Handle closures that are invalid for Aleo.

In particular,

1. Insert a dummy instruction for empty closures
and finalizers. SnarkVM won't parse these with no instructions.

2. Give an error for Leo functions with
no parameters (rather than just generating
an invalid Aleo closure).

Fixes #28401

compiler/passes/src/code_generation/visit_program.rs

@@ -222,6 +222,14 @@ impl<'a> CodeGenerator<'a> {
 
         //  Construct and append the function body.
         let block_string = self.visit_block(&function.block);
+        if matches!(self.variant.unwrap(), Variant::Function | Variant::AsyncFunction)
+            && block_string.lines().all(|line| line.starts_with("    output "))
+        {
+            // There are no real instructions, which is invalid in Aleo, so
+            // add a dummy instruction.
+            function_string.push_str("    assert.eq true true;\n");
+        }
+
         function_string.push_str(&block_string);
 
         function_string

compiler/passes/src/type_checking/check_program.rs

@@ -263,11 +263,6 @@ impl<'a, N: Network> ProgramVisitor<'a> for TypeChecker<'a, N> {
         self.check_function_signature(function);
 
         if self.scope_state.variant == Some(Variant::AsyncFunction) {
-            // Async functions cannot have empty blocks
-            if function.block.statements.is_empty() {
-                self.emit_err(TypeCheckerError::finalize_block_must_not_be_empty(function.block.span));
-            }
-
             // Initialize the list of input futures. Each one must be awaited before the end of the function.
             self.await_checker.set_futures(
                 function
@@ -280,6 +275,10 @@ impl<'a, N: Network> ProgramVisitor<'a> for TypeChecker<'a, N> {
             );
         }
 
+        if function.variant == Variant::Function && function.input.is_empty() {
+            self.emit_err(TypeCheckerError::empty_function_arglist(function.span));
+        }
+
         self.visit_block(&function.block);
 
         // If the function has a return type, then check that it has a return.

errors/src/errors/parser/parser_errors.rs

@@ -73,7 +73,7 @@ create_messages!(
     }
 
     /// For when the parser encountered a mix of commas and semi-colons in struct member variables.
-    // TODO unused
+    // TODO This error is unused. Remove it in a future version.
     @formatted
     mixed_commas_and_semicolons {
         args: (),

errors/src/errors/type_checker/type_checker_error.rs

@@ -340,6 +340,7 @@ create_messages!(
         help: None,
     }
 
+    // TODO This error is unused. Remove it in a future version.
     @formatted
     finalize_block_must_not_be_empty {
         args: (),
@@ -886,4 +887,11 @@ create_messages!(
         msg: "A struct must have at least one member.".to_string(),
         help: None,
     }
+
+    @formatted
+    empty_function_arglist {
+        args: (),
+        msg: format!("Cannot define a function with no parameters."),
+        help: None,
+    }
 );

tests/expectations/compiler/finalize/empty_finalize.out

@@ -0,0 +1,16 @@
+namespace = "Compile"
+expectation = "Pass"
+outputs = [[{ compile = [{ initial_symbol_table = "1594125e96833cb52afcad4c876e44d61b2944a6c146e019b23fa0ad5d39db2a", type_checked_symbol_table = "95d8ce7541440d2568f633e1b7800d3d5d06e1147642eec802bfca4a9115e61c", unrolled_symbol_table = "95d8ce7541440d2568f633e1b7800d3d5d06e1147642eec802bfca4a9115e61c", initial_ast = "45d32cf0414a246717747dc917b07ffe55ff7587589d4c494479e18667e61a03", unrolled_ast = "45d32cf0414a246717747dc917b07ffe55ff7587589d4c494479e18667e61a03", ssa_ast = "eb6eff57864e407c245edbba3ab2949a2536643b3b864a8a42b65c348523a31f", flattened_ast = "6e8cc40e042029b3124b7b9a7e66905525207fb6cf0bfe5b71abfecbf10d7c72", destructured_ast = "22c2d4f79894ead71296929de2982b8289e2b43f7d83dc497a1be4532945ea17", inlined_ast = "e18c2f95e617c4c42c2359ea8a09924311f89c0c3a0bfa1e2ffe23c6ff933846", dce_ast = "e18c2f95e617c4c42c2359ea8a09924311f89c0c3a0bfa1e2ffe23c6ff933846", bytecode = """
+program test.aleo;
+
+function mint_public:
+    input r0 as address.public;
+    input r1 as u64.public;
+    async mint_public r0 r1 into r2;
+    output r2 as test.aleo/mint_public.future;
+
+finalize mint_public:
+    input r0 as address.public;
+    input r1 as u64.public;
+    assert.eq true true;
+""", errors = "", warnings = "" }] }]]

