Rename question mark operator

This renames the "question mark operator" section to the "try
propagation expression", and also drops the grammar name "error
propagation expression".

The "error propagation expression" isn't really accurate, since `?`
isn't just for errors.

The intent is to describe the expression by what it does (as most other
expressions do) instead of how it looks. It also felt a little awkward
to call it the "question mark expression".

Author: ehuss

src/expressions/operator-expr.md

@@ -6,7 +6,7 @@ r[expr.operator.syntax]
 OperatorExpression ->
       BorrowExpression
     | DereferenceExpression
-    | ErrorPropagationExpression
+    | TryPropagationExpression
     | NegationExpression
     | ArithmeticOrLogicalExpression
     | ComparisonExpression
@@ -190,15 +190,18 @@ assert_eq!(*y, 11);
 ```
 
 r[expr.try]
-## The question mark operator
+## The try propagation expression
 
 r[expr.try.syntax]
 ```grammar,expressions
-ErrorPropagationExpression -> Expression `?`
+TryPropagationExpression -> Expression `?`
 ```
 
 r[expr.try.intro]
-The question mark operator (`?`) unwraps valid values or returns erroneous values, propagating them to the calling function.
+The try propagation operator (`?`) unwraps valid values or returns erroneous values, propagating them to the calling function.
+
+> [!NOTE]
+> The try propagation operator is sometimes called *the question mark operator*, *the `?` operator*, or *the try operator*.
 
 r[expr.try.restricted-types]
 It is a unary postfix operator that can only be applied to the types `Result<T, E>` and `Option<T>`.
@@ -913,6 +916,7 @@ Like assignment expressions, compound assignment expressions always produce [the
 (function() {
     var fragments = {
         "#slice-dst-pointer-to-pointer-cast": "operator-expr.html#pointer-to-pointer-cast",
+        "#the-question-mark-operator": "operator-expr.html#the-try-propagation-expression",
     };
     var target = fragments[window.location.hash];
     if (target) {

src/tokens.md

@@ -907,7 +907,7 @@ usages and meanings are defined in the linked pages.
 | `<-`   | LArrow      | The left arrow symbol has been unused since before Rust 1.0, but it is still treated as a single token
 | `#`    | Pound       | [Attributes]
 | `$`    | Dollar      | [Macros]
-| `?`    | Question    | [Question mark operator][question], [Questionably sized][sized], [Macro Kleene Matcher][macros]
+| `?`    | Question    | [Try propagation expressions][question], [Questionably sized][sized], [Macro Kleene Matcher][macros]
 | `~`    | Tilde       | The tilde operator has been unused since before Rust 1.0, but its token may still be used
 
 r[lex.token.delim]
@@ -1064,7 +1064,7 @@ r[lex.token.reserved-guards.edition2024]
 [paths]: paths.md
 [patterns]: patterns.md
 [placeholder lifetime]: lifetime-elision.md
-[question]: expressions/operator-expr.md#the-question-mark-operator
+[question]: expressions/operator-expr.md#the-try-propagation-expression
 [range]: expressions/range-expr.md
 [rangepat]: patterns.md#range-patterns
 [raw pointers]: types/pointer.md#raw-pointers-const-and-mut