Auto merge of rust-lang#6280 - dp304:assert_in_result_fn, r=ebroto

Add lint for assertions in functions returning Result

changelog: none
fixes rust-lang#6082

clippy_lints/src/panic_in_result_fn.rs

@@ -1,18 +1,16 @@
-use crate::utils::{is_expn_of, is_type_diagnostic_item, return_ty, span_lint_and_then};
+use crate::utils::{find_macro_calls, is_type_diagnostic_item, return_ty, span_lint_and_then};
 use rustc_hir as hir;
-use rustc_hir::intravisit::{self, FnKind, NestedVisitorMap, Visitor};
-use rustc_hir::Expr;
+use rustc_hir::intravisit::FnKind;
 use rustc_lint::{LateContext, LateLintPass};
-use rustc_middle::hir::map::Map;
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 use rustc_span::{sym, Span};
 
 declare_clippy_lint! {
-    /// **What it does:** Checks for usage of `panic!`, `unimplemented!`, `todo!` or `unreachable!` in a function of type result.
+    /// **What it does:** Checks for usage of `panic!`, `unimplemented!`, `todo!`, `unreachable!` or assertions in a function of type result.
     ///
-    /// **Why is this bad?** For some codebases, it is desirable for functions of type result to return an error instead of crashing. Hence unimplemented, panic and unreachable should be avoided.
+    /// **Why is this bad?** For some codebases, it is desirable for functions of type result to return an error instead of crashing. Hence panicking macros should be avoided.
     ///
-    /// **Known problems:** None.
+    /// **Known problems:** Functions called from a function returning a `Result` may invoke a panicking macro. This is not checked.
     ///
     /// **Example:**
     ///
@@ -22,9 +20,15 @@ declare_clippy_lint! {
     ///     panic!("error");
     /// }
     /// ```
+    /// Use instead:
+    /// ```rust
+    /// fn result_without_panic() -> Result<bool, String> {
+    ///     Err(String::from("error"))
+    /// }
+    /// ```
     pub PANIC_IN_RESULT_FN,
     restriction,
-    "functions of type `Result<..>` that contain `panic!()`, `todo!()` or `unreachable()` or `unimplemented()` "
+    "functions of type `Result<..>` that contain `panic!()`, `todo!()`, `unreachable()`, `unimplemented()` or assertion"
 }
 
 declare_lint_pass!(PanicInResultFn  => [PANIC_IN_RESULT_FN]);
@@ -47,43 +51,33 @@ impl<'tcx> LateLintPass<'tcx> for PanicInResultFn {
     }
 }
 
-struct FindPanicUnimplementedUnreachable {
-    result: Vec<Span>,
-}
-
-impl<'tcx> Visitor<'tcx> for FindPanicUnimplementedUnreachable {
-    type Map = Map<'tcx>;
-
-    fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
-        if ["unimplemented", "unreachable", "panic", "todo"]
-            .iter()
-            .any(|fun| is_expn_of(expr.span, fun).is_some())
-        {
-            self.result.push(expr.span);
-        }
-        // and check sub-expressions
-        intravisit::walk_expr(self, expr);
-    }
-
-    fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
-        NestedVisitorMap::None
-    }
-}
-
 fn lint_impl_body<'tcx>(cx: &LateContext<'tcx>, impl_span: Span, body: &'tcx hir::Body<'tcx>) {
-    let mut panics = FindPanicUnimplementedUnreachable { result: Vec::new() };
-    panics.visit_expr(&body.value);
-    if !panics.result.is_empty() {
+    let panics = find_macro_calls(
+        &[
+            "unimplemented",
+            "unreachable",
+            "panic",
+            "todo",
+            "assert",
+            "assert_eq",
+            "assert_ne",
+            "debug_assert",
+            "debug_assert_eq",
+            "debug_assert_ne",
+        ],
+        body,
+    );
+    if !panics.is_empty() {
         span_lint_and_then(
             cx,
             PANIC_IN_RESULT_FN,
             impl_span,
-            "used `unimplemented!()`, `unreachable!()`, `todo!()` or `panic!()` in a function that returns `Result`",
+            "used `unimplemented!()`, `unreachable!()`, `todo!()`, `panic!()` or assertion in a function that returns `Result`",
             move |diag| {
                 diag.help(
-                    "`unimplemented!()`, `unreachable!()`, `todo!()` or `panic!()` should not be used in a function that returns `Result` as `Result` is expected to return an error instead of crashing",
+                    "`unimplemented!()`, `unreachable!()`, `todo!()`, `panic!()` or assertions should not be used in a function that returns `Result` as `Result` is expected to return an error instead of crashing",
                 );
-                diag.span_note(panics.result, "return Err() instead of panicking");
+                diag.span_note(panics, "return Err() instead of panicking");
             },
         );
     }

