unified: Factor catch/case guards into conditional_pattern

The where-clause needs to be attached to the individual pattern, not the catch/case.

unified/extractor/ast_types.yml

@@ -49,6 +49,7 @@ supertypes:
     - tuple_pattern
     - constructor_pattern
     - or_pattern
+    - conditional_pattern
     - ignore_pattern
     - expr_equality_pattern
     - bulk_importing_pattern
@@ -369,7 +370,6 @@ named:
   catch_clause:
     modifier*: modifier
     pattern?: pattern
-    guard?: expr
     body: block
 
   # `switch value { case pattern: body case ...: default: body }`
@@ -381,11 +381,9 @@ named:
   # A single `case ...:` (or `default:`) entry in a switch.
   # An entry with multiple `case p1, p2:` patterns uses an `or_pattern`.
   # A `default:` entry has no pattern.
-  # An optional `guard` corresponds to a `where`-clause on the case.
   switch_case:
     modifier*: modifier
     pattern?: pattern
-    guard?: expr
     body: block
 
   # Evaluate 'expr' and match its result against 'pattern', and return true if it matches.
@@ -446,6 +444,14 @@ named:
     modifier*: modifier
     pattern*: pattern
 
+  # A pattern that matches against a nested pattern, and subsequently checks a condition.
+  # The match is rejected if the condition does not hold.
+  # Variables bound in the nested pattern are in scope within the condition.
+  conditional_pattern:
+    modifier*: modifier
+    condition: expr
+    pattern: pattern
+
   # A pattern with an optional associated name.
   pattern_element:
     modifier*: modifier

unified/ql/lib/codeql/unified/Ast.qll

@@ -427,6 +427,28 @@ module Unified {
     }
   }
 
+  /** A class representing `conditional_pattern` nodes. */
+  final class ConditionalPattern extends @unified_conditional_pattern, AstNodeImpl {
+    /** Gets the name of the primary QL class for this element. */
+    final override string getAPrimaryQlClass() { result = "ConditionalPattern" }
+
+    /** Gets the node corresponding to the field `condition`. */
+    final Expr getCondition() { unified_conditional_pattern_def(this, result, _) }
+
+    /** Gets the node corresponding to the field `modifier`. */
+    final Modifier getModifier(int i) { unified_conditional_pattern_modifier(this, i, result) }
+
+    /** Gets the node corresponding to the field `pattern`. */
+    final Pattern getPattern() { unified_conditional_pattern_def(this, _, result) }
+
+    /** Gets a field or child node of this node. */
+    final override AstNode getAFieldOrChild() {
+      unified_conditional_pattern_def(this, result, _) or
+      unified_conditional_pattern_modifier(this, _, result) or
+      unified_conditional_pattern_def(this, _, result)
+    }
+  }
+
   /** A class representing `constructor_declaration` nodes. */
   final class ConstructorDeclaration extends @unified_constructor_declaration, AstNodeImpl {
     /** Gets the name of the primary QL class for this element. */
@@ -1565,6 +1587,12 @@ module Unified {
       or
       result = node.(CompoundAssignExpr).getValue() and i = -1 and name = "getValue"
       or
+      result = node.(ConditionalPattern).getCondition() and i = -1 and name = "getCondition"
+      or
+      result = node.(ConditionalPattern).getModifier(i) and name = "getModifier"
+      or
+      result = node.(ConditionalPattern).getPattern() and i = -1 and name = "getPattern"
+      or
       result = node.(ConstructorDeclaration).getBody() and i = -1 and name = "getBody"
       or
       result = node.(ConstructorDeclaration).getModifier(i) and name = "getModifier"

unified/ql/lib/unified.dbscheme

@@ -365,6 +365,19 @@ unified_compound_assign_expr_def(
   int value: @unified_expr ref
 );
 
