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Merged
nickna merged 1 commit into from
Jan 14, 2026
Merged

Enhance IL emission with validation and exception handling #6

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16 changes: 16 additions & 0 deletions Compilation/CompilationContext.cs
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Expand Up @@ -46,6 +46,12 @@ public class CompilationContext
public TypeMapper TypeMapper { get; }
public LocalsManager Locals { get; }

/// <summary>
/// Validated IL builder that wraps the ILGenerator with compile-time checks.
/// Use this for new code to catch label, stack, and exception block errors early.
/// </summary>
public ValidatedILBuilder ILBuilder { get; private set; }

/// <summary>
/// Type provider for resolving .NET types (runtime or reference assembly mode).
/// Use this instead of typeof() for type resolution to support --ref-asm compilation.
Expand Down Expand Up @@ -416,6 +422,16 @@ public CompilationContext(
Classes = classes;
Types = types ?? TypeProvider.Runtime;
Locals = new LocalsManager(il);
ILBuilder = new ValidatedILBuilder(il, Types);
}

/// <summary>
/// Updates the validated IL builder for a new ILGenerator (when switching methods).
/// Call this when the IL property changes to a new method's generator.
/// </summary>
public void UpdateILBuilder(ILGenerator newIL)
{
ILBuilder = new ValidatedILBuilder(newIL, Types);
}

public void DefineParameter(string name, int argIndex, Type? paramType = null)
Expand Down
21 changes: 11 additions & 10 deletions Compilation/ILCompiler.Classes.Methods.cs
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Expand Up @@ -683,8 +683,9 @@ private void EmitMethod(TypeBuilder typeBuilder, Stmt.Function method, FieldInfo
lockTakenLocal = il.DeclareLocal(typeof(bool)); // bool __lockTaken

// Set up deferred return handling for the lock's exception block
// Use the builder to define the label so it's tracked for validation
ctx.ReturnValueLocal = il.DeclareLocal(typeof(object));
ctx.ReturnLabel = il.DefineLabel();
ctx.ReturnLabel = ctx.ILBuilder.DefineLabel("lock_deferred_return");
ctx.ExceptionBlockDepth++;

// int __prevReentrancy = _lockReentrancy.Value;
Expand Down Expand Up @@ -719,8 +720,8 @@ private void EmitMethod(TypeBuilder typeBuilder, Stmt.Function method, FieldInfo

il.MarkLabel(skipEnterLabel);

// Begin try block
il.BeginExceptionBlock();
// Begin try block - use builder to keep exception depth in sync
ctx.ILBuilder.BeginExceptionBlock();
}

// Abstract methods have no body to emit
Expand All @@ -740,10 +741,10 @@ private void EmitMethod(TypeBuilder typeBuilder, Stmt.Function method, FieldInfo
// ReturnValueLocal is guaranteed non-null here (set up earlier in hasLock block)
il.Emit(OpCodes.Ldnull);
il.Emit(OpCodes.Stloc, ctx.ReturnValueLocal!);
il.Emit(OpCodes.Leave, ctx.ReturnLabel);
ctx.ILBuilder.Emit_Leave(ctx.ReturnLabel);

// Begin finally block
il.BeginFinallyBlock();
// Begin finally block - use builder for exception block tracking
ctx.ILBuilder.BeginFinallyBlock();

// _lockReentrancy.Value = __prevReentrancy;
il.Emit(OpCodes.Ldarg_0); // this
Expand All @@ -763,13 +764,13 @@ private void EmitMethod(TypeBuilder typeBuilder, Stmt.Function method, FieldInfo

il.MarkLabel(skipExitLabel);

// End try/finally block
il.EndExceptionBlock();
// End try/finally block - use builder for exception block tracking
ctx.ILBuilder.EndExceptionBlock();

ctx.ExceptionBlockDepth--;

// Mark return label and emit actual return
il.MarkLabel(ctx.ReturnLabel);
// Mark return label and emit actual return - use builder since label was defined with builder
ctx.ILBuilder.MarkLabel(ctx.ReturnLabel);
il.Emit(OpCodes.Ldloc, ctx.ReturnValueLocal!); // Non-null in hasLock path
il.Emit(OpCodes.Ret);
}
Expand Down
21 changes: 11 additions & 10 deletions Compilation/ILCompiler.Classes.Static.cs
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Expand Up @@ -221,8 +221,9 @@ private void EmitStaticMethodBody(string className, Stmt.Function method)
lockTakenLocal = il.DeclareLocal(typeof(bool)); // bool __lockTaken

