Auto merge of rust-lang#124987 - workingjubilee:macro-metavar-expr-with-a-shorter-len, r=c410-f3r,joshtriplett,joshtriplett

Rename `${length()}` to `${len()}`

Implements the rename suggested in rust-lang#122808 (comment)
> I brought this up in the doc PR but it belongs here – `length` should probably be renamed `len` before stabilization. The latter is de facto standard in the standard library, whereas the former is only used in a single unstable API. These metafunctions aren’t library items of course, but should presumably still be consistent with established names.

r? `@c410-f3r`

Author: bors

compiler/rustc_expand/src/mbe/metavar_expr.rs

@@ -23,7 +23,7 @@ pub(crate) enum MetaVarExpr {
 
     /// The length of the repetition at a particular depth, where 0 is the inner-most
     /// repetition. The `usize` is the depth.
-    Length(usize),
+    Len(usize),
 }
 
 impl MetaVarExpr {
@@ -48,13 +48,13 @@ impl MetaVarExpr {
                 MetaVarExpr::Ignore(parse_ident(&mut iter, psess, ident.span)?)
             }
             "index" => MetaVarExpr::Index(parse_depth(&mut iter, psess, ident.span)?),
-            "length" => MetaVarExpr::Length(parse_depth(&mut iter, psess, ident.span)?),
+            "len" => MetaVarExpr::Len(parse_depth(&mut iter, psess, ident.span)?),
             _ => {
                 let err_msg = "unrecognized meta-variable expression";
                 let mut err = psess.dcx.struct_span_err(ident.span, err_msg);
                 err.span_suggestion(
                     ident.span,
-                    "supported expressions are count, ignore, index and length",
+                    "supported expressions are count, ignore, index and len",
                     "",
                     Applicability::MachineApplicable,
                 );
@@ -68,7 +68,7 @@ impl MetaVarExpr {
     pub(crate) fn ident(&self) -> Option<Ident> {
         match *self {
             MetaVarExpr::Count(ident, _) | MetaVarExpr::Ignore(ident) => Some(ident),
-            MetaVarExpr::Index(..) | MetaVarExpr::Length(..) => None,
+            MetaVarExpr::Index(..) | MetaVarExpr::Len(..) => None,
         }
     }
 }
@@ -111,7 +111,7 @@ fn parse_count<'psess>(
     Ok(MetaVarExpr::Count(ident, depth))
 }
 
-/// Parses the depth used by index(depth) and length(depth).
+/// Parses the depth used by index(depth) and len(depth).
 fn parse_depth<'psess>(
     iter: &mut RefTokenTreeCursor<'_>,
     psess: &'psess ParseSess,

compiler/rustc_expand/src/mbe/quoted.rs

@@ -357,7 +357,7 @@ fn parse_sep_and_kleene_op<'a>(
 
 // `$$` or a meta-variable is the lhs of a macro but shouldn't.
 //
-// For example, `macro_rules! foo { ( ${length()} ) => {} }`
+// For example, `macro_rules! foo { ( ${len()} ) => {} }`
 fn span_dollar_dollar_or_metavar_in_the_lhs_err(sess: &Session, token: &Token) {
     sess.dcx()
         .span_err(token.span, format!("unexpected token: {}", pprust::token_to_string(token)));

compiler/rustc_expand/src/mbe/transcribe.rs

@@ -685,14 +685,14 @@ fn transcribe_metavar_expr<'a>(
             }
             None => return Err(out_of_bounds_err(cx, repeats.len(), sp.entire(), "index")),
         },
-        MetaVarExpr::Length(depth) => match repeats.iter().nth_back(depth) {
+        MetaVarExpr::Len(depth) => match repeats.iter().nth_back(depth) {
             Some((_, length)) => {
                 result.push(TokenTree::token_alone(
                     TokenKind::lit(token::Integer, sym::integer(*length), None),
                     visited_span(),
                 ));
             }
-            None => return Err(out_of_bounds_err(cx, repeats.len(), sp.entire(), "length")),
+            None => return Err(out_of_bounds_err(cx, repeats.len(), sp.entire(), "len")),
         },
     }
     Ok(())