+#keyset[unified_conditional_pattern, index]
+unified_conditional_pattern_modifier(
+  int unified_conditional_pattern: @unified_conditional_pattern ref,
+  int index: int ref,
+  unique int modifier: @unified_token_modifier ref
+);
+
+unified_conditional_pattern_def(
+  unique int id: @unified_conditional_pattern,
+  int condition: @unified_expr ref,
+  int pattern: @unified_pattern ref
+);
+
 #keyset[unified_constructor_declaration, index]
 unified_constructor_declaration_modifier(
   int unified_constructor_declaration: @unified_constructor_declaration ref,
@@ -1085,7 +1098,7 @@ unified_trivia_tokeninfo(
   string value: string ref
 );
 
-@unified_ast_node = @unified_accessor_declaration | @unified_argument | @unified_array_literal | @unified_assign_expr | @unified_associated_type_declaration | @unified_base_type | @unified_binary_expr | @unified_block | @unified_bound_type_constraint | @unified_break_expr | @unified_bulk_importing_pattern | @unified_call_expr | @unified_catch_clause | @unified_class_like_declaration | @unified_compound_assign_expr | @unified_constructor_declaration | @unified_constructor_pattern | @unified_continue_expr | @unified_destructor_declaration | @unified_do_while_stmt | @unified_equality_type_constraint | @unified_expr_equality_pattern | @unified_for_each_stmt | @unified_function_declaration | @unified_function_expr | @unified_function_type_expr | @unified_generic_type_expr | @unified_guard_if_stmt | @unified_if_expr | @unified_import_declaration | @unified_initializer_declaration | @unified_key_value_pair | @unified_labeled_stmt | @unified_map_literal | @unified_member_access_expr | @unified_name_expr | @unified_name_pattern | @unified_named_type_expr | @unified_operator_syntax_declaration | @unified_or_pattern | @unified_parameter | @unified_pattern_element | @unified_pattern_guard_expr | @unified_return_expr | @unified_switch_case | @unified_switch_expr | @unified_throw_expr | @unified_token | @unified_top_level | @unified_trivia_token | @unified_try_expr | @unified_tuple_expr | @unified_tuple_pattern | @unified_tuple_type_element | @unified_tuple_type_expr | @unified_type_alias_declaration | @unified_type_cast_expr | @unified_type_parameter | @unified_type_test_expr | @unified_type_test_pattern | @unified_unary_expr | @unified_unresolved_operator_sequence | @unified_variable_declaration | @unified_while_stmt
+@unified_ast_node = @unified_accessor_declaration | @unified_argument | @unified_array_literal | @unified_assign_expr | @unified_associated_type_declaration | @unified_base_type | @unified_binary_expr | @unified_block | @unified_bound_type_constraint | @unified_break_expr | @unified_bulk_importing_pattern | @unified_call_expr | @unified_catch_clause | @unified_class_like_declaration | @unified_compound_assign_expr | @unified_conditional_pattern | @unified_constructor_declaration | @unified_constructor_pattern | @unified_continue_expr | @unified_destructor_declaration | @unified_do_while_stmt | @unified_equality_type_constraint | @unified_expr_equality_pattern | @unified_for_each_stmt | @unified_function_declaration | @unified_function_expr | @unified_function_type_expr | @unified_generic_type_expr | @unified_guard_if_stmt | @unified_if_expr | @unified_import_declaration | @unified_initializer_declaration | @unified_key_value_pair | @unified_labeled_stmt | @unified_map_literal | @unified_member_access_expr | @unified_name_expr | @unified_name_pattern | @unified_named_type_expr | @unified_operator_syntax_declaration | @unified_or_pattern | @unified_parameter | @unified_pattern_element | @unified_pattern_guard_expr | @unified_return_expr | @unified_switch_case | @unified_switch_expr | @unified_throw_expr | @unified_token | @unified_top_level | @unified_trivia_token | @unified_try_expr | @unified_tuple_expr | @unified_tuple_pattern | @unified_tuple_type_element | @unified_tuple_type_expr | @unified_type_alias_declaration | @unified_type_cast_expr | @unified_type_parameter | @unified_type_test_expr | @unified_type_test_pattern | @unified_unary_expr | @unified_unresolved_operator_sequence | @unified_variable_declaration | @unified_while_stmt
 
 unified_ast_node_location(
   unique int node: @unified_ast_node ref,