// Set up deferred return handling for the lock's exception block
// Use the builder to define the label so it's tracked for validation
ctx.ReturnValueLocal = il.DeclareLocal(typeof(object));
ctx.ReturnLabel = il.DefineLabel();
ctx.ReturnLabel = ctx.ILBuilder.DefineLabel("static_lock_deferred_return");
ctx.ExceptionBlockDepth++;

// int __prevReentrancy = _staticLockReentrancy.Value;
Expand Down Expand Up @@ -254,8 +255,8 @@ private void EmitStaticMethodBody(string className, Stmt.Function method)

il.MarkLabel(skipEnterLabel);

// Begin try block
il.BeginExceptionBlock();
// Begin try block - use builder to keep exception depth in sync
ctx.ILBuilder.BeginExceptionBlock();
}

// Abstract methods have no body to emit
Expand All @@ -275,10 +276,10 @@ private void EmitStaticMethodBody(string className, Stmt.Function method)
// ReturnValueLocal is guaranteed non-null here (set up earlier in hasLock block)
il.Emit(OpCodes.Ldnull);
il.Emit(OpCodes.Stloc, ctx.ReturnValueLocal!);
il.Emit(OpCodes.Leave, ctx.ReturnLabel);
ctx.ILBuilder.Emit_Leave(ctx.ReturnLabel);

// Begin finally block
il.BeginFinallyBlock();
// Begin finally block - use builder for exception block tracking
ctx.ILBuilder.BeginFinallyBlock();

// _staticLockReentrancy.Value = __prevReentrancy;
il.Emit(OpCodes.Ldsfld, staticReentrancyField); // _staticLockReentrancy
Expand All @@ -296,13 +297,13 @@ private void EmitStaticMethodBody(string className, Stmt.Function method)

il.MarkLabel(skipExitLabel);

// End try/finally block
il.EndExceptionBlock();
// End try/finally block - use builder for exception block tracking
ctx.ILBuilder.EndExceptionBlock();

ctx.ExceptionBlockDepth--;

// Mark return label and emit actual return
il.MarkLabel(ctx.ReturnLabel);
// Mark return label and emit actual return - use builder since label was defined with builder
ctx.ILBuilder.MarkLabel(ctx.ReturnLabel);
il.Emit(OpCodes.Ldloc, ctx.ReturnValueLocal!); // Non-null in hasLock path
il.Emit(OpCodes.Ret);
}
Expand Down
19 changes: 10 additions & 9 deletions Compilation/ILEmitter.Calls.cs
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Expand Up @@ -731,19 +731,20 @@ private void EmitAmbiguousMethodCall(Expr obj, string methodName, List<Expr> arg
IL.Emit(OpCodes.Stloc, objLocal);

// Check if it's a string
var isStringLabel = IL.DefineLabel();
var isListLabel = IL.DefineLabel();
var doneLabel = IL.DefineLabel();
var builder = _ctx.ILBuilder;
var isStringLabel = builder.DefineLabel("ambiguous_string");
var isListLabel = builder.DefineLabel("ambiguous_list");
var doneLabel = builder.DefineLabel("ambiguous_done");

IL.Emit(OpCodes.Ldloc, objLocal);
IL.Emit(OpCodes.Isinst, _ctx.Types.String);
IL.Emit(OpCodes.Brtrue, isStringLabel);
builder.Emit_Brtrue(isStringLabel);

// Assume it's a list if not a string
IL.Emit(OpCodes.Br, isListLabel);
builder.Emit_Br(isListLabel);

// String path
IL.MarkLabel(isStringLabel);
builder.MarkLabel(isStringLabel);
IL.Emit(OpCodes.Ldloc, objLocal);
IL.Emit(OpCodes.Castclass, _ctx.Types.String);

Expand Down Expand Up @@ -811,10 +812,10 @@ private void EmitAmbiguousMethodCall(Expr obj, string methodName, List<Expr> arg
IL.Emit(OpCodes.Call, _ctx.Runtime!.StringConcat);
break;
}
IL.Emit(OpCodes.Br, doneLabel);
builder.Emit_Br(doneLabel);

// List path
IL.MarkLabel(isListLabel);
builder.MarkLabel(isListLabel);
IL.Emit(OpCodes.Ldloc, objLocal);
IL.Emit(OpCodes.Castclass, _ctx.Types.ListOfObject);