tests/expectations/compiler/function/empty_arglist_fail.out

@@ -0,0 +1,18 @@
+namespace = "Compile"
+expectation = "Fail"
+outputs = ["""
+Error [ETYC0372113]: Cannot define a function with no parameters.
+    --> compiler-test:4:5
+     |
+   4 |     function x() -> u8 {
+   5 |         return 0u8;
+   6 |     }
+     |     ^
+Error [ETYC0372083]: A program must have at least one transition function.
+    --> compiler-test:1:1
+     |
+   1 | 
+   2 | 
+   3 | program test.aleo {
+     | ^^^^^^^^^^^^
+"""]

tests/expectations/compiler/function/empty_function.out

@@ -0,0 +1,15 @@
+namespace = "Compile"
+expectation = "Pass"
+outputs = [[{ compile = [{ initial_symbol_table = "4ccc1709fb6b2aad9ee9a247bb37098d9330087d64e14af2a5c064287f701105", type_checked_symbol_table = "979420a8fc4bfbc81aeabe709704af919277f62699a09b0858c37544622a725a", unrolled_symbol_table = "979420a8fc4bfbc81aeabe709704af919277f62699a09b0858c37544622a725a", initial_ast = "52950f91033f987381d1b9a5ff69b626a8911d003da7edb503e97bd6e6637d2c", unrolled_ast = "52950f91033f987381d1b9a5ff69b626a8911d003da7edb503e97bd6e6637d2c", ssa_ast = "5314cb0ebd490a53c7ded487668632260992a4f49a10f1e247980b5c6647ad22", flattened_ast = "85fd8c8ed0cae4cd4b711d8d909d5aec0a176028fa91452fae92fbe5f6091f63", destructured_ast = "fc6b028060914573cc2c1885155f4f2bb5c90ed03caf720bff4d5b05eb299327", inlined_ast = "6b8711898970669f70badb94f5ce2abd87be07fbb764523dd2d9e6d94336e7cd", dce_ast = "6b8711898970669f70badb94f5ce2abd87be07fbb764523dd2d9e6d94336e7cd", bytecode = """
+program test.aleo;
+
+closure x:
+    input r0 as boolean;
+    assert.eq true true;
+    output 0u8 as u8;
+
+function t:
+    input r0 as boolean.private;
+    call x r0 into r1;
+    output r1 as u8.private;
+""", errors = "", warnings = "" }] }]]

tests/expectations/compiler/tuple/tuple_not_allowed_fail.out

@@ -12,10 +12,10 @@ Error [ETYC0372051]: A function cannot take in a tuple as input.
    8 |     function foo(a: (u8, u16)) -> (u8, u16) {
      |                  ^
 Error [ETYC0372049]: A tuple type cannot contain a tuple.
-    --> compiler-test:12:28
+    --> compiler-test:12:36
      |
-  12 |     function bar() -> (u8, (u16, u32)) {
-     |                            ^^^^^^^^^^
+  12 |     function bar(zz: bool) -> (u8, (u16, u32)) {
+     |                                    ^^^^^^^^^^
 Error [ETYC0372052]: A tuple expression cannot contain another tuple expression.
     --> compiler-test:13:22
      |

tests/tests/compiler/core/algorithms/pedersen_fail.leo

@@ -4,7 +4,7 @@ expectation = "Fail"
 */
 
 program test.aleo {    
-    function main() -> bool {
+    function main(zz: bool) -> bool {
         let a: group = Pedersen64::hash_to_field(1u128); // Pedersen64 hash_to_field returns a field type
 
         return true;

tests/tests/compiler/field/no_space_between_literal.leo

@@ -4,6 +4,6 @@ expectation = "Fail"
 */
 
 program test.aleo {    
-    function main() {
+    function main(x: bool) {
       let f = 1 field;
     }}

tests/tests/compiler/finalize/empty_finalize_fail.leo → tests/tests/compiler/finalize/empty_finalize.leo

@@ -1,6 +1,6 @@
 /*
 namespace = "Compile"
-expectation = "Fail"
+expectation = "Pass"
 */
 
 program test.aleo {    

tests/tests/compiler/function/empty_arglist_fail.leo

@@ -0,0 +1,10 @@
+/*
+namespace = "Compile"
+expectation = "Fail"
+*/
+
+program test.aleo {
+    function x() -> u8 {
+        return 0u8;
+    }
+}

tests/tests/compiler/function/empty_function.leo

@@ -0,0 +1,16 @@
+/*
+namespace = "Compile"
+expectation = "Pass"
+*/
+
+program test.aleo {
+    // This should pass and insert
+    // a dummy instruction into the empty function.
+    function x(a: bool) -> u8 {
+        return 0u8;
+    }
+
+    transition t(a: bool) -> u8 {
+        return x(a);
+    }
+}

tests/tests/compiler/function/undefined_fail.leo

@@ -4,7 +4,7 @@ expectation = "Fail"
 */
 
 program test.aleo {    
-    function main() -> u8 {
+    function main(zz: bool) -> u8 {
         my_function();
         return 0u8;
     }

tests/tests/compiler/group/no_space_between_literal.leo

@@ -4,7 +4,7 @@ expectation = "Fail"
 */
 
 program test.aleo {    
-    function main() -> group {
+    function main(x: bool) -> group {
       let g: group = (0,1) group;
       return g;
     }}

