[move][move-linter] implement unnecessary while loop rules

external-crates/move/crates/move-compiler/src/linters/unnecessary_while_loop.rs

@@ -0,0 +1,78 @@
+//! Encourages replacing `while(true)` with `loop` for infinite loops in Move for clarity and conciseness.
+//! Identifies `while(true)` patterns, suggesting a more idiomatic approach using `loop`.
+//! Aims to enhance code readability and adherence to Rust idioms.
+use crate::{
+    diag,
+    diagnostics::{
+        codes::{custom, DiagnosticInfo, Severity},
+        WarningFilters,
+    },
+    expansion::ast::Value_,
+    shared::CompilationEnv,
+    typing::{
+        ast::{self as T, UnannotatedExp_},
+        visitor::{TypingVisitorConstructor, TypingVisitorContext},
+    },
+};
+use move_ir_types::location::Loc;
+
+use super::{LinterDiagnosticCategory, LINT_WARNING_PREFIX, WHILE_TRUE_TO_LOOP_DIAG_CODE};
+
+const WHILE_TRUE_TO_LOOP_DIAG: DiagnosticInfo = custom(
+    LINT_WARNING_PREFIX,
+    Severity::Warning,
+    LinterDiagnosticCategory::Complexity as u8,
+    WHILE_TRUE_TO_LOOP_DIAG_CODE,
+    "",
+);
+
+pub struct WhileTrueToLoop;
+
+pub struct Context<'a> {
+    env: &'a mut CompilationEnv,
+}
+
+impl TypingVisitorConstructor for WhileTrueToLoop {
+    type Context<'a> = Context<'a>;
+
+    fn context<'a>(env: &'a mut CompilationEnv, _program: &T::Program) -> Self::Context<'a> {
+        Context { env }
+    }
+}
+
+impl TypingVisitorContext for Context<'_> {
+    fn visit_exp_custom(&mut self, exp: &mut T::Exp) -> bool {
+        if let UnannotatedExp_::While(_, cond, _) = &exp.exp.value {
+            if is_condition_always_true(&cond.exp.value) {
+                report_while_true_to_loop(self.env, exp.exp.loc);
+            }
+        }
+        false
+    }
+    fn add_warning_filter_scope(&mut self, filter: WarningFilters) {
+        self.env.add_warning_filter_scope(filter)
+    }
+
+    fn pop_warning_filter_scope(&mut self) {
+        self.env.pop_warning_filter_scope()
+    }
+}
+
+fn is_condition_always_true(condition: &UnannotatedExp_) -> bool {
+    if let UnannotatedExp_::Value(val) = condition {
+        if let Value_::Bool(b) = &val.value {
+            return *b;
+        }
+    }
+    false
+}
+fn report_while_true_to_loop(env: &mut CompilationEnv, loc: Loc) {
+    let diag = diag!(
+        WHILE_TRUE_TO_LOOP_DIAG,
+        (
+            loc,
+            "Detected `while(true) {}` loop. Consider replacing with `loop {}`"
+        )
+    );
+    env.add_diag(diag);
+}

external-crates/move/crates/move-compiler/tests/linter/correct_unnecessary_while_loop.move

@@ -0,0 +1,12 @@
+module 0x42::M {
+
+    public fun finite_loop() {
+        let counter = 0;
+        loop {
+            if(counter == 10) {
+                break
+            };
+            counter = counter + 1;
+        }
+    }
+}

external-crates/move/crates/move-compiler/tests/linter/incorrect_unnecessary_while_loop.exp

@@ -0,0 +1,13 @@
+warning[Lint W01013]: 
+   ┌─ tests/linter/incorrect_unnecessary_while_loop.move:5:9
+   │  
+ 5 │ ╭         while (true) {
+ 6 │ │             if(counter == 10) {
+ 7 │ │                 break
+ 8 │ │             };
+ 9 │ │             counter = counter + 1;
+10 │ │         }
+   │ ╰─────────^ Detected `while(true) {}` loop. Consider replacing with `loop {}`
+   │  
+   = This warning can be suppressed with '#[allow(lint(unnecessary_while_loop))]' applied to the 'module' or module member ('const', 'fun', or 'struct')
+

external-crates/move/crates/move-compiler/tests/linter/incorrect_unnecessary_while_loop.move

@@ -0,0 +1,12 @@
+module 0x42::M {
+
+    public fun finite_loop() {
+        let counter = 0;
+        while (true) {
+            if(counter == 10) {
+                break
+            };
+            counter = counter + 1;
+        }
+    }
+}

external-crates/move/crates/move-compiler/tests/linter/suppressed_lints.move

@@ -2,4 +2,15 @@ module 0x42::M {
 
     #[allow(lint(constant_naming))]
     const Another_BadName: u64 = 42; // Should trigger a warning
+
+    #[allow(lint(unnecessary_while_loop))]
+    public fun finite_loop() {
+        let counter = 0;
+        while (true) {
+            if(counter == 10) {
+                break
+            };
+            counter = counter + 1;
+        }
+    }
 }