (#21099)

* fix #19580; add warning for bare except: clause

* fixes some easy ones

* Update doc/manual.md

* fixes docs

* Update changelog.md

* addition

* Apply suggestions from code review

Co-authored-by: Jacek Sieka <arnetheduck@gmail.com>

* Update doc/tut2.md

Co-authored-by: Jacek Sieka <arnetheduck@gmail.com>

doc/manual.md

@@ -4773,8 +4773,8 @@ Example:
       echo "overflow!"
     except ValueError, IOError:
       echo "catch multiple exceptions!"
-    except:
-      echo "Unknown exception!"
+    except CatchableError:
+      echo "Catchable exception!"
     finally:
       close(f)
   ```
@@ -4786,9 +4786,6 @@ listed in an `except` clause, the corresponding statements are executed.
 The statements following the `except` clauses are called
 `exception handlers`:idx:.
 
-The empty `except`:idx: clause is executed if there is an exception that is
-not listed otherwise. It is similar to an `else` clause in `if` statements.
-
 If there is a `finally`:idx: clause, it is always executed after the
 exception handlers.
 
@@ -4806,11 +4803,11 @@ 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`:
 
-  ```nim
+  ```nim test
   from std/strutils import parseInt
 
   let x = try: parseInt("133a")
-          except: -1
+          except ValueError: -1
           finally: echo "hi"
   ```
 
@@ -4818,8 +4815,9 @@ branch always has to be `void`:
 To prevent confusing code there is a parsing limitation; if the `try`
 follows a `(` it has to be written as a one liner:
 
-  ```nim
-  let x = (try: parseInt("133a") except: -1)
+  ```nim test
+  from std/strutils import parseInt
+  let x = (try: parseInt("133a") except ValueError: -1)
   ```
 
 
@@ -4867,7 +4865,7 @@ error message from `e`, and for such situations, it is enough to use
   ```nim
   try:
     # ...
-  except:
+  except CatchableError:
     echo getCurrentExceptionMsg()
   ```
 
@@ -5055,7 +5053,7 @@ An empty `raises` list (`raises: []`) means that no exception may be raised:
     try:
       unsafeCall()
       result = true
-    except:
+    except CatchableError:
       result = false
   ```
 

doc/tut2.md

@@ -393,7 +393,7 @@ The `try` statement handles exceptions:
       echo "could not convert string to integer"
     except IOError:
       echo "IO error!"
-    except:
+    except CatchableError:
       echo "Unknown exception!"
       # reraise the unknown exception:
       raise
@@ -425,7 +425,7 @@ module. Example:
   ```nim
   try:
     doSomethingHere()
-  except:
+  except CatchableError:
     let
       e = getCurrentException()
       msg = getCurrentExceptionMsg()