Merge pull request #241 from xFrednet/052-expressions-question-mark

API: Rename `QuestionMarkExpr` -> `TryExpr` (Breaking change)

Author: xFrednet

marker_api/src/ast/expr.rs

@@ -61,7 +61,7 @@ pub enum ExprKind<'ast> {
     UnaryOp(&'ast UnaryOpExpr<'ast>),
     Ref(&'ast RefExpr<'ast>),
     BinaryOp(&'ast BinaryOpExpr<'ast>),
-    QuestionMark(&'ast QuestionMarkExpr<'ast>),
+    Try(&'ast TryExpr<'ast>),
     Assign(&'ast AssignExpr<'ast>),
     As(&'ast AsExpr<'ast>),
     Path(&'ast PathExpr<'ast>),
@@ -180,7 +180,7 @@ pub enum ExprPrecedence {
     Fn = 0x1000_0000,
     Index = 0x1000_0001,
 
-    QuestionMark = 0x0F00_0000,
+    Try = 0x0F00_0000,
 
     /// The unary `-` operator
     Neg = 0x0E00_0000,
@@ -249,7 +249,7 @@ macro_rules! impl_expr_kind_fn {
         impl_expr_kind_fn!((ExprKind) $method() -> $return_ty,
             IntLit, FloatLit, StrLit, CharLit, BoolLit,
             Block, Closure,
-            UnaryOp, Ref, BinaryOp, QuestionMark, As, Assign,
+            UnaryOp, Ref, BinaryOp, Try, As, Assign,
             Path, Index, Field,
             Call, Method,
             Array, Tuple, Ctor, Range,
@@ -384,7 +384,7 @@ mod test {
         assert_eq!(40, size_of::<UnaryOpExpr<'_>>(), "UnaryOpExpr<'_>");
         assert_eq!(40, size_of::<RefExpr<'_>>(), "RefExpr<'_>");
         assert_eq!(56, size_of::<BinaryOpExpr<'_>>(), "BinaryOpExpr<'_>");
-        assert_eq!(32, size_of::<QuestionMarkExpr<'_>>(), "QuestionMarkExpr<'_>");
+        assert_eq!(32, size_of::<TryExpr<'_>>(), "TryExpr<'_>");
         assert_eq!(80, size_of::<AssignExpr<'_>>(), "AssignExpr<'_>");
         assert_eq!(48, size_of::<AsExpr<'_>>(), "AsExpr<'_>");
         assert_eq!(96, size_of::<PathExpr<'_>>(), "PathExpr<'_>");

marker_api/src/ast/expr/op_exprs.rs

@@ -142,23 +142,57 @@ impl<'ast> RefExpr<'ast> {
     }
 }
 
+/// The `?` operator that unwraps valid values or propagates erroneous values to
+/// the the calling function.
+///
+/// Here is an example of the operator:
+///
+/// ```
+/// fn try_option_example(opt: Option<i32>) -> Option<String> {
+///     // The `?` operator unwraps the value if `opt` is `Some` or
+///     // propagates `None` if `opt` is empty.
+///     //             v
+///     let value = opt?;
+///     // `value` has the type `i32`
+///     
+///     // [...]
+///     # Some(value.to_string())
+/// }
+///
+/// fn try_result_example(res: Result<i32, ()>) -> Result<String, ()> {
+///     // The `?` operator unwraps the value if `res` is `Ok` or
+///     // propagates the value of `Err` if `res` is an error.
+///     //             v
+///     let value = res?;
+///     // `value` has the type `i32`
+///     
+///     // [...]
+///     # Ok(value.to_string())
+/// }
+/// ```
+///
+/// This operator is also known as the *question mark* or *error propagation* operator.
+///
+/// See <https://doc.rust-lang.org/reference/expressions/operator-expr.html#the-question-mark-operator>
 #[repr(C)]
 #[derive(Debug)]
-pub struct QuestionMarkExpr<'ast> {
+pub struct TryExpr<'ast> {
     data: CommonExprData<'ast>,
     expr: ExprKind<'ast>,
 }
 
-impl<'ast> QuestionMarkExpr<'ast> {
+impl<'ast> TryExpr<'ast> {
+    /// The expression that might produce an error, that would be propagated by
+    /// this operator.
     pub fn expr(&self) -> ExprKind<'ast> {
         self.expr
     }
 }
 
-super::impl_expr_data!(QuestionMarkExpr<'ast>, QuestionMark);
+super::impl_expr_data!(TryExpr<'ast>, Try);
 