tests/tests/compiler/integers/i128/max_fail.leo

@@ -4,7 +4,7 @@ expectation = "Fail"
 */
 
 program test.aleo {    
-    function main() {
+    function main(x: bool) {
         let a: i128 = 170141183460469231731687303715884105728i128;
     }
 }

tests/tests/compiler/integers/i128/no_space_between_literal.leo

@@ -4,7 +4,7 @@ expectation = "Fail"
 */
 
 program test.aleo {    
-    function main() {
+    function main(x: bool) {
         let i = 1 i128;
     }
 }

tests/tests/compiler/integers/i16/no_space_between_literal.leo

@@ -4,7 +4,7 @@ expectation = "Fail"
 */
 
 program test.aleo {    
-    function main() {
+    function main(x: bool) {
         let i = 1 i16;
     }
 }

tests/tests/compiler/integers/i32/max_fail.leo

@@ -4,7 +4,7 @@ expectation = "Fail"
 */
 
 program test.aleo {    
-    function main() {
+    function main(x: bool) {
         let a: i32 = 2147483648i32;
     }
 }

tests/tests/compiler/integers/i32/no_space_between_literal.leo

@@ -4,7 +4,7 @@ expectation = "Fail"
 */
 
 program test.aleo {    
-    function main() {
+    function main(x: bool) {
         let i = 1 i32;
     }
 }

tests/tests/compiler/integers/i64/max_fail.leo

@@ -4,7 +4,7 @@ expectation = "Fail"
 */
 
 program test.aleo {    
-    function main() {
+    function main(x: bool) {
         let a: i64 = 9223372036854775808i64;
     }
 }

tests/tests/compiler/integers/i64/no_space_between_literal.leo

@@ -4,7 +4,7 @@ expectation = "Fail"
 */
 
 program test.aleo {    
-    function main() {
+    function main(x: bool) {
         let i = 1 i64;
     }
 }

tests/tests/compiler/integers/i8/max_fail.leo

@@ -4,6 +4,6 @@ expectation = "Fail"
 */
 
 program test.aleo {    
-    function main() {
+    function main(x: bool) {
         let a: i8 = 128i8;
     }}

tests/tests/compiler/integers/i8/no_space_between_literal.leo

@@ -4,7 +4,7 @@ expectation = "Fail"
 */
 
 program test.aleo {    
-    function main() {
+    function main(x: bool) {
         let i = 1 i8;
     }
 }

tests/tests/compiler/integers/u128/hex_min_fail.leo

@@ -4,7 +4,7 @@ expectation = "Fail"
 */
 
 program test.aleo {    
-    function main() {
+    function main(x: bool) {
         let a: u128 = -0x1u128;
     }
 }

tests/tests/compiler/integers/u128/max_fail.leo

@@ -4,7 +4,7 @@ expectation = "Fail"
 */
 
 program test.aleo {    
-    function main() {
+    function main(x: bool) {
         let a: u128 = 340282366920938463463374607431768211456u128;
     }
 }

tests/tests/compiler/integers/u128/min_fail.leo

@@ -4,7 +4,7 @@ expectation = "Fail"
 */
 
 program test.aleo {    
-    function main() {
+    function main(x: bool) {
         let a: u128 = -1u128;
     }
 }

tests/tests/compiler/integers/u128/no_space_between_literal.leo

@@ -4,7 +4,7 @@ expectation = "Fail"
 */
 
 program test.aleo {    
-    function main() {
+    function main(x: bool) {
         let i = 1 u128;
     }
 }

tests/tests/compiler/integers/u16/hex_min_fail.leo

@@ -4,7 +4,7 @@ expectation = "Fail"
 */
 
 program test.aleo {    
-    function main() {
+    function main(x: bool) {
         let a: u16 = -0x1u16;
     }
 }

tests/tests/compiler/integers/u16/max_fail.leo

@@ -4,7 +4,7 @@ expectation = "Fail"
 */
 
 program test.aleo {    
-    function main() {
+    function main(x: bool) {
         let a: u16 = 65536u16;
     }
 }

tests/tests/compiler/integers/u16/min_fail.leo

@@ -4,7 +4,7 @@ expectation = "Fail"
 */
 
 program test.aleo {    
-    function main() {
+    function main(x: bool) {
         let a: u16 = -1u16;
     }
 }

tests/tests/compiler/integers/u16/no_space_between_literal.leo

@@ -4,7 +4,7 @@ expectation = "Fail"
 */
 
 program test.aleo {    
-    function main() {
+    function main(x: bool) {
         let i = 1 u16;
     }
 }

tests/tests/compiler/integers/u32/hex_min_fail.leo

@@ -4,7 +4,7 @@ expectation = "Fail"
 */
 
 program test.aleo {    
-    function main() {
+    function main(x: bool) {
         let a: u32 = -0x1u32;
     }
 }