Merge #10085

10085: fix: avoid panic when parsing extern block r=matklad a=matklad

bors r+
🤖

Co-authored-by: Aleksey Kladov <aleksey.kladov@gmail.com>

crates/syntax/test_data/parser/err/0048_repated_extern_modifier.rast

@@ -0,0 +1,15 @@
+SOURCE_FILE@0..22
+  ERROR@0..10
+    ABI@0..10
+      EXTERN_KW@0..6 "extern"
+      WHITESPACE@6..7 " "
+      STRING@7..10 "\"C\""
+  WHITESPACE@10..11 " "
+  ERROR@11..21
+    ABI@11..21
+      EXTERN_KW@11..17 "extern"
+      WHITESPACE@17..18 " "
+      STRING@18..21 "\"C\""
+  WHITESPACE@21..22 "\n"
+error 10..10: expected existential, fn, trait or impl
+error 21..21: expected existential, fn, trait or impl

crates/syntax/test_data/parser/err/0048_repated_extern_modifier.rs

@@ -0,0 +1 @@
+extern "C" extern "C"

crates/syntax/test_data/parser/inline/ok/0010_extern_block.rast

@@ -1,9 +1,21 @@
-SOURCE_FILE@0..10
-  EXTERN_BLOCK@0..9
-    ABI@0..6
-      EXTERN_KW@0..6 "extern"
+SOURCE_FILE@0..31
+  EXTERN_BLOCK@0..20
+    UNSAFE_KW@0..6 "unsafe"
     WHITESPACE@6..7 " "
-    EXTERN_ITEM_LIST@7..9
-      L_CURLY@7..8 "{"
-      R_CURLY@8..9 "}"
-  WHITESPACE@9..10 "\n"
+    ABI@7..17
+      EXTERN_KW@7..13 "extern"
+      WHITESPACE@13..14 " "
+      STRING@14..17 "\"C\""
+    WHITESPACE@17..18 " "
+    EXTERN_ITEM_LIST@18..20
+      L_CURLY@18..19 "{"
+      R_CURLY@19..20 "}"
+  WHITESPACE@20..21 "\n"
+  EXTERN_BLOCK@21..30
+    ABI@21..27
+      EXTERN_KW@21..27 "extern"
+    WHITESPACE@27..28 " "
+    EXTERN_ITEM_LIST@28..30
+      L_CURLY@28..29 "{"
+      R_CURLY@29..30 "}"
+  WHITESPACE@30..31 "\n"

crates/syntax/test_data/parser/inline/ok/0010_extern_block.rs

