[lldb] Accept negative indexes in __getitem__

To the Python bindings, add support for Python-like negative indexes.

While was using `script`, I tried to access a thread's bottom frame with
`thread.frame[-1]`, but that failed. This change updates the `__getitem__`
implementations to support negative indexes as one would expect in Python.

Differential Revision: https://reviews.llvm.org/D143282

Author: kastiglione

lldb/bindings/interface/SBBreakpoint.i

@@ -273,8 +273,11 @@ public:
                 return 0
 
             def __getitem__(self, key):
-                if type(key) is int and key < len(self):
-                    return self.sbbreakpoint.GetLocationAtIndex(key)
+                if isinstance(key, int):
+                    count = len(self)
+                    if -count <= key < count:
+                        key %= count
+                        return self.sbbreakpoint.GetLocationAtIndex(key)
                 return None
 
         def get_locations_access_object(self):

lldb/bindings/interface/SBInstructionList.i

@@ -83,7 +83,9 @@ public:
             '''Access instructions by integer index for array access or by lldb.SBAddress to find an instruction that matches a section offset address object.'''
             if type(key) is int:
                 # Find an instruction by index
-                if key < len(self):
+                count = len(self)
+                if -count <= key < count:
+                    key %= count
                     return self.GetInstructionAtIndex(key)
             elif type(key) is SBAddress:
                 # Find an instruction using a lldb.SBAddress object

lldb/bindings/interface/SBModule.i

@@ -415,7 +415,8 @@ public:
             def __getitem__(self, key):
                 count = len(self)
                 if type(key) is int:
-                    if key < count:
+                    if -count <= key < count:
+                        key %= count
                         return self.sbmodule.GetSymbolAtIndex(key)
                 elif type(key) is str:
                     matches = []
@@ -476,7 +477,8 @@ public:
             def __getitem__(self, key):
                 count = len(self)
                 if type(key) is int:
-                    if key < count:
+                    if -count <= key < count:
+                        key %= count
                         return self.sbmodule.GetSectionAtIndex(key)
                 elif type(key) is str:
                     for idx in range(count):
@@ -511,7 +513,8 @@ public:
             def __getitem__(self, key):
                 count = len(self)
                 if type(key) is int:
-                    if key < count:
+                    if -count <= key < count:
+                        key %= count
                         return self.sbmodule.GetCompileUnitAtIndex(key)
                 elif type(key) is str:
                     is_full_path = key[0] == '/'

lldb/bindings/interface/SBProcess.i

@@ -487,8 +487,11 @@ public:
                 return 0
 
             def __getitem__(self, key):
-                if type(key) is int and key < len(self):
-                    return self.sbprocess.GetThreadAtIndex(key)
+                if isinstance(key, int):
+                    count = len(self)
+                    if -count <= key < count:
+                        key %= count
+                        return self.sbprocess.GetThreadAtIndex(key)
                 return None
 
         def get_threads_access_object(self):

lldb/bindings/interface/SBSymbolContextList.i

@@ -74,8 +74,9 @@ public:
 
         def __getitem__(self, key):
             count = len(self)
-            if type(key) is int:
-                if key < count:
+            if isinstance(key, int):
+                if -count <= key < count:
+                    key %= count
                     return self.GetContextAtIndex(key)
                 else:
                     raise IndexError

lldb/bindings/interface/SBTarget.i

@@ -1001,7 +1001,8 @@ public:
             def __getitem__(self, key):
                 num_modules = self.sbtarget.GetNumModules()
                 if type(key) is int:
-                    if key < num_modules:
+                    if -num_modules <= key < num_modules:
+                        key %= num_modules
                         return self.sbtarget.GetModuleAtIndex(key)
                 elif type(key) is str:
                     if key.find('/') == -1:

lldb/bindings/interface/SBThread.i

@@ -434,8 +434,11 @@ public:
                 return 0
 
             def __getitem__(self, key):
-                if type(key) is int and key < self.sbthread.GetNumFrames():
-                    return self.sbthread.GetFrameAtIndex(key)
+                if isinstance(key, int):
+                    count = len(self)
+                    if -count <= key < count:
+                        key %= count
+                        return self.sbthread.GetFrameAtIndex(key)
                 return None
 
         def get_frames_access_object(self):

lldb/bindings/interface/SBTypeCategory.i

@@ -147,7 +147,8 @@ namespace lldb {
                 def __getitem__(self, key):
                     num_items = len(self)
                     if type(key) is int:
-                        if key < num_items:
+                        if -num_items <= key < num_items:
+                            key %= num_items
                             return self.get_at_index_function(self.sbcategory,key)
                     elif type(key) is str:
                         return self.get_by_name_function(self.sbcategory,SBTypeNameSpecifier(key))

lldb/bindings/interface/SBTypeEnumMember.i

@@ -121,7 +121,8 @@ public:
         def __getitem__(self, key):
           num_elements = self.GetSize()
           if type(key) is int:
-              if key < num_elements:
+              if -num_elements <= key < num_elements:
+                  key %= num_elements
                   return self.GetTypeEnumMemberAtIndex(key)
           elif type(key) is str:
               for idx in range(num_elements):

lldb/bindings/interface/SBValue.i

@@ -459,8 +459,11 @@ public:
                 return 0
 
             def __getitem__(self, key):
-                if type(key) is int and key < len(self):
-                    return self.sbvalue.GetChildAtIndex(key)
+                if isinstance(key, int):
+                    count = len(self)
+                    if -count <= key < count:
+                        key %= count
+                        return self.sbvalue.GetChildAtIndex(key)
                 return None
 
         def get_child_access_object(self):