tests/ui/macros/meta-variable-depth-outside-repeat.rs

@@ -2,8 +2,8 @@
 
 macro_rules! metavar {
     ( $i:expr ) => {
-        ${length(0)}
-        //~^ ERROR meta-variable expression `length` with depth parameter must be called inside of a macro repetition
+        ${len(0)}
+        //~^ ERROR meta-variable expression `len` with depth parameter must be called inside of a macro repetition
     };
 }
 

tests/ui/macros/meta-variable-depth-outside-repeat.stderr

@@ -1,8 +1,8 @@
-error: meta-variable expression `length` with depth parameter must be called inside of a macro repetition
+error: meta-variable expression `len` with depth parameter must be called inside of a macro repetition
   --> $DIR/meta-variable-depth-outside-repeat.rs:5:10
    |
-LL |         ${length(0)}
-   |          ^^^^^^^^^^^
+LL |         ${len(0)}
+   |          ^^^^^^^^
 
 error: aborting due to 1 previous error
 

tests/ui/macros/rfc-3086-metavar-expr/count-and-length-are-distinct.rs

@@ -3,60 +3,55 @@
 #![feature(macro_metavar_expr)]
 
 fn main() {
-    macro_rules! one_nested_count_and_length {
+    macro_rules! one_nested_count_and_len {
         ( $( [ $( $l:literal ),* ] ),* ) => {
             [
                 // outer-most repetition
                 $(
                     // inner-most repetition
                     $(
-                        ${ignore($l)} ${index()}, ${length()},
+                        ${ignore($l)} ${index()}, ${len()},
                     )*
-                    ${count($l)}, ${index()}, ${length()},
+                    ${count($l)}, ${index()}, ${len()},
                 )*
                 ${count($l)},
             ]
         };
     }
     assert_eq!(
-        one_nested_count_and_length!(["foo"], ["bar", "baz"]),
+        one_nested_count_and_len!(["foo"], ["bar", "baz"]),
         [
             // # ["foo"]
 
             // ## inner-most repetition (first iteration)
             //
             // `index` is 0 because this is the first inner-most iteration.
-            // `length` is 1 because there is only one inner-most repetition, "foo".
+            // `len` is 1 because there is only one inner-most repetition, "foo".
             0, 1,
-
             // ## outer-most repetition (first iteration)
             //
             // `count` is 1 because of "foo", i,e, `$l` has only one repetition,
             // `index` is 0 because this is the first outer-most iteration.
-            // `length` is 2 because there are 2 outer-most repetitions, ["foo"] and ["bar", "baz"]
+            // `len` is 2 because there are 2 outer-most repetitions, ["foo"] and ["bar", "baz"]
             1, 0, 2,
-
             // # ["bar", "baz"]
 
             // ## inner-most repetition (first iteration)
             //
             // `index` is 0 because this is the first inner-most iteration
-            // `length` is 2 because there are repetitions, "bar" and "baz"
+            // `len` is 2 because there are repetitions, "bar" and "baz"
             0, 2,
-
             // ## inner-most repetition (second iteration)
             //
             // `index` is 1 because this is the second inner-most iteration
-            // `length` is 2 because there are repetitions, "bar" and "baz"
+            // `len` is 2 because there are repetitions, "bar" and "baz"
             1, 2,
-
             // ## outer-most repetition (second iteration)
             //
             // `count` is 2 because of "bar" and "baz", i,e, `$l` has two repetitions,
             // `index` is 1 because this is the second outer-most iteration
-            // `length` is 2 because there are 2 outer-most repetitions, ["foo"] and ["bar", "baz"]
+            // `len` is 2 because there are 2 outer-most repetitions, ["foo"] and ["bar", "baz"]
             2, 1, 2,
-
             // # last count
 
