feat(codegen)!: require explicit REAL to INTEGER conversion and add INT

Implicit REAL to INTEGER is now a compile error with an INT(...) hint.
INT is a compiler builtin that truncates toward zero and raises a runtime
error for NaN or values outside the INTEGER range.

No existing test program relied on the implicit conversion.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

3 files changed, 30 insertions, 2 deletions

diff --git a/lib/CodeGen/Builtins.h b/lib/CodeGen/Builtins.h
index 2163b3e..84ba765 100644
--- a/lib/CodeGen/Builtins.h
+++ b/lib/CodeGen/Builtins.h
@@ -18,6 +18,7 @@ inline constexpr BuiltinInfo Builtins[] = {
     {"MALLOC",     1, "C_TYPE(\"void*\")"},
     {"REALLOC",    2, "C_TYPE(\"void*\")"},
     {"FREE",       1, "C_TYPE(\"void*\")"},
+    {"INT",        1, "INTEGER"},
 };
 
 inline const BuiltinInfo *findBuiltin(const std::string &Name) {
diff --git a/lib/CodeGen/ExpressionGen.cc b/lib/CodeGen/ExpressionGen.cc
index 0434348..51d7087 100644
--- a/lib/CodeGen/ExpressionGen.cc
+++ b/lib/CodeGen/ExpressionGen.cc
@@ -251,6 +251,7 @@ Value *CodeGen::emitCall(const std::string &Callee,
         if (!Address) return nullptr;
         return Memory->emitRelease(Address, Line);
     }
+    if (Name == "INT") return emitIntBuiltin(ArgExprs[0].get(), Line);
     if (Name == "EOF") {
         Value *FileName = emitFileNameOperand(ArgExprs[0].get(), "EOF");
         if (!FileName) return nullptr;
@@ -264,6 +265,30 @@ Value *CodeGen::emitCall(const std::string &Callee,
     return FuncGen->emitCall(*Sig, Args, Variadic);
 }
 
+// INT(x): the integer part of a REAL, truncated toward zero. NaN and values
+// outside the INTEGER range are a runtime error.
+Value *CodeGen::emitIntBuiltin(ExprAST *Arg, int Line) {
+    SaveAndRestore<int> Location(DiagnosticLine, Line ? Line : DiagnosticLine);
+    const TypeInfo *Info = getExprTypeInfo(Arg);
+    if (isWholeArrayVar(Arg) || !Info ||
+        (Info->Kind != TypeKind::Integer && Info->Kind != TypeKind::Real)) {
+        reportError("INT expects an INTEGER or REAL argument");
+        return nullptr;
+    }
+    Value *V = emitExpr(Arg);
+    if (!V || Info->Kind == TypeKind::Integer) return V;
+
+    Type *DoubleTy = Type::getDoubleTy(*TheContext);
+    Value *AtLeastMin = Builder->CreateFCmpOGE(V, ConstantFP::get(DoubleTy, -9223372036854775808.0), "int_ge_min");
+    Value *BelowMax = Builder->CreateFCmpOLT(V, ConstantFP::get(DoubleTy, 9223372036854775808.0), "int_lt_max");
+    Value *InRange = Builder->CreateAnd(AtLeastMin, BelowMax, "int_in_range");
+    Value *OutOfRange = Builder->CreateNot(InRange, "int_out_of_range");
+    Value *Msg = Builder->CreateGlobalString("[Fatal] line %d: INT argument out of INTEGER range\n",
+                                             "err_int_range", 0, TheModule.get());
+    RuntimeChecker->emitCheck(OutOfRange, Msg, {RuntimeChecker->lineValue(Line)});
+    return Builder->CreateFPToSI(V, Type::getInt64Ty(*TheContext), "int_value");
+}
+
 Value *CodeGen::emitAllocationSize(ExprAST *Expr) {
     SaveAndRestore<int> Location(DiagnosticLine, Expr->getLine() ? Expr->getLine() : DiagnosticLine);
     const TypeInfo *Info = getExprTypeInfo(Expr);
diff --git a/lib/CodeGen/TypeCheckGen.cc b/lib/CodeGen/TypeCheckGen.cc
index 8d54221..7cdf6ea 100644
--- a/lib/CodeGen/TypeCheckGen.cc
+++ b/lib/CodeGen/TypeCheckGen.cc
@@ -109,8 +109,10 @@ Value *CodeGen::emitCoercedExpr(ExprAST *E, const TypeInfo *Target) {
         bool Allowed = Src->Kind == Target->Kind ||
                        (Src->Kind == TypeKind::Integer && Target->Kind == TypeKind::Real);
         if (!Allowed) {
-            reportError("Cannot use a value of type %s where %s is expected",
-                        Src->Name.c_str(), Target->Name.c_str());
+            reportError("Cannot use a value of type %s where %s is expected%s",
+                        Src->Name.c_str(), Target->Name.c_str(),
+                        Src->Kind == TypeKind::Real && Target->Kind == TypeKind::Integer
+                            ? " (use INT(...) to convert)" : "");
             return nullptr;
         }
     }