feat: implement CIE 9.1 text file handling (OPENFILE/READFILE/WRITEFILE/CLOSEFILE/EOF)

Front end: OPENFILE/READFILE/WRITEFILE/CLOSEFILE plus reserved mode
keywords READ/WRITE/APPEND (RANDOM reserved with a dedicated
not-implemented error); statement nodes in new FileAST.h, parsing in new
ParserFile.cc; EOF joins the Builtins table as the 12th builtin and
CallExprAST now carries a line number for its runtime diagnostics.

Runtime: new FileHandler (StringHandler-shaped leaf) lazily synthesizes
internal __cps_file_* helper functions and a 16-slot open-file table
keyed by filename content (strcmp — STRING '=' is pointer identity).
EOF is an fgetc/ungetc peek; READFILE grows a malloc/realloc line buffer
and strips a trailing CR; fopen uses text modes so mingw-w64 line
translation works. File-free programs get byte-identical IR. All misuse
(not open, wrong mode, reopen, fopen failure, read past EOF, table full)
dies with the existing "[Fatal] line N:" pattern via a new
RuntimeCheck::emitErrorAndExit overload taking runtime printf args.

Also fixes a pre-existing ArithmeticHandler hole surfaced by adversarial
review: mixed-width integer operands (i1 BOOLEAN / i8 CHAR vs i64) now
widen via ZExt instead of emitting invalid IR, and remaining type
mismatches get a clean diagnostic; -EOF(f) and -IS_NUM(x) compile.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

2 files changed, 106 insertions, 1 deletions

diff --git a/lib/Parser/Parser.cc b/lib/Parser/Parser.cc
index 77df9bb..e67dda7 100644
--- a/lib/Parser/Parser.cc
+++ b/lib/Parser/Parser.cc
@@ -59,7 +59,7 @@ std::unique_ptr<ExprAST> Parser::ParseIdentifierExpr() {
         getNextToken();
         auto Args = ParseExprList(')', true);
         if (!Args) return nullptr;
-        return std::make_unique<CallExprAST>(IdName, std::move(*Args));
+        return std::make_unique<CallExprAST>(IdName, std::move(*Args), Line);
     }
 
     if (CurTok == '[') {
@@ -213,6 +213,7 @@ void Parser::syncToStatementStart() {
         case tok_function: case tok_procedure: case tok_call: case tok_return:
         case tok_else: case tok_endif: case tok_endwhile: case tok_until:
         case tok_next: case tok_endfunction: case tok_endprocedure:
+        case tok_openfile: case tok_readfile: case tok_writefile: case tok_closefile:
             return;
         default:
             getNextToken();
@@ -537,6 +538,18 @@ std::unique_ptr<StmtAST> Parser::ParseStatementImpl() {
     else if (CurTok == tok_return) {
         return ParseReturnStmt();
     }
+    else if (CurTok == tok_openfile) {
+        return ParseOpenFile();
+    }
+    else if (CurTok == tok_readfile) {
+        return ParseReadFile();
+    }
+    else if (CurTok == tok_writefile) {
+        return ParseWriteFile();
+    }
+    else if (CurTok == tok_closefile) {
+        return ParseCloseFile();
+    }
 
     fprintf(stderr, "Error: Unexpected token at line %d when expecting a statement\n", Lex.getLine());
     getNextToken(); // guarantee progress so error recovery cannot loop forever
diff --git a/lib/Parser/ParserFile.cc b/lib/Parser/ParserFile.cc
new file mode 100644
index 0000000..6fd368c
--- /dev/null
+++ b/lib/Parser/ParserFile.cc
@@ -0,0 +1,92 @@
+#include "cps/Parser.h"
+#include "cps/FileAST.h"
+#include <cstdio>
+
+using namespace cps;
+
+// OPENFILE <expr> FOR READ|WRITE|APPEND
+std::unique_ptr<StmtAST> Parser::ParseOpenFile() {
+    int Line = Lex.getLine();
+    getNextToken(); // eat OPENFILE
+
+    auto FileName = ParseExpression();
+    if (!FileName) return nullptr;
+
+    if (CurTok != tok_for) {
+        fprintf(stderr, "Error: Expected FOR after OPENFILE filename at line %d\n", Lex.getLine());
+        return nullptr;
+    }
+    getNextToken(); // eat FOR
+
+    FileMode Mode;
+    switch (CurTok) {
+    case tok_read:   Mode = FileMode::Read;   break;
+    case tok_write:  Mode = FileMode::Write;  break;
+    case tok_append: Mode = FileMode::Append; break;
+    case tok_random:
+        fprintf(stderr, "Error: File mode RANDOM is not implemented (text files only) at line %d\n",
+                Lex.getLine());
+        return nullptr;
+    default:
+        fprintf(stderr, "Error: Expected file mode READ, WRITE or APPEND at line %d\n", Lex.getLine());
+        return nullptr;
+    }
+    getNextToken(); // eat the mode keyword
+
+    return std::make_unique<OpenFileStmtAST>(std::move(FileName), Mode, Line);
+}
+
+// READFILE <expr>, <identifier>
+std::unique_ptr<StmtAST> Parser::ParseReadFile() {
+    int Line = Lex.getLine();
+    getNextToken(); // eat READFILE
+
+    auto FileName = ParseExpression();
+    if (!FileName) return nullptr;
+
+    if (CurTok != ',') {
+        fprintf(stderr, "Error: Expected ',' after READFILE filename at line %d\n", Lex.getLine());
+        return nullptr;
+    }
+    getNextToken(); // eat ','
+
+    if (CurTok != tok_identifier) {
+        fprintf(stderr, "Error: Expected variable name after ',' in READFILE at line %d\n", Lex.getLine());
+        return nullptr;
+    }
+    std::string VarName = Lex.IdentifierStr;
+    getNextToken(); // eat the variable name
+
+    return std::make_unique<ReadFileStmtAST>(std::move(FileName), VarName, Line);
+}
+
+// WRITEFILE <expr>, <expr>
+std::unique_ptr<StmtAST> Parser::ParseWriteFile() {
+    int Line = Lex.getLine();
+    getNextToken(); // eat WRITEFILE
+
+    auto FileName = ParseExpression();
+    if (!FileName) return nullptr;
+
+    if (CurTok != ',') {
+        fprintf(stderr, "Error: Expected ',' after WRITEFILE filename at line %d\n", Lex.getLine());
+        return nullptr;
+    }
+    getNextToken(); // eat ','
+
+    auto Data = ParseExpression();
+    if (!Data) return nullptr;
+
+    return std::make_unique<WriteFileStmtAST>(std::move(FileName), std::move(Data), Line);
+}
+
+// CLOSEFILE <expr>
+std::unique_ptr<StmtAST> Parser::ParseCloseFile() {
+    int Line = Lex.getLine();
+    getNextToken(); // eat CLOSEFILE
+
+    auto FileName = ParseExpression();
+    if (!FileName) return nullptr;
+
+    return std::make_unique<CloseFileStmtAST>(std::move(FileName), Line);
+}