             // Because there are a total of 3 repetitions of `$l`, "foo", "bar" and "baz"
@@ -131,7 +126,6 @@ fn main() {
             &[2][..],
             // t u v w x y z
             &[7][..],
-
             // (a b c) (d e f)
             &[6, 2][..],
             // (g h) (i j k l m)
@@ -142,15 +136,13 @@ fn main() {
             &[5, 3][..],
             // (t u v w x y z)
             &[7, 1][..],
-
             // [ (a b c) (d e f) ]
             // [ (g h) (i j k l m) ]
             // [ (n) ]
             &[14, 5, 3][..],
             // [ (o) (p q) (r s) ]
             // [ (t u v w x y z) ]
             &[12, 4, 2][..],
-
             // {
             //     [ (a b c) (d e f) ]
             //     [ (g h) (i j k l m) ]
@@ -165,43 +157,43 @@ fn main() {
     );
 
     // Grouped from the outer-most to the inner-most
-    macro_rules! three_nested_length {
+    macro_rules! three_nested_len {
         ( $( { $( [ $( ( $( $i:ident )* ) )* ] )* } )* ) => {
             &[
                 $( $( $( $(
                     &[
-                        ${ignore($i)} ${length(3)},
-                        ${ignore($i)} ${length(2)},
-                        ${ignore($i)} ${length(1)},
-                        ${ignore($i)} ${length(0)},
+                        ${ignore($i)} ${len(3)},
+                        ${ignore($i)} ${len(2)},
+                        ${ignore($i)} ${len(1)},
+                        ${ignore($i)} ${len(0)},
                     ][..],
                 )* )* )* )*
 
                 $( $( $(
                     &[
-                        ${ignore($i)} ${length(2)},
-                        ${ignore($i)} ${length(1)},
-                        ${ignore($i)} ${length(0)},
+                        ${ignore($i)} ${len(2)},
+                        ${ignore($i)} ${len(1)},
+                        ${ignore($i)} ${len(0)},
                     ][..],
                 )* )* )*
 
                 $( $(
                     &[
-                        ${ignore($i)} ${length(1)},
-                        ${ignore($i)} ${length(0)},
+                        ${ignore($i)} ${len(1)},
+                        ${ignore($i)} ${len(0)},
                     ][..],
                 )* )*
 
