Add semantic::Statement::Block() for getting the owning BlockStatement

Required special casing the ElseStatement, as this isn't actually owned by a BlockStatement.

Change-Id: Ic33c207598b838a12b865a7694e596b2629c9208
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/46443
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>

src/semantic/sem_statement.cc

@@ -12,6 +12,10 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+#include <algorithm>
+
+#include "src/ast/block_statement.h"
+#include "src/debug.h"
 #include "src/semantic/statement.h"
 
 TINT_INSTANTIATE_TYPEINFO(tint::semantic::Statement);
@@ -19,7 +23,17 @@ TINT_INSTANTIATE_TYPEINFO(tint::semantic::Statement);
 namespace tint {
 namespace semantic {
 
-Statement::Statement(ast::Statement* declaration) : declaration_(declaration) {}
+Statement::Statement(const ast::Statement* declaration,
+                     const ast::BlockStatement* block)
+    : declaration_(declaration), block_(block) {
+#ifndef NDEBUG
+  if (block) {
+    auto& stmts = block->statements();
+    TINT_ASSERT(std::find(stmts.begin(), stmts.end(), declaration) !=
+                stmts.end());
+  }
+#endif  //  NDEBUG
+}
 
 }  // namespace semantic
 }  // namespace tint

src/semantic/statement.h

@@ -21,6 +21,7 @@ namespace tint {
 
 // Forward declarations
 namespace ast {
+class BlockStatement;
 class Statement;
 }  // namespace ast
 
@@ -31,13 +32,19 @@ class Statement : public Castable<Statement, Node> {
  public:
   /// Constructor
   /// @param declaration the AST node for this statement
-  explicit Statement(ast::Statement* declaration);
+  /// @param block the owning AST block statement
+  Statement(const ast::Statement* declaration,
+            const ast::BlockStatement* block);
 
   /// @return the AST node for this statement
-  ast::Statement* Declaration() const { return declaration_; }
+  const ast::Statement* Declaration() const { return declaration_; }
+
+  /// @return the owning AST block statement for this statement
+  const ast::BlockStatement* Block() const { return block_; }
 
  private:
-  ast::Statement* const declaration_;
+  ast::Statement const* const declaration_;
+  ast::BlockStatement const* const block_;
 };
 
 }  // namespace semantic

src/semantic/type_mappings.h

@@ -25,6 +25,7 @@ class CallExpression;
 class Expression;
 class Function;
 class MemberAccessorExpression;
+class Statement;
 class StructMember;
 class Variable;
 }  // namespace ast
@@ -41,6 +42,7 @@ class Call;
 class Expression;
 class Function;
 class MemberAccessorExpression;
+class Statement;
 class Struct;
 class StructMember;
 class Variable;
@@ -56,6 +58,7 @@ struct TypeMappings {
   Expression* operator()(ast::Expression*);
   Function* operator()(ast::Function*);
   MemberAccessorExpression* operator()(ast::MemberAccessorExpression*);
+  Statement* operator()(ast::Statement*);
   Struct* operator()(type::Struct*);
   StructMember* operator()(ast::StructMember*);
   Variable* operator()(ast::Variable*);