Enhance handling syntax errors with TRY/EXCEPT.

Show unexecuted TRY/EXCEPT branches if there are syntax errors.

Make invalid TRY/EXCEPT itself a syntax error. Fixes #4484.

atest/robot/running/try_except/invalid_try_except.robot

@@ -81,3 +81,6 @@ CONTINUE in FINALLY
 
 RETURN in FINALLY
     TRY:PASS    FINALLY:FAIL    path=body[0].body[0]
+
+Invalid TRY/EXCEPT causes syntax error that cannot be caught
+    TRY:FAIL    EXCEPT:NOT RUN    ELSE:NOT RUN

atest/robot/running/try_except/try_except.robot

@@ -35,7 +35,7 @@ Default except pattern
     FAIL    PASS
 
 Syntax errors cannot be caught
-    FAIL
+    FAIL    NOT RUN    NOT RUN
 
 Finally block executed when no failures
     [Template]    None

atest/testdata/running/try_except/invalid_try_except.robot

@@ -261,6 +261,19 @@ RETURN in FINALLY
     [Documentation]    FAIL    RETURN cannot be used in FINALLY branch.
     RETURN in FINALLY
 
+Invalid TRY/EXCEPT causes syntax error that cannot be caught
+    [Documentation]    FAIL    TRY branch cannot be empty.
+    TRY
+        TRY
+        EXCEPT
+            Fail    Not run
+        END
+    EXCEPT
+        Fail    Not run because error cannot be caught
+    ELSE
+        Fail    Not run either
+    END
+
 *** Keywords ***
 RETURN in FINALLY
     TRY

atest/testdata/running/try_except/try_except.robot

@@ -91,6 +91,8 @@ Syntax errors cannot be caught
         ${y} =    ${x}     Set Variable
     EXCEPT
         Fail    Should not be run
+    ELSE
+        Fail    Should not be run
     END
 
 Finally block executed when no failures

src/robot/running/bodyrunner.py

@@ -482,7 +482,7 @@ def run(self, data):
         with StatusReporter(data, TryResult(), self._context, run):
             if data.error:
                 self._run_invalid(data)
-                return False
+                return
             error = self._run_try(data, run)
             run_excepts_or_else = self._should_run_excepts_or_else(error, run)
             if error:
@@ -504,8 +504,8 @@ def _run_invalid(self, data):
                 runner.run(branch.body)
                 if not error_reported:
                     error_reported = True
-                    raise ExecutionFailed(data.error)
-        raise ExecutionFailed(data.error)
+                    raise DataError(data.error, syntax=True)
+        raise ExecutionFailed(data.error, syntax=True)
 
     def _run_try(self, data, run):
         result = TryBranchResult(data.TRY)
@@ -516,7 +516,7 @@ def _should_run_excepts_or_else(self, error, run):
             return False
         if not error:
             return True
-        return not (error.skip or isinstance(error, ExecutionPassed))
+        return not (error.skip or error.syntax or isinstance(error, ExecutionPassed))
 
     def _run_branch(self, branch, result, run=True, error=None):
         try:
@@ -526,8 +526,6 @@ def _run_branch(self, branch, result, run=True, error=None):
                 runner = BodyRunner(self._context, run, self._templated)
                 runner.run(branch.body)
         except ExecutionStatus as err:
-            if isinstance(err, ExecutionFailed) and err.syntax:
-                raise err
             return err
         else:
             return None

src/robot/running/statusreporter.py

@@ -62,7 +62,7 @@ def __exit__(self, exc_type, exc_val, exc_tb):
             context.test.status = result.status
         result.endtime = get_timestamp()
         context.end_keyword(ModelCombiner(self.data, result))
-        if failure is not exc_val:
+        if failure is not exc_val and not self.suppress:
             raise failure
         return self.suppress