                 $(
                     &[
-                        ${ignore($i)} ${length(0)},
+                        ${ignore($i)} ${len(0)},
                     ][..],
                 )*
             ][..]
         }
     }
     assert_eq!(
-        three_nested_length!(
+        three_nested_len!(
             {
                 [ (a b c) (d e f) ]
                 [ (g h) (i j k l m) ]
@@ -214,45 +206,64 @@ fn main() {
         ),
         &[
             // a b c
-            &[2, 3, 2, 3][..], &[2, 3, 2, 3][..], &[2, 3, 2, 3][..],
+            &[2, 3, 2, 3][..],
+            &[2, 3, 2, 3][..],
+            &[2, 3, 2, 3][..],
             // d e f
-            &[2, 3, 2, 3][..], &[2, 3, 2, 3][..], &[2, 3, 2, 3][..],
+            &[2, 3, 2, 3][..],
+            &[2, 3, 2, 3][..],
+            &[2, 3, 2, 3][..],
             // g h
-            &[2, 3, 2, 2][..], &[2, 3, 2, 2][..],
+            &[2, 3, 2, 2][..],
+            &[2, 3, 2, 2][..],
             // i j k l m
-            &[2, 3, 2, 5][..], &[2, 3, 2, 5][..], &[2, 3, 2, 5][..], &[2, 3, 2, 5][..],
+            &[2, 3, 2, 5][..],
+            &[2, 3, 2, 5][..],
+            &[2, 3, 2, 5][..],
+            &[2, 3, 2, 5][..],
             &[2, 3, 2, 5][..],
             // n
             &[2, 3, 1, 1][..],
             // o
             &[2, 2, 3, 1][..],
             // p q
-            &[2, 2, 3, 2][..], &[2, 2, 3, 2][..],
+            &[2, 2, 3, 2][..],
+            &[2, 2, 3, 2][..],
             // r s
-            &[2, 2, 3, 2][..], &[2, 2, 3, 2][..],
+            &[2, 2, 3, 2][..],
+            &[2, 2, 3, 2][..],
             // t u v w x y z
-            &[2, 2, 1, 7][..], &[2, 2, 1, 7][..], &[2, 2, 1, 7][..], &[2, 2, 1, 7][..],
-            &[2, 2, 1, 7][..], &[2, 2, 1, 7][..], &[2, 2, 1, 7][..],
-
+            &[2, 2, 1, 7][..],
+            &[2, 2, 1, 7][..],
+            &[2, 2, 1, 7][..],
+            &[2, 2, 1, 7][..],
+            &[2, 2, 1, 7][..],
+            &[2, 2, 1, 7][..],
+            &[2, 2, 1, 7][..],
             // (a b c) (d e f)
-            &[2, 3, 2][..], &[2, 3, 2][..],
+            &[2, 3, 2][..],
+            &[2, 3, 2][..],
             // (g h) (i j k l m)
-            &[2, 3, 2][..], &[2, 3, 2][..],
+            &[2, 3, 2][..],
+            &[2, 3, 2][..],
             // (n)
             &[2, 3, 1][..],
             // (o) (p q) (r s)
-            &[2, 2, 3][..], &[2, 2, 3][..], &[2, 2, 3][..],
+            &[2, 2, 3][..],
+            &[2, 2, 3][..],
+            &[2, 2, 3][..],
             // (t u v w x y z)
             &[2, 2, 1][..],
-
             // [ (a b c) (d e f) ]
             // [ (g h) (i j k l m) ]
             // [ (n) ]
-            &[2, 3][..], &[2, 3][..],  &[2, 3,][..],
+            &[2, 3][..],
+            &[2, 3][..],
+            &[2, 3,][..],
             // [ (o) (p q) (r s) ]
             // [ (t u v w x y z) ]
-            &[2, 2][..], &[2, 2][..],
-
+            &[2, 2][..],
+            &[2, 2][..],
             // {
             //     [ (a b c) (d e f) ]
             //     [ (g h) (i j k l m) ]
@@ -262,10 +273,11 @@ fn main() {
             //     [ (o) (p q) (r s) ]
             //     [ (t u v w x y z) ]
             // }
-            &[2][..], &[2][..]
+            &[2][..],
+            &[2][..]
         ][..]
     );
 
-    // It is possible to say, to some degree, that count is an "amalgamation" of length (see
-    // each length line result and compare them with the count results)
+    // It is possible to say, to some degree, that count is an "amalgamation" of len (see
+    // each len line result and compare them with the count results)
 }

tests/ui/macros/rfc-3086-metavar-expr/feature-gate-macro_metavar_expr.rs

@@ -37,17 +37,17 @@ macro_rules! count_depth_limits {
     };
 }
 
-/// Produce (index, length) pairs for literals in a macro repetition.
+/// Produce (index, len) pairs for literals in a macro repetition.
 /// The literal is not included in the output, so this macro uses the
 /// `ignore` meta-variable expression to create a non-expanding
 /// repetition binding.
 macro_rules! enumerate_literals {
     ( $( ($l:stmt) ),* ) => {
-        [$( ${ignore($l)} (${index()}, ${length()}) ),*]
+        [$( ${ignore($l)} (${index()}, ${len()}) ),*]
     };
 }
 
-/// Produce index and length tuples for literals in a 2-dimensional
+/// Produce index and len tuples for literals in a 2-dimensional
 /// macro repetition.
 macro_rules! enumerate_literals_2 {
     ( $( [ $( ($l:literal) ),* ] ),* ) => {
@@ -56,9 +56,9 @@ macro_rules! enumerate_literals_2 {
                 $(
                     (
                         ${index(1)},
-                        ${length(1)},
+                        ${len(1)},
                         ${index(0)},
-                        ${length(0)},
+                        ${len(0)},
                         $l
                     ),
                 )*
@@ -134,7 +134,6 @@ fn main() {
             (0, 2, 0, 3, "foo"),
             (0, 2, 1, 3, "bar"),
             (0, 2, 2, 3, "baz"),
-
             (1, 2, 0, 4, "qux"),
             (1, 2, 1, 4, "quux"),
             (1, 2, 2, 4, "quuz"),