Remove parse error on array initializer attributes

This is actually allowed by the `rustc` parser but most attributes will
fail later due to attributes on expressions being experimental.

crates/ra_parser/src/grammar/expressions/atom.rs

@@ -177,21 +177,10 @@ fn array_expr(p: &mut Parser) -> CompletedMarker {
     //    1,
     //    2,
     // ];
-    let first_member_has_attrs = p.at(T![#]);
     attributes::outer_attributes(p);
 
     expr(p);
     if p.eat(T![;]) {
-        if first_member_has_attrs {
-            // test_err array_length_attributes
-            // pub const A: &[i64] = &[
-            //   #[cfg(test)]
-            //   1;
-            //   2,
-            // ];
-            p.error("removing an expression is not supported in this position");
-        }
-
         expr(p);
         p.expect(T![']']);
         return m.complete(p, ARRAY_EXPR);

crates/ra_syntax/tests/data/parser/inline/err/0015_array_length_attributes.rs

@@ -1,5 +0,0 @@
-pub const A: &[i64] = &[
-  #[cfg(test)]
-  1;
-  2,
-];

crates/ra_syntax/tests/data/parser/inline/err/0015_array_length_attributes.txt

@@ -1,60 +0,0 @@
-SOURCE_FILE@[0; 53)
-  CONST_DEF@[0; 48)
-    VISIBILITY@[0; 3)
-      PUB_KW@[0; 3) "pub"
-    WHITESPACE@[3; 4) " "
-    CONST_KW@[4; 9) "const"
-    WHITESPACE@[9; 10) " "
-    NAME@[10; 11)
-      IDENT@[10; 11) "A"
-    COLON@[11; 12) ":"
-    WHITESPACE@[12; 13) " "
-    REFERENCE_TYPE@[13; 19)
-      AMP@[13; 14) "&"
-      SLICE_TYPE@[14; 19)
-        L_BRACK@[14; 15) "["
-        PATH_TYPE@[15; 18)
-          PATH@[15; 18)
-            PATH_SEGMENT@[15; 18)
-              NAME_REF@[15; 18)
-                IDENT@[15; 18) "i64"
-        R_BRACK@[18; 19) "]"
-    WHITESPACE@[19; 20) " "
-    EQ@[20; 21) "="
-    WHITESPACE@[21; 22) " "
-    REF_EXPR@[22; 48)
-      AMP@[22; 23) "&"
-      ARRAY_EXPR@[23; 48)
-        L_BRACK@[23; 24) "["
-        WHITESPACE@[24; 27) "\n  "
-        ATTR@[27; 39)
-          POUND@[27; 28) "#"
-          TOKEN_TREE@[28; 39)
-            L_BRACK@[28; 29) "["
-            IDENT@[29; 32) "cfg"
-            TOKEN_TREE@[32; 38)
-              L_PAREN@[32; 33) "("
-              IDENT@[33; 37) "test"
-              R_PAREN@[37; 38) ")"
-            R_BRACK@[38; 39) "]"
-        WHITESPACE@[39; 42) "\n  "
-        LITERAL@[42; 43)
-          INT_NUMBER@[42; 43) "1"
-        SEMI@[43; 44) ";"
-        WHITESPACE@[44; 47) "\n  "
-        LITERAL@[47; 48)
-          INT_NUMBER@[47; 48) "2"
-  ERROR@[48; 49)
-    COMMA@[48; 49) ","
-  WHITESPACE@[49; 50) "\n"
-  ERROR@[50; 51)
-    R_BRACK@[50; 51) "]"
-  ERROR@[51; 52)
-    SEMI@[51; 52) ";"
-  WHITESPACE@[52; 53) "\n"
-error 44: removing an expression is not supported in this position
-error 48: expected R_BRACK
-error 48: expected SEMI
-error 48: expected an item
-error 50: expected an item
-error 51: expected an item