Expand Down Expand Up @@ -877,7 +878,7 @@ private void EmitAmbiguousMethodCall(Expr obj, string methodName, List<Expr> arg
break;
}

IL.MarkLabel(doneLabel);
builder.MarkLabel(doneLabel);
}

/// <summary>
Expand Down
20 changes: 11 additions & 9 deletions Compilation/ILEmitter.Expressions.cs
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Expand Up @@ -163,8 +163,9 @@ protected override void EmitSuper(Expr.Super s)

protected override void EmitTernary(Expr.Ternary t)
{
var elseLabel = IL.DefineLabel();
var endLabel = IL.DefineLabel();
var builder = _ctx.ILBuilder;
var elseLabel = builder.DefineLabel("ternary_else");
var endLabel = builder.DefineLabel("ternary_end");

EmitExpression(t.Condition);
// Handle condition based on what's actually on the stack
Expand All @@ -187,35 +188,36 @@ protected override void EmitTernary(Expr.Ternary t)
EnsureBoxed(); // Ensure it's boxed first
EmitTruthyCheck();
}
IL.Emit(OpCodes.Brfalse, elseLabel);
builder.Emit_Brfalse(elseLabel);

EmitExpression(t.ThenBranch);
EmitBoxIfNeeded(t.ThenBranch);
IL.Emit(OpCodes.Br, endLabel);
builder.Emit_Br(endLabel);

IL.MarkLabel(elseLabel);
builder.MarkLabel(elseLabel);
EmitExpression(t.ElseBranch);
EmitBoxIfNeeded(t.ElseBranch);

IL.MarkLabel(endLabel);
builder.MarkLabel(endLabel);
// Both branches box, so result is Unknown (boxed object)
SetStackUnknown();
}

protected override void EmitNullishCoalescing(Expr.NullishCoalescing nc)
{
var endLabel = IL.DefineLabel();
var builder = _ctx.ILBuilder;
var endLabel = builder.DefineLabel("nullish_end");

EmitExpression(nc.Left);
EmitBoxIfNeeded(nc.Left);
IL.Emit(OpCodes.Dup);
IL.Emit(OpCodes.Brtrue, endLabel);
builder.Emit_Brtrue(endLabel);

IL.Emit(OpCodes.Pop);
EmitExpression(nc.Right);
EmitBoxIfNeeded(nc.Right);

IL.MarkLabel(endLabel);
builder.MarkLabel(endLabel);
// Both branches box, so result is Unknown (boxed object)
SetStackUnknown();
}
Expand Down
31 changes: 17 additions & 14 deletions Compilation/ILEmitter.Helpers.cs
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Expand Up @@ -15,7 +15,8 @@ public void FinalizeReturns()
if (_ctx.ReturnValueLocal != null)
{
// Mark the return label and emit the actual return
IL.MarkLabel(_ctx.ReturnLabel);
// Use builder's MarkLabel since ReturnLabel was defined with builder
_ctx.ILBuilder.MarkLabel(_ctx.ReturnLabel);
IL.Emit(OpCodes.Ldloc, _ctx.ReturnValueLocal);
IL.Emit(OpCodes.Ret);
}
Expand All @@ -33,6 +34,7 @@ public void FinalizeReturns()
public void EmitDefaultParameters(List<Stmt.Parameter> parameters, bool isInstanceMethod)
{
int argOffset = isInstanceMethod ? 1 : 0;
var builder = _ctx.ILBuilder;

for (int i = 0; i < parameters.Count; i++)
{
Expand All @@ -42,18 +44,18 @@ public void EmitDefaultParameters(List<Stmt.Parameter> parameters, bool isInstan
int argIndex = i + argOffset;

// if (arg == null) { arg = <default>; }
var skipDefault = IL.DefineLabel();
var skipDefault = builder.DefineLabel($"skip_default_{i}");

// Load argument and check if null
IL.Emit(OpCodes.Ldarg, argIndex);
IL.Emit(OpCodes.Brtrue, skipDefault);
builder.Emit_Brtrue(skipDefault);

// Argument is null, emit default value and store
EmitExpression(param.DefaultValue);
EmitBoxIfNeeded(param.DefaultValue);
IL.Emit(OpCodes.Starg, argIndex);