 #[cfg(feature = "driver-api")]
-impl<'ast> QuestionMarkExpr<'ast> {
+impl<'ast> TryExpr<'ast> {
     pub fn new(data: CommonExprData<'ast>, expr: ExprKind<'ast>) -> Self {
         Self { data, expr }
     }

marker_rustc_driver/src/conversion/marker/expr.rs

@@ -4,9 +4,9 @@ use marker_api::{
             ArrayExpr, AsExpr, AssignExpr, AwaitExpr, BinaryOpExpr, BinaryOpKind, BlockExpr, BoolLitExpr, BreakExpr,
             CallExpr, CaptureKind, CharLitExpr, ClosureExpr, ClosureParam, CommonExprData, ConstExpr, ContinueExpr,
             CtorExpr, CtorField, ExprKind, ExprPrecedence, FieldExpr, FloatLitExpr, FloatSuffix, ForExpr, IfExpr,
-            IndexExpr, IntLitExpr, IntSuffix, LetExpr, LoopExpr, MatchArm, MatchExpr, MethodExpr, PathExpr,
-            QuestionMarkExpr, RangeExpr, RefExpr, ReturnExpr, StrLitData, StrLitExpr, TupleExpr, UnaryOpExpr,
-            UnaryOpKind, UnstableExpr, WhileExpr,
+            IndexExpr, IntLitExpr, IntSuffix, LetExpr, LoopExpr, MatchArm, MatchExpr, MethodExpr, PathExpr, RangeExpr,
+            RefExpr, ReturnExpr, StrLitData, StrLitExpr, TryExpr, TupleExpr, UnaryOpExpr, UnaryOpKind, UnstableExpr,
+            WhileExpr,
         },
         pat::PatKind,
         Ident, Safety, Syncness,
@@ -210,7 +210,7 @@ impl<'ast, 'tcx> MarkerConverterInner<'ast, 'tcx> {
                 ExprKind::Match(self.alloc(MatchExpr::new(data, self.to_expr(scrutinee), self.to_match_arms(arms))))
             },
             hir::ExprKind::Match(_scrutinee, [_early_return, _continue], hir::MatchSource::TryDesugar(_)) => {
-                ExprKind::QuestionMark(self.alloc(self.to_try_expr_from_desugar(expr)))
+                ExprKind::Try(self.alloc(self.to_try_expr_from_desugar(expr)))
             },
             hir::ExprKind::Match(_scrutinee, [_awaitee_arm], hir::MatchSource::AwaitDesugar) => {
                 ExprKind::Await(self.alloc(self.to_await_expr_from_desugar(expr)))
@@ -552,10 +552,10 @@ impl<'ast, 'tcx> MarkerConverterInner<'ast, 'tcx> {
         }
     }
 
-    fn to_try_expr_from_desugar(&self, try_desugar: &hir::Expr<'tcx>) -> QuestionMarkExpr<'ast> {
+    fn to_try_expr_from_desugar(&self, try_desugar: &hir::Expr<'tcx>) -> TryExpr<'ast> {
         if let hir::ExprKind::Match(scrutinee, [_ret, _con], hir::MatchSource::TryDesugar(_)) = try_desugar.kind {
             if let hir::ExprKind::Call(_try_path, [tested_expr]) = scrutinee.kind {
-                return QuestionMarkExpr::new(
+                return TryExpr::new(
                     CommonExprData::new(self.to_expr_id(try_desugar.hir_id), self.to_span_id(try_desugar.span)),
                     self.to_expr(tested_expr),
                 );

marker_uilints/tests/ui/print_cond_expr.stderr

@@ -1018,8 +1018,8 @@ warning: print test
 48 |         let _print_option_match = x?;
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = note: QuestionMark(
-               QuestionMarkExpr {
+   = note: Try(
+               TryExpr {
                    data: CommonExprData {
                        _lifetime: PhantomData<&()>,
                        id: ExprId(..),
@@ -1063,8 +1063,8 @@ warning: print test
 54 |         let _print_result_match = x?;
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = note: QuestionMark(
-               QuestionMarkExpr {
+   = note: Try(
+               TryExpr {
                    data: CommonExprData {
                        _lifetime: PhantomData<&()>,
                        id: ExprId(..),

marker_utils/src/visitor.rs

@@ -248,7 +248,7 @@ pub fn traverse_expr<'ast, B>(
             traverse_expr(cx, visitor, e.left())?;
             traverse_expr(cx, visitor, e.right())?;
         },
-        ExprKind::QuestionMark(e) => {
+        ExprKind::Try(e) => {
             traverse_expr(cx, visitor, e.expr())?;
         },
         ExprKind::Assign(e) => {
@@ -448,14 +448,14 @@ impl_traversable_for!(&'ast Body<'ast>, traverse_body);
 pub trait BoolTraversable<'ast>: Traversable<'ast, bool> {
     /// Checks if the given node contains an early return, in the form of an
     /// [`ReturnExpr`](marker_api::ast::expr::ReturnExpr) or
-    /// [`QuestionMarkExpr`](marker_api::ast::expr::QuestionMarkExpr).
+    /// [`TryExpr`](marker_api::ast::expr::TryExpr).
     ///
     /// This function is useful, for lints which suggest moving code snippets into
     /// a closure or different function. Return statements might prevent the suggested
     /// refactoring.
     fn contains_return(&self, cx: &'ast AstContext<'ast>) -> bool {
         self.for_each_expr(cx, |expr| {
-            if matches!(expr, ExprKind::Return(_) | ExprKind::QuestionMark(_)) {
+            if matches!(expr, ExprKind::Return(_) | ExprKind::Try(_)) {
                 ControlFlow::Break(true)
             } else {
                 ControlFlow::Continue(())