clippy_lints/src/utils/mod.rs

@@ -41,7 +41,7 @@ use rustc_errors::Applicability;
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::{DefId, CRATE_DEF_INDEX, LOCAL_CRATE};
-use rustc_hir::intravisit::{NestedVisitorMap, Visitor};
+use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
 use rustc_hir::Node;
 use rustc_hir::{
     def, Arm, Block, Body, Constness, Crate, Expr, ExprKind, FnDecl, HirId, ImplItem, ImplItemKind, Item, ItemKind,
@@ -603,6 +603,37 @@ pub fn contains_return(expr: &hir::Expr<'_>) -> bool {
     visitor.found
 }
 
+struct FindMacroCalls<'a, 'b> {
+    names: &'a [&'b str],
+    result: Vec<Span>,
+}
+
+impl<'a, 'b, 'tcx> Visitor<'tcx> for FindMacroCalls<'a, 'b> {
+    type Map = Map<'tcx>;
+
+    fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
+        if self.names.iter().any(|fun| is_expn_of(expr.span, fun).is_some()) {
+            self.result.push(expr.span);
+        }
+        // and check sub-expressions
+        intravisit::walk_expr(self, expr);
+    }
+
+    fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
+        NestedVisitorMap::None
+    }
+}
+
+/// Finds calls of the specified macros in a function body.
+pub fn find_macro_calls(names: &[&str], body: &Body<'_>) -> Vec<Span> {
+    let mut fmc = FindMacroCalls {
+        names,
+        result: Vec::new(),
+    };
+    fmc.visit_expr(&body.value);
+    fmc.result
+}
+
 /// Converts a span to a code snippet if available, otherwise use default.
 ///
 /// This is useful if you want to provide suggestions for your lint or more generally, if you want