IL.MarkLabel(skipDefault);
builder.MarkLabel(skipDefault);
}
}

Expand Down Expand Up @@ -296,35 +298,36 @@ protected override void EmitTruthyCheck()
// - null => false
// - boxed false => false
// - everything else => true
var checkBoolLabel = IL.DefineLabel();
var falseLabel = IL.DefineLabel();
var endLabel = IL.DefineLabel();
var builder = _ctx.ILBuilder;
var checkBoolLabel = builder.DefineLabel("truthy_checkbool");
var falseLabel = builder.DefineLabel("truthy_false");
var endLabel = builder.DefineLabel("truthy_end");

// Check for null
IL.Emit(OpCodes.Dup);
IL.Emit(OpCodes.Brfalse, falseLabel);
builder.Emit_Brfalse(falseLabel);

// Check if it's a boolean
IL.Emit(OpCodes.Dup);
IL.Emit(OpCodes.Isinst, _ctx.Types.Boolean);
IL.Emit(OpCodes.Brfalse, checkBoolLabel);
builder.Emit_Brfalse(checkBoolLabel);

// It's a boxed bool - unbox and use the value
IL.Emit(OpCodes.Unbox_Any, _ctx.Types.Boolean);
IL.Emit(OpCodes.Br, endLabel);
builder.Emit_Br(endLabel);

IL.MarkLabel(checkBoolLabel);
builder.MarkLabel(checkBoolLabel);
// Not null and not bool - always truthy
IL.Emit(OpCodes.Pop);
IL.Emit(OpCodes.Ldc_I4_1);
IL.Emit(OpCodes.Br, endLabel);
builder.Emit_Br(endLabel);

IL.MarkLabel(falseLabel);
builder.MarkLabel(falseLabel);
// Null - false
IL.Emit(OpCodes.Pop);
IL.Emit(OpCodes.Ldc_I4_0);

IL.MarkLabel(endLabel);
builder.MarkLabel(endLabel);
}

private static bool IsComparisonOp(TokenType op) =>
Expand Down
9 changes: 5 additions & 4 deletions Compilation/ILEmitter.Operators.cs
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Expand Up @@ -156,7 +156,8 @@ private bool IsComparisonExpr(Expr expr)

protected override void EmitLogical(Expr.Logical l)
{
var endLabel = IL.DefineLabel();
var builder = _ctx.ILBuilder;
var endLabel = builder.DefineLabel("logical_end");

EmitExpression(l.Left);
EmitBoxIfNeeded(l.Left);
Expand All @@ -166,19 +167,19 @@ protected override void EmitLogical(Expr.Logical l)
if (l.Operator.Type == TokenType.AND_AND)
{
// Short-circuit: if left is falsy, return left
IL.Emit(OpCodes.Brfalse, endLabel);
builder.Emit_Brfalse(endLabel);
}
else // OR
{
// Short-circuit: if left is truthy, return left
IL.Emit(OpCodes.Brtrue, endLabel);
builder.Emit_Brtrue(endLabel);
}

IL.Emit(OpCodes.Pop); // Pop the duplicate left value
EmitExpression(l.Right);
EmitBoxIfNeeded(l.Right);

IL.MarkLabel(endLabel);
builder.MarkLabel(endLabel);
SetStackUnknown(); // Logical operators return boxed object
}

Expand Down
13 changes: 7 additions & 6 deletions Compilation/ILEmitter.Properties.cs
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Expand Up @@ -162,21 +162,22 @@ protected override void EmitGet(Expr.Get g)

if (g.Optional)
{
var nullLabel = IL.DefineLabel();
var endLabel = IL.DefineLabel();
var builder = _ctx.ILBuilder;
var nullLabel = builder.DefineLabel("optional_null");
var endLabel = builder.DefineLabel("optional_end");

IL.Emit(OpCodes.Dup);
IL.Emit(OpCodes.Brfalse, nullLabel);
builder.Emit_Brfalse(nullLabel);

IL.Emit(OpCodes.Ldstr, g.Name.Lexeme);
IL.Emit(OpCodes.Call, _ctx.Runtime!.GetProperty);
IL.Emit(OpCodes.Br, endLabel);
builder.Emit_Br(endLabel);

IL.MarkLabel(nullLabel);
builder.MarkLabel(nullLabel);
IL.Emit(OpCodes.Pop);
IL.Emit(OpCodes.Ldnull);

IL.MarkLabel(endLabel);
builder.MarkLabel(endLabel);
}
else
{
Expand Down
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