From c83b0616e24eb41dab082724686919c184251548 Mon Sep 17 00:00:00 2001
From: Piotr Fusik <piotr@fusion-lang.org>
Date: Mon, 25 Mar 2024 11:47:47 +0100
Subject: [PATCH] [ctfe] Fix forward-referenced methods.

---
 AST.fu                     | 2 +-
 Sema.fu                    | 6 +++++-
 libfut.cpp                 | 8 ++++++--
 libfut.cs                  | 6 +++++-
 libfut.hpp                 | 2 +-
 libfut.js                  | 4 ++++
 test/ConstForwardMethod.fu | 9 +++++++++
 7 files changed, 31 insertions(+), 6 deletions(-)
 create mode 100644 test/ConstForwardMethod.fu

diff --git a/AST.fu b/AST.fu
index ec63b10d..3dc8936e 100644
--- a/AST.fu
+++ b/AST.fu
@@ -1198,7 +1198,7 @@ public class FuMethodBase : FuMember
 {
 	internal FuParameters() Parameters;
 	internal List<FuThrowsDeclaration#>() Throws;
-	internal FuStatement#? Body;
+	internal FuScope#? Body;
 	internal bool IsLive = false;
 	internal HashSet<FuMethod!>() Calls;
 	public override bool IsStatic() => false; // constructor
diff --git a/Sema.fu b/Sema.fu
index 132b32fa..70c0b23d 100644
--- a/Sema.fu
+++ b/Sema.fu
@@ -1357,7 +1357,7 @@ public class FuSema
 		symbol.Symbol = method;
 
 		if (method.CallType == FuCallType.Static
-		 && method.Body is FuReturn ret
+		 && method.Body is FuReturn! ret
 		 && arguments.All(arg => arg is FuLiteral)
 		 && !this.CurrentPureMethods.Contains(method)) {
 			this.CurrentPureMethods.Add(method);
@@ -1368,7 +1368,11 @@ public class FuSema
 				else
 					this.CurrentPureArguments[param] = param.Value;
 			}
+			FuScope! callSite = this.CurrentScope;
+			ret.Parent = method.Parameters;
+			this.CurrentScope = ret;
 			FuExpr# result = VisitExpr(ret.Value);
+			this.CurrentScope = callSite;
 			for (FuVar? param = method.FirstParameter(); param != null; param = param.NextVar())
 				this.CurrentPureArguments.Remove(param);
 			this.CurrentPureMethods.Remove(method);
diff --git a/libfut.cpp b/libfut.cpp
index 8afbe588..5c9b4104 100644
--- a/libfut.cpp
+++ b/libfut.cpp
@@ -5730,8 +5730,8 @@ std::shared_ptr<FuExpr> FuSema::resolveCallWithArguments(std::shared_ptr<FuCallE
 			reportError(expr.get(), std::format("Method marked 'throws {}' called from a method without it", exception->name));
 	}
 	symbol->symbol = method;
-	const FuReturn * ret;
-	if (method->callType == FuCallType::static_ && (ret = dynamic_cast<const FuReturn *>(method->body.get())) && std::all_of(arguments->begin(), arguments->end(), [](const std::shared_ptr<FuExpr> &arg) { return dynamic_cast<const FuLiteral *>(arg.get()); }) && !this->currentPureMethods.contains(method)) {
+	FuReturn * ret;
+	if (method->callType == FuCallType::static_ && (ret = dynamic_cast<FuReturn *>(method->body.get())) && std::all_of(arguments->begin(), arguments->end(), [](const std::shared_ptr<FuExpr> &arg) { return dynamic_cast<const FuLiteral *>(arg.get()); }) && !this->currentPureMethods.contains(method)) {
 		this->currentPureMethods.insert(method);
 		i = 0;
 		for (const FuVar * param = method->firstParameter(); param != nullptr; param = param->nextVar()) {
@@ -5740,7 +5740,11 @@ std::shared_ptr<FuExpr> FuSema::resolveCallWithArguments(std::shared_ptr<FuCallE
 			else
 				this->currentPureArguments[param] = param->value;
 		}
+		FuScope * callSite = this->currentScope;
+		ret->parent = &method->parameters;
+		this->currentScope = ret;
 		std::shared_ptr<FuExpr> result = visitExpr(ret->value);
+		this->currentScope = callSite;
 		for (const FuVar * param = method->firstParameter(); param != nullptr; param = param->nextVar())
 			this->currentPureArguments.erase(param);
 		this->currentPureMethods.erase(method);
diff --git a/libfut.cs b/libfut.cs
index c1525150..12910fca 100644
--- a/libfut.cs
+++ b/libfut.cs
@@ -2738,7 +2738,7 @@ public class FuMethodBase : FuMember
 
 		internal readonly List<FuThrowsDeclaration> Throws = new List<FuThrowsDeclaration>();
 
-		internal FuStatement Body;
+		internal FuScope Body;
 
 		internal bool IsLive = false;
 
@@ -5852,7 +5852,11 @@ FuExpr ResolveCallWithArguments(FuCallExpr expr, List<FuExpr> arguments)
 					else
 						this.CurrentPureArguments[param] = param.Value;
 				}
+				FuScope callSite = this.CurrentScope;
+				ret.Parent = method.Parameters;
+				this.CurrentScope = ret;
 				FuExpr result = VisitExpr(ret.Value);
+				this.CurrentScope = callSite;
 				for (FuVar param = method.FirstParameter(); param != null; param = param.NextVar())
 					this.CurrentPureArguments.Remove(param);
 				this.CurrentPureMethods.Remove(method);
diff --git a/libfut.hpp b/libfut.hpp
index 9db9ce34..ef3e26ec 100644
--- a/libfut.hpp
+++ b/libfut.hpp
@@ -1301,7 +1301,7 @@ class FuMethodBase : public FuMember
 public:
 	FuParameters parameters;
 	std::vector<std::shared_ptr<FuThrowsDeclaration>> throws;
-	std::shared_ptr<FuStatement> body;
+	std::shared_ptr<FuScope> body;
 	bool isLive = false;
 	std::unordered_set<FuMethod *> calls;
 };
diff --git a/libfut.js b/libfut.js
index 5188c080..19e4c829 100644
--- a/libfut.js
+++ b/libfut.js
@@ -6153,7 +6153,11 @@ export class FuSema
 				else
 					this.#currentPureArguments[param] = param.value;
 			}
+			let callSite = this.#currentScope;
+			ret.parent = method.parameters;
+			this.#currentScope = ret;
 			let result = this.#visitExpr(ret.value);
+			this.#currentScope = callSite;
 			for (let param = method.firstParameter(); param != null; param = param.nextVar())
 				delete this.#currentPureArguments[param];
 			this.#currentPureMethods.delete(method);
diff --git a/test/ConstForwardMethod.fu b/test/ConstForwardMethod.fu
new file mode 100644
index 00000000..923950fb
--- /dev/null
+++ b/test/ConstForwardMethod.fu
@@ -0,0 +1,9 @@
+public static class Test
+{
+	public static bool Run()
+	{
+		return Foo(42);
+	}
+
+	static bool Foo(int answer) => answer == 42;
+}