tests/ui/panic_in_result_fn.stderr

@@ -1,4 +1,4 @@
-error: used `unimplemented!()`, `unreachable!()`, `todo!()` or `panic!()` in a function that returns `Result`
+error: used `unimplemented!()`, `unreachable!()`, `todo!()`, `panic!()` or assertion in a function that returns `Result`
   --> $DIR/panic_in_result_fn.rs:7:5
    |
 LL | /     fn result_with_panic() -> Result<bool, String> // should emit lint
@@ -8,15 +8,15 @@ LL | |     }
    | |_____^
    |
    = note: `-D clippy::panic-in-result-fn` implied by `-D warnings`
-   = help: `unimplemented!()`, `unreachable!()`, `todo!()` or `panic!()` should not be used in a function that returns `Result` as `Result` is expected to return an error instead of crashing
+   = help: `unimplemented!()`, `unreachable!()`, `todo!()`, `panic!()` or assertions should not be used in a function that returns `Result` as `Result` is expected to return an error instead of crashing
 note: return Err() instead of panicking
   --> $DIR/panic_in_result_fn.rs:9:9
    |
 LL |         panic!("error");
    |         ^^^^^^^^^^^^^^^^
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: used `unimplemented!()`, `unreachable!()`, `todo!()` or `panic!()` in a function that returns `Result`
+error: used `unimplemented!()`, `unreachable!()`, `todo!()`, `panic!()` or assertion in a function that returns `Result`
   --> $DIR/panic_in_result_fn.rs:12:5
    |
 LL | /     fn result_with_unimplemented() -> Result<bool, String> // should emit lint
@@ -25,15 +25,15 @@ LL | |         unimplemented!();
 LL | |     }
    | |_____^
    |
-   = help: `unimplemented!()`, `unreachable!()`, `todo!()` or `panic!()` should not be used in a function that returns `Result` as `Result` is expected to return an error instead of crashing
+   = help: `unimplemented!()`, `unreachable!()`, `todo!()`, `panic!()` or assertions should not be used in a function that returns `Result` as `Result` is expected to return an error instead of crashing
 note: return Err() instead of panicking
   --> $DIR/panic_in_result_fn.rs:14:9
    |
 LL |         unimplemented!();
    |         ^^^^^^^^^^^^^^^^^
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: used `unimplemented!()`, `unreachable!()`, `todo!()` or `panic!()` in a function that returns `Result`
+error: used `unimplemented!()`, `unreachable!()`, `todo!()`, `panic!()` or assertion in a function that returns `Result`
   --> $DIR/panic_in_result_fn.rs:17:5
    |
 LL | /     fn result_with_unreachable() -> Result<bool, String> // should emit lint
@@ -42,15 +42,15 @@ LL | |         unreachable!();
 LL | |     }
    | |_____^
    |
-   = help: `unimplemented!()`, `unreachable!()`, `todo!()` or `panic!()` should not be used in a function that returns `Result` as `Result` is expected to return an error instead of crashing
+   = help: `unimplemented!()`, `unreachable!()`, `todo!()`, `panic!()` or assertions should not be used in a function that returns `Result` as `Result` is expected to return an error instead of crashing
 note: return Err() instead of panicking
   --> $DIR/panic_in_result_fn.rs:19:9
    |
 LL |         unreachable!();
    |         ^^^^^^^^^^^^^^^
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: used `unimplemented!()`, `unreachable!()`, `todo!()` or `panic!()` in a function that returns `Result`
+error: used `unimplemented!()`, `unreachable!()`, `todo!()`, `panic!()` or assertion in a function that returns `Result`
   --> $DIR/panic_in_result_fn.rs:22:5
    |
 LL | /     fn result_with_todo() -> Result<bool, String> // should emit lint
@@ -59,15 +59,15 @@ LL | |         todo!("Finish this");
 LL | |     }
    | |_____^
    |
-   = help: `unimplemented!()`, `unreachable!()`, `todo!()` or `panic!()` should not be used in a function that returns `Result` as `Result` is expected to return an error instead of crashing
+   = help: `unimplemented!()`, `unreachable!()`, `todo!()`, `panic!()` or assertions should not be used in a function that returns `Result` as `Result` is expected to return an error instead of crashing
 note: return Err() instead of panicking
   --> $DIR/panic_in_result_fn.rs:24:9
    |
 LL |         todo!("Finish this");
    |         ^^^^^^^^^^^^^^^^^^^^^
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: used `unimplemented!()`, `unreachable!()`, `todo!()` or `panic!()` in a function that returns `Result`
+error: used `unimplemented!()`, `unreachable!()`, `todo!()`, `panic!()` or assertion in a function that returns `Result`
   --> $DIR/panic_in_result_fn.rs:53:1
    |
 LL | / fn function_result_with_panic() -> Result<bool, String> // should emit lint
@@ -76,15 +76,15 @@ LL | |     panic!("error");
 LL | | }
    | |_^
    |
-   = help: `unimplemented!()`, `unreachable!()`, `todo!()` or `panic!()` should not be used in a function that returns `Result` as `Result` is expected to return an error instead of crashing
+   = help: `unimplemented!()`, `unreachable!()`, `todo!()`, `panic!()` or assertions should not be used in a function that returns `Result` as `Result` is expected to return an error instead of crashing
 note: return Err() instead of panicking
   --> $DIR/panic_in_result_fn.rs:55:5
    |
 LL |     panic!("error");
    |     ^^^^^^^^^^^^^^^^
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: used `unimplemented!()`, `unreachable!()`, `todo!()` or `panic!()` in a function that returns `Result`
+error: used `unimplemented!()`, `unreachable!()`, `todo!()`, `panic!()` or assertion in a function that returns `Result`
   --> $DIR/panic_in_result_fn.rs:68:1
    |
 LL | / fn main() -> Result<(), String> {
@@ -93,7 +93,7 @@ LL | |     Ok(())
 LL | | }
    | |_^
    |
-   = help: `unimplemented!()`, `unreachable!()`, `todo!()` or `panic!()` should not be used in a function that returns `Result` as `Result` is expected to return an error instead of crashing
+   = help: `unimplemented!()`, `unreachable!()`, `todo!()`, `panic!()` or assertions should not be used in a function that returns `Result` as `Result` is expected to return an error instead of crashing
 note: return Err() instead of panicking
   --> $DIR/panic_in_result_fn.rs:69:5
    |

