Introduce SwitchExprSyntax

This replaces SwitchStmtSyntax, and will be
wrapped in an ExpressionStmtSyntax when used as a
statement.

Author: hamishknight

gyb_syntax_support/ExprNodes.py

@@ -307,6 +307,73 @@
                    is_optional=True),
          ]),
 
+    # switch-expr -> identifier? ':'? 'switch' expr '{'
+    #   switch-case-list '}' ';'?
+    #
+    # This node represents both a 'switch' expression, as well as a 'switch'
+    # statement when wrapped in a ExpressionStmt node.
+    Node('SwitchExpr', name_for_diagnostics="'switch' statement", kind='Expr',
+         traits=['Braced'],
+         children=[
+             Child('SwitchKeyword', kind='SwitchToken'),
+             Child('Expression', kind='Expr'),
+             Child('LeftBrace', kind='LeftBraceToken'),
+             Child('Cases', kind='SwitchCaseList',
+                   collection_element_name='Case'),
+             Child('RightBrace', kind='RightBraceToken',
+                   requires_leading_newline=True),
+         ]),
+
+    # switch-case-list -> switch-case switch-case-list?
+    Node('SwitchCaseList', name_for_diagnostics=None, kind='SyntaxCollection',
+         element='Syntax', element_name='SwitchCase',
+         element_choices=['SwitchCase', 'IfConfigDecl'],
+         elements_separated_by_newline=True),
+
+    # switch-case -> unknown-attr? switch-case-label stmt-list
+    #              | unknown-attr? switch-default-label stmt-list
+    Node('SwitchCase', name_for_diagnostics='switch case', kind='Syntax',
+         traits=['WithStatements'],
+         parser_function='parseSwitchCase',
+         children=[
+             Child('UnknownAttr', kind='Attribute', is_optional=True),
+             Child('Label', kind='Syntax', name_for_diagnostics='label',
+                   node_choices=[
+                       Child('Default', kind='SwitchDefaultLabel'),
+                       Child('Case', kind='SwitchCaseLabel'),
+                   ]),
+             Child('Statements', kind='CodeBlockItemList',
+                   collection_element_name='Statement',
+                   is_indented=True),
+         ]),
+
+    # switch-case-label -> 'case' case-item-list ':'
+    Node('SwitchCaseLabel', name_for_diagnostics=None, kind='Syntax',
+         children=[
+             Child('CaseKeyword', kind='CaseToken'),
+             Child('CaseItems', kind='CaseItemList',
+                   collection_element_name='CaseItem'),
+             Child('Colon', kind='ColonToken'),
+         ]),
+
+    # switch-default-label -> 'default' ':'
+    Node('SwitchDefaultLabel', name_for_diagnostics=None, kind='Syntax',
+         children=[
+             Child('DefaultKeyword', kind='DefaultToken'),
+             Child('Colon', kind='ColonToken'),
+         ]),
+
+    # case-item -> pattern where-clause? ','?
+    Node('CaseItem', name_for_diagnostics=None, kind='Syntax',
+         traits=['WithTrailingComma'],
+         children=[
+             Child('Pattern', kind='Pattern'),
+             Child('WhereClause', kind='WhereClause',
+                   is_optional=True),
+             Child('TrailingComma', kind='CommaToken',
+                   is_optional=True),
+         ]),
+
     # ? expr :
     # Ternary expression without the condition and the second choice.
     # NOTE: This appears only in SequenceExpr.

gyb_syntax_support/StmtNodes.py

@@ -42,12 +42,6 @@
              Child('Expression', kind='Expr'),
          ]),
 
-    # switch-case-list -> switch-case switch-case-list?
-    Node('SwitchCaseList', name_for_diagnostics=None, kind='SyntaxCollection',
-         element='Syntax', element_name='SwitchCase',
-         element_choices=['SwitchCase', 'IfConfigDecl'],
-         elements_separated_by_newline=True),
-
     # repeat-while-stmt -> label? ':'? 'repeat' code-block 'while' expr ';'?
     Node('RepeatWhileStmt', name_for_diagnostics="'repeat' statement", kind='Stmt',
          traits=['WithCodeBlock'],
@@ -99,20 +93,6 @@
              Child('Body', kind='CodeBlock', name_for_diagnostics='body'),
          ]),
 
-    # switch-stmt -> identifier? ':'? 'switch' expr '{'
-    #   switch-case-list '}' ';'?
-    Node('SwitchStmt', name_for_diagnostics="'switch' statement", kind='Stmt',
-         traits=['Braced'],
-         children=[
-             Child('SwitchKeyword', kind='SwitchToken'),
-             Child('Expression', kind='Expr'),
-             Child('LeftBrace', kind='LeftBraceToken'),
-             Child('Cases', kind='SwitchCaseList',
-                   collection_element_name='Case'),
-             Child('RightBrace', kind='RightBraceToken',
-                   requires_leading_newline=True),
-         ]),
-
     # catch-clause-list -> catch-clause catch-clause-list?
     Node('CatchClauseList', name_for_diagnostics="'catch' clause",
          kind='SyntaxCollection', element='CatchClause'),
@@ -271,41 +251,6 @@
              Child('Expression', kind='Expr'),
          ]),
 
-    # switch-case -> unknown-attr? switch-case-label stmt-list
-    #              | unknown-attr? switch-default-label stmt-list
-    Node('SwitchCase', name_for_diagnostics='switch case', kind='Syntax',
-         traits=['WithStatements'],
-         parser_function='parseSwitchCase',
-         children=[
-             Child('UnknownAttr', kind='Attribute', is_optional=True),
-             Child('Label', kind='Syntax', name_for_diagnostics='label',
-                   node_choices=[
-                       Child('Default', kind='SwitchDefaultLabel'),
-                       Child('Case', kind='SwitchCaseLabel'),
-                   ]),
-             Child('Statements', kind='CodeBlockItemList',
-                   collection_element_name='Statement',
-                   is_indented=True),
-         ]),
-
-    # switch-default-label -> 'default' ':'
-    Node('SwitchDefaultLabel', name_for_diagnostics=None, kind='Syntax',
-         children=[
-             Child('DefaultKeyword', kind='DefaultToken'),
-             Child('Colon', kind='ColonToken'),
-         ]),
-
-    # case-item -> pattern where-clause? ','?
-    Node('CaseItem', name_for_diagnostics=None, kind='Syntax',
-         traits=['WithTrailingComma'],
-         children=[
-             Child('Pattern', kind='Pattern'),
-             Child('WhereClause', kind='WhereClause',
-                   is_optional=True),
-             Child('TrailingComma', kind='CommaToken',
-                   is_optional=True),
-         ]),
-
     # catch-item -> pattern? where-clause? ','?
     Node('CatchItem', name_for_diagnostics=None, kind='Syntax',
          traits=['WithTrailingComma'],
@@ -317,15 +262,6 @@
                    is_optional=True),
          ]),
 
-    # switch-case-label -> 'case' case-item-list ':'
-    Node('SwitchCaseLabel', name_for_diagnostics=None, kind='Syntax',
-         children=[
-             Child('CaseKeyword', kind='CaseToken'),
-             Child('CaseItems', kind='CaseItemList',
-                   collection_element_name='CaseItem'),
-             Child('Colon', kind='ColonToken'),
-         ]),
-
     # catch-clause 'catch' case-item-list? code-block
     Node('CatchClause', name_for_diagnostics="'catch' clause", kind='Syntax',
          traits=['WithCodeBlock'],