leo_passes/static_analysis/
visitor.rs

1// Copyright (C) 2019-2025 Provable Inc.
2// This file is part of the Leo library.
3
4// The Leo library is free software: you can redistribute it and/or modify
5// it under the terms of the GNU General Public License as published by
6// the Free Software Foundation, either version 3 of the License, or
7// (at your option) any later version.
8
9// The Leo library is distributed in the hope that it will be useful,
10// but WITHOUT ANY WARRANTY; without even the implied warranty of
11// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12// GNU General Public License for more details.
13
14// You should have received a copy of the GNU General Public License
15// along with the Leo library. If not, see <https://www.gnu.org/licenses/>.
16
17use crate::{CompilerState, ConditionalTreeNode, static_analysis::await_checker::AwaitChecker};
18
19use leo_ast::*;
20use leo_errors::{StaticAnalyzerError, StaticAnalyzerWarning};
21use leo_span::{Span, Symbol};
22
23pub struct StaticAnalyzingVisitor<'a> {
24    pub state: &'a mut CompilerState,
25    /// Struct to store the state relevant to checking all futures are awaited.
26    pub await_checker: AwaitChecker,
27    /// The current program name.
28    pub current_program: Symbol,
29    /// The variant of the function that we are currently traversing.
30    pub variant: Option<Variant>,
31    /// Whether or not a non-async external call has been seen in this function.
32    pub non_async_external_call_seen: bool,
33}
34
35impl StaticAnalyzingVisitor<'_> {
36    pub fn emit_err(&self, err: StaticAnalyzerError) {
37        self.state.handler.emit_err(err);
38    }
39
40    /// Emits a type checker warning
41    pub fn emit_warning(&self, warning: StaticAnalyzerWarning) {
42        self.state.handler.emit_warning(warning);
43    }
44
45    /// Type checks the awaiting of a future.
46    pub fn assert_future_await(&mut self, future: &Option<&Expression>, span: Span) {
47        // Make sure that it is an identifier expression.
48        let future_variable = match future {
49            Some(Expression::Path(path)) => path,
50            _ => {
51                return self.emit_err(StaticAnalyzerError::invalid_await_call(span));
52            }
53        };
54
55        // Make sure that the future is defined.
56        match self.state.type_table.get(&future_variable.id) {
57            Some(type_) => {
58                if !matches!(type_, Type::Future(_)) {
59                    self.emit_err(StaticAnalyzerError::expected_future(type_, future_variable.span()));
60                }
61                // Mark the future as consumed.
62                // If the call returns true, it means that a future was not awaited in the order of the input list, emit a warning.
63                if self.await_checker.remove(&future_variable.identifier().name) {
64                    self.emit_warning(StaticAnalyzerWarning::future_not_awaited_in_order(
65                        future_variable,
66                        future_variable.span(),
67                    ));
68                }
69            }
70            None => {
71                self.emit_err(StaticAnalyzerError::expected_future(future_variable, future_variable.span()));
72            }
73        }
74    }
75
76    /// Assert that an async call is a "simple" one.
77    /// Simple is defined as an async transition function which does not return a `Future` that itself takes a `Future` as an argument.
78    pub fn assert_simple_async_transition_call(&mut self, program: Symbol, function_path: &Path, span: Span) {
79        let func_symbol = self
80            .state
81            .symbol_table
82            .lookup_function(&Location::new(program, function_path.absolute_path().to_vec()))
83            .expect("Type checking guarantees functions are present.");
84
85        // If it is not an async transition, return.
86        if func_symbol.function.variant != Variant::AsyncTransition {
87            return;
88        }
89
90        let finalizer = func_symbol
91            .finalizer
92            .as_ref()
93            .expect("Typechecking guarantees that all async transitions have an associated `finalize` field.");
94
95        let async_function = self
96            .state
97            .symbol_table
98            .lookup_function(&finalizer.location)
99            .expect("Type checking guarantees functions are present.");
100
101        // If the async function takes a future as an argument, emit an error.
102        if async_function.function.input.iter().any(|input| matches!(input.type_(), Type::Future(..))) {
103            self.emit_err(StaticAnalyzerError::async_transition_call_with_future_argument(function_path, span));
104        }
105    }
106}
107
108impl AstVisitor for StaticAnalyzingVisitor<'_> {
109    /* Expressions */
110    type AdditionalInput = ();
111    type Output = ();
112
113    fn visit_intrinsic(&mut self, input: &IntrinsicExpression, _additional: &Self::AdditionalInput) -> Self::Output {
114        // Check `Future::await` core functions.
115        if let Some(Intrinsic::FutureAwait) = Intrinsic::from_symbol(input.name, &input.type_parameters) {
116            self.assert_future_await(&input.arguments.first(), input.span());
117        }
118    }
119
120    fn visit_call(&mut self, input: &CallExpression, _: &Self::AdditionalInput) -> Self::Output {
121        let caller_program = self.current_program;
122        let callee_program = input.program.unwrap_or(caller_program);
123
124        // If the function call is an external async transition, then for all async calls that follow a non-async call,
125        // we must check that the async call is not an async function that takes a future as an argument.
126        if self.non_async_external_call_seen
127            && self.variant == Some(Variant::AsyncTransition)
128            && callee_program != caller_program
129        {
130            self.assert_simple_async_transition_call(callee_program, &input.function, input.span());
131        }
132
133        // Look up the function and check if it is a non-async call.
134        let function_program = input.program.unwrap_or(self.current_program);
135
136        let func_symbol = self
137            .state
138            .symbol_table
139            .lookup_function(&Location::new(function_program, input.function.absolute_path().to_vec()))
140            .expect("Type checking guarantees functions exist.");
141
142        if func_symbol.function.variant == Variant::Transition {
143            self.non_async_external_call_seen = true;
144        }
145    }
146
147    /* Statements */
148    fn visit_conditional(&mut self, input: &ConditionalStatement) {
149        self.visit_expression(&input.condition, &Default::default());
150
151        // Create scope for checking awaits in `then` branch of conditional.
152        let current_bst_nodes: Vec<ConditionalTreeNode> =
153            match self.await_checker.create_then_scope(self.variant == Some(Variant::AsyncFunction), input.span) {
154                Ok(nodes) => nodes,
155                Err(warn) => return self.emit_warning(warn),
156            };
157
158        // Visit block.
159        self.visit_block(&input.then);
160
161        // Exit scope for checking awaits in `then` branch of conditional.
162        let saved_paths =
163            self.await_checker.exit_then_scope(self.variant == Some(Variant::AsyncFunction), current_bst_nodes);
164
165        if let Some(otherwise) = &input.otherwise {
166            match &**otherwise {
167                Statement::Block(stmt) => {
168                    // Visit the otherwise-block.
169                    self.visit_block(stmt);
170                }
171                Statement::Conditional(stmt) => self.visit_conditional(stmt),
172                _ => unreachable!("Else-case can only be a block or conditional statement."),
173            }
174        }
175
176        // Update the set of all possible BST paths.
177        self.await_checker.exit_statement_scope(self.variant == Some(Variant::AsyncFunction), saved_paths);
178    }
179}
leo_passes/static_analysis/visitor.rs

leo_passes/static_analysis/
visitor.rs