tests/ui/panic_in_result_fn_assertions.rs

@@ -0,0 +1,48 @@
+#![warn(clippy::panic_in_result_fn)]
+#![allow(clippy::unnecessary_wraps)]
+
+struct A;
+
+impl A {
+    fn result_with_assert_with_message(x: i32) -> Result<bool, String> // should emit lint
+    {
+        assert!(x == 5, "wrong argument");
+        Ok(true)
+    }
+
+    fn result_with_assert_eq(x: i32) -> Result<bool, String> // should emit lint
+    {
+        assert_eq!(x, 5);
+        Ok(true)
+    }
+
+    fn result_with_assert_ne(x: i32) -> Result<bool, String> // should emit lint
+    {
+        assert_ne!(x, 1);
+        Ok(true)
+    }
+
+    fn other_with_assert_with_message(x: i32) // should not emit lint
+    {
+        assert!(x == 5, "wrong argument");
+    }
+
+    fn other_with_assert_eq(x: i32) // should not emit lint
+    {
+        assert_eq!(x, 5);
+    }
+
+    fn other_with_assert_ne(x: i32) // should not emit lint
+    {
+        assert_ne!(x, 1);
+    }
+
+    fn result_without_banned_functions() -> Result<bool, String> // should not emit lint
+    {
+        let assert = "assert!";
+        println!("No {}", assert);
+        Ok(true)
+    }
+}
+
+fn main() {}

tests/ui/panic_in_result_fn_assertions.stderr

@@ -0,0 +1,57 @@
+error: used `unimplemented!()`, `unreachable!()`, `todo!()`, `panic!()` or assertion in a function that returns `Result`
+  --> $DIR/panic_in_result_fn_assertions.rs:7:5
+   |
+LL | /     fn result_with_assert_with_message(x: i32) -> Result<bool, String> // should emit lint
+LL | |     {
+LL | |         assert!(x == 5, "wrong argument");
+LL | |         Ok(true)
+LL | |     }
+   | |_____^
+   |
+   = note: `-D clippy::panic-in-result-fn` implied by `-D warnings`
+   = help: `unimplemented!()`, `unreachable!()`, `todo!()`, `panic!()` or assertions should not be used in a function that returns `Result` as `Result` is expected to return an error instead of crashing
+note: return Err() instead of panicking
+  --> $DIR/panic_in_result_fn_assertions.rs:9:9
+   |
+LL |         assert!(x == 5, "wrong argument");
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: used `unimplemented!()`, `unreachable!()`, `todo!()`, `panic!()` or assertion in a function that returns `Result`
+  --> $DIR/panic_in_result_fn_assertions.rs:13:5
+   |
+LL | /     fn result_with_assert_eq(x: i32) -> Result<bool, String> // should emit lint
+LL | |     {
+LL | |         assert_eq!(x, 5);
+LL | |         Ok(true)
+LL | |     }
+   | |_____^
+   |
+   = help: `unimplemented!()`, `unreachable!()`, `todo!()`, `panic!()` or assertions should not be used in a function that returns `Result` as `Result` is expected to return an error instead of crashing
+note: return Err() instead of panicking
+  --> $DIR/panic_in_result_fn_assertions.rs:15:9
+   |
+LL |         assert_eq!(x, 5);
+   |         ^^^^^^^^^^^^^^^^^
+   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: used `unimplemented!()`, `unreachable!()`, `todo!()`, `panic!()` or assertion in a function that returns `Result`
+  --> $DIR/panic_in_result_fn_assertions.rs:19:5
+   |
+LL | /     fn result_with_assert_ne(x: i32) -> Result<bool, String> // should emit lint
+LL | |     {
+LL | |         assert_ne!(x, 1);
+LL | |         Ok(true)
+LL | |     }
+   | |_____^
+   |
+   = help: `unimplemented!()`, `unreachable!()`, `todo!()`, `panic!()` or assertions should not be used in a function that returns `Result` as `Result` is expected to return an error instead of crashing
+note: return Err() instead of panicking
+  --> $DIR/panic_in_result_fn_assertions.rs:21:9
+   |
+LL |         assert_ne!(x, 1);
+   |         ^^^^^^^^^^^^^^^^^
+   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to 3 previous errors
+