From 72ab6396999d7210db18cdbd08c80a402d6baaa8 Mon Sep 17 00:00:00 2001
From: Zachary Snow <zach@zachjs.com>
Date: Fri, 23 Dec 2022 19:55:44 -0700
Subject: [PATCH] forbid non-void return inside void functions

---
 src/Convert/Jump.hs            | 9 +++++----
 test/error/return_task.sv      | 7 +++++++
 test/error/return_void_func.sv | 7 +++++++
 3 files changed, 19 insertions(+), 4 deletions(-)
 create mode 100644 test/error/return_task.sv
 create mode 100644 test/error/return_void_func.sv

diff --git a/src/Convert/Jump.hs b/src/Convert/Jump.hs
index 85e64fb..3035330 100644
--- a/src/Convert/Jump.hs
+++ b/src/Convert/Jump.hs
@@ -41,7 +41,9 @@ convertModuleItem :: ModuleItem -> ModuleItem
 convertModuleItem (MIPackageItem (Function ml t f decls stmtsOrig)) =
     MIPackageItem $ Function ml t f decls' stmts''
     where
-        stmts = map (traverseNestedStmts convertReturn) stmtsOrig
+        stmts = if t == Void
+                then stmtsOrig
+                else map (traverseNestedStmts convertReturn) stmtsOrig
         convertReturn :: Stmt -> Stmt
         convertReturn (Return Nil) = Return Nil
         convertReturn (Return e) =
@@ -223,11 +225,12 @@ convertStmt (Break) = do
     assertMsg jumpAllowed "encountered break inside fork-join"
     modify $ \s -> s { sHasJump = True }
     return $ asgn jumpState jsBreak
-convertStmt (Return Nil) = do
+convertStmt (Return e) = do
     jumpAllowed <- gets sJumpAllowed
     returnAllowed <- gets sReturnAllowed
     assertMsg jumpAllowed "encountered return inside fork-join"
     assertMsg returnAllowed "encountered return outside of task or function"
+    assertMsg (e == Nil) "non-void return inside task or void function"
     modify $ \s -> s { sHasJump = True }
     return $ asgn jumpState jsReturn
 
@@ -253,8 +256,6 @@ convertStmt (Timing timing stmt) =
 convertStmt (StmtAttr attr stmt) =
     convertStmt stmt >>= return . StmtAttr attr
 
-convertStmt (Return{}) = return $
-    error "non-void return should have been elaborated already"
 convertStmt (Foreach{}) = return $
     error "foreach should have been elaborated already"
 
diff --git a/test/error/return_task.sv b/test/error/return_task.sv
new file mode 100644
index 0000000..3f61dba
--- /dev/null
+++ b/test/error/return_task.sv
@@ -0,0 +1,7 @@
+// pattern: non-void return inside task or void function
+module top;
+    task t;
+        return 1;
+    endtask
+    initial t;
+endmodule
diff --git a/test/error/return_void_func.sv b/test/error/return_void_func.sv
new file mode 100644
index 0000000..57db39a
--- /dev/null
+++ b/test/error/return_void_func.sv
@@ -0,0 +1,7 @@
+// pattern: non-void return inside task or void function
+module top;
+    function void f;
+        return 1;
+    endfunction
+    initial f;
+endmodule