From 9ca2e336eb7cb18600e18473fa5a9feb27d7a289 Mon Sep 17 00:00:00 2001
From: Edgar Luque <git@edgarluque.com>
Date: Tue, 12 Mar 2024 13:03:35 +0100
Subject: [PATCH] improv cast

---
 lib/edlang_ast/src/lib.rs              |  2 +-
 lib/edlang_codegen_llvm/src/codegen.rs |  4 ++--
 lib/edlang_ir/src/lib.rs               |  2 +-
 lib/edlang_lowering/src/lib.rs         | 29 +++++++++++++++++++++++---
 lib/edlang_parser/src/grammar.lalrpop  |  2 +-
 5 files changed, 31 insertions(+), 8 deletions(-)

diff --git a/lib/edlang_ast/src/lib.rs b/lib/edlang_ast/src/lib.rs
index ef92d59e3..f28de1556 100644
--- a/lib/edlang_ast/src/lib.rs
+++ b/lib/edlang_ast/src/lib.rs
@@ -176,7 +176,7 @@ pub enum Expression {
     Binary(Box<Self>, BinaryOp, Box<Self>),
     Deref(Box<Self>, Span),
     AsRef(Box<Self>, bool, Span),
-    Cast(PathExpr, Type, Span),
+    Cast(Box<Self>, Type, Span),
 }
 
 #[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
diff --git a/lib/edlang_codegen_llvm/src/codegen.rs b/lib/edlang_codegen_llvm/src/codegen.rs
index 9b2839c96..900297461 100644
--- a/lib/edlang_codegen_llvm/src/codegen.rs
+++ b/lib/edlang_codegen_llvm/src/codegen.rs
@@ -1033,7 +1033,7 @@ fn compile_rvalue<'ctx>(
             );
             compile_unary_op(ctx, fn_id, locals, *op, value)?
         }
-        ir::RValue::Cast(place, target_ty, span) => {
+        ir::RValue::Cast(op, target_ty, span) => {
             ctx.set_debug_loc(
                 ctx.builder
                     .get_current_debug_location()
@@ -1044,7 +1044,7 @@ fn compile_rvalue<'ctx>(
 
             let target_ty = target_ty.clone();
             let target_llvm_ty = compile_basic_type(ctx, &target_ty);
-            let (value, ty) = compile_load_place(ctx, fn_id, locals, place, false)?;
+            let (value, ty) = compile_load_operand(ctx, fn_id, locals, op)?;
             let current_ty = compile_basic_type(ctx, &ty);
 
             if target_llvm_ty.is_pointer_type() {
diff --git a/lib/edlang_ir/src/lib.rs b/lib/edlang_ir/src/lib.rs
index 1a92c3fc7..54f81eb1d 100644
--- a/lib/edlang_ir/src/lib.rs
+++ b/lib/edlang_ir/src/lib.rs
@@ -419,7 +419,7 @@ pub enum RValue {
     BinOp(BinOp, Operand, Operand, Span),
     LogicOp(LogicalOp, Operand, Operand, Span),
     UnOp(UnOp, Operand, Span),
-    Cast(Place, TypeInfo, Span),
+    Cast(Operand, TypeInfo, Span),
 }
 
 #[derive(Debug, Clone)]
diff --git a/lib/edlang_lowering/src/lib.rs b/lib/edlang_lowering/src/lib.rs
index 115cef43d..31a9ddcc1 100644
--- a/lib/edlang_lowering/src/lib.rs
+++ b/lib/edlang_lowering/src/lib.rs
@@ -735,14 +735,37 @@ fn lower_expr(
 
             (RValue::Use(Operand::Move(place), info.span), ty, info.span)
         }
-        ast::Expression::Cast(path, cast_ty, span) => {
-            let (place, _ty, _path_span) = lower_path(builder, path)?;
+        ast::Expression::Cast(exp, cast_ty, span) => {
+            let (value, ty, _exp_span) = lower_expr(builder, exp, None)?;
             let new_ty = lower_type(&builder.ctx, cast_ty, builder.local_module)?;
             let kind = new_ty.kind.clone();
 
             // todo: some checks?
 
-            (RValue::Cast(place, new_ty, *span), kind, *span)
+            // check if its a use directly, to avoid a temporary.
+            let rvalue = match value {
+                RValue::Use(op, _) => RValue::Cast(op, new_ty.clone(), *span),
+                value => {
+                    let inner_local = builder.add_local(Local::temp(ty.clone()));
+                    let inner_place = Place {
+                        local: inner_local,
+                        projection: Default::default(),
+                    };
+
+                    builder.statements.push(Statement {
+                        span: None,
+                        kind: StatementKind::StorageLive(inner_local),
+                    });
+
+                    builder.statements.push(Statement {
+                        span: None,
+                        kind: StatementKind::Assign(inner_place.clone(), value),
+                    });
+                    RValue::Cast(Operand::Move(inner_place), new_ty.clone(), *span)
+                }
+            };
+
+            (rvalue, kind, *span)
         }
     })
 }
diff --git a/lib/edlang_parser/src/grammar.lalrpop b/lib/edlang_parser/src/grammar.lalrpop
index 46656462c..d564dd150 100644
--- a/lib/edlang_parser/src/grammar.lalrpop
+++ b/lib/edlang_parser/src/grammar.lalrpop
@@ -343,7 +343,7 @@ pub(crate) Expression: ast::Expression = {
     Box::new(rhs)
   ),
   #[precedence(level="5")] #[assoc(side="left")]
-  <lo:@L> <a:PathExpr> "as" <b: Type> <hi:@R> => ast::Expression::Cast(a, b, ast::Span::new(lo, hi)),
+  <lo:@L> <a:Expression> "as" <b: Type> <hi:@R> => ast::Expression::Cast(Box::new(a), b, ast::Span::new(lo, hi)),
   "(" <StructInitExpr> ")" => ast::Expression::StructInit(<>),
 }