[astgen] Add ASTNodeKind; support decls in code-blocks.

Author: zoecarver

include/swift/AST/CASTBridging.h

@@ -130,9 +130,15 @@ void *SwiftVarDecl_create(void *ctx, BridgedIdentifier _Nullable name,
 void *IfStmt_create(void *ctx, void *ifLoc, void *cond, void *_Nullable then,
                     void *_Nullable elseLoc, void *_Nullable elseStmt);
 
+typedef enum ENUM_EXTENSIBILITY_ATTR(open) ASTNodeKind : long {
+  ASTNodeKindExpr,
+  ASTNodeKindStmt,
+  ASTNodeKindDecl
+} ASTNodeKind;
+
 struct ASTNodeBridged {
   void *ptr;
-  _Bool isExpr; // Must be expr or stmt.
+  ASTNodeKind kind;
 };
 
 void *BraceStmt_create(void *ctx, void *lbloc, BridgedArrayRef elements,

lib/AST/CASTBridging.cpp

@@ -164,12 +164,16 @@ void *BraceStmt_create(void *ctx, void *lbloc, BridgedArrayRef elements,
                        void *rbloc) {
   llvm::SmallVector<ASTNode, 6> nodes;
   for (auto node : getArrayRef<ASTNodeBridged>(elements)) {
-    if (node.isExpr) {
+    if (node.kind == ASTNodeKindExpr) {
       auto expr = (Expr *)node.ptr;
       nodes.push_back(expr);
-    } else {
+    } else if (node.kind == ASTNodeKindStmt) {
       auto stmt = (Stmt *)node.ptr;
       nodes.push_back(stmt);
+    } else {
+      assert(node.kind == ASTNodeKindDecl);
+      auto decl = (Decl *)node.ptr;
+      nodes.push_back(decl);
     }
   }
 

lib/ASTGen/Sources/ASTGen/ASTGen.swift

@@ -38,9 +38,11 @@ enum ASTNode {
   func bridged() -> ASTNodeBridged {
     switch self {
     case .expr(let e):
-      return ASTNodeBridged(ptr: e, isExpr: true)
+      return ASTNodeBridged(ptr: e, kind: .expr)
     case .stmt(let s):
-      return ASTNodeBridged(ptr: s, isExpr: false)
+      return ASTNodeBridged(ptr: s, kind: .stmt)
+    case .decl(let d):
+      return ASTNodeBridged(ptr: d, kind: .decl)
     default:
       fatalError("Must be expr or stmt.")
     }