feat(constants): implement literal constants with lexical scope

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

6 files changed, 26 insertions, 1 deletions

diff --git a/include/cps/AST.h b/include/cps/AST.h
index 87c9341..1afc359 100644
--- a/include/cps/AST.h
+++ b/include/cps/AST.h
@@ -105,6 +105,16 @@ public:
 
 class ThrowStmtAST : public StmtAST {};
 
+class ConstantStmtAST : public StmtAST {
+    std::string Name;
+    std::unique_ptr<ExprAST> Value;
+public:
+    ConstantStmtAST(std::string Name, std::unique_ptr<ExprAST> Value)
+        : Name(std::move(Name)), Value(std::move(Value)) {}
+    const std::string &getName() const { return Name; }
+    ExprAST *getValue() const { return Value.get(); }
+};
+
 class DeclareStmtAST : public StmtAST {
     std::string Name;
     std::string Type;
diff --git a/include/cps/CodeGen.h b/include/cps/CodeGen.h
index 4259d63..2ba5e79 100644
--- a/include/cps/CodeGen.h
+++ b/include/cps/CodeGen.h
@@ -13,6 +13,7 @@
 
 #include <map>
 #include <memory>
+#include <optional>
 #include <string>
 
 namespace cps {
@@ -27,6 +28,16 @@ class CodeGen {
     std::unique_ptr<llvm::Module> TheModule;
     std::unique_ptr<llvm::IRBuilder<>> Builder;
     std::map<std::string, SymbolInfo> Symbols;
+    struct ConstantScope {
+        unsigned ID;
+        std::map<std::string, std::optional<SymbolInfo>> Saved;
+    };
+    std::vector<ConstantScope> ConstantScopes = {{0, {}}};
+    unsigned NextScopeID = 1;
+    void emitScopedBlock(const std::vector<std::unique_ptr<StmtAST>> &Body);
+    bool prepareSymbolDeclaration(const std::string &Name, bool IsConstant = false);
+    bool requireWritable(const SymbolInfo &Info, const std::string &Name);
+    void emitConstantStmt(ConstantStmtAST *Stmt);
     std::unique_ptr<TypeSystem> Types;
 
     std::unique_ptr<ArrayHandler> Arrays;
diff --git a/include/cps/FunctionGen.h b/include/cps/FunctionGen.h
index a7cead5..80c91ea 100644
--- a/include/cps/FunctionGen.h
+++ b/include/cps/FunctionGen.h
@@ -81,7 +81,7 @@ public:
 
     llvm::Function *emitPrototype(PrototypeAST *Proto);
 
-    llvm::Function *emitFunctionDef(FunctionDefAST *FuncAST, const std::function<void(StmtAST*)> &StmtEmitter);
+    llvm::Function *emitFunctionDef(FunctionDefAST *FuncAST, const std::function<void(StmtAST*)> &StmtEmitter, unsigned ScopeID);
 
     llvm::Value *emitCallExpr(CallExprAST *Call, const std::vector<llvm::Value*> &Args);
     
diff --git a/include/cps/Lexer.h b/include/cps/Lexer.h
index 7f3d5b5..efedec8 100644
--- a/include/cps/Lexer.h
+++ b/include/cps/Lexer.h
@@ -14,6 +14,7 @@ enum Token {
     tok_input = -4,
     tok_output = -5,
     
+    tok_constant = -43,
     tok_case = -40,
     tok_endcase = -41,
     tok_otherwise = -42,
diff --git a/include/cps/Parser.h b/include/cps/Parser.h
index 921480d..0079c8b 100644
--- a/include/cps/Parser.h
+++ b/include/cps/Parser.h
@@ -57,6 +57,7 @@ class Parser {
     std::unique_ptr<StmtAST> ParseForStmt();
     
     std::unique_ptr<StmtAST> ParseDeclare();
+    std::unique_ptr<StmtAST> ParseConstant();
     std::unique_ptr<StmtAST> ParseAssignStmt();
     bool ParseDesignatorSuffix(std::vector<DesignatorAccess> &Out);
 
diff --git a/include/cps/TypeSystem.h b/include/cps/TypeSystem.h
index a07c75f..b615ed8 100644
--- a/include/cps/TypeSystem.h
+++ b/include/cps/TypeSystem.h
@@ -106,6 +106,8 @@ struct SymbolInfo {
     llvm::Value *Storage = nullptr;
     std::string TypeName;
     bool IsArray = false;
+    llvm::Constant *ConstantValue = nullptr; // Non-null for CONSTANT; no storage.
+    unsigned ScopeID = 0;
 };
 
 class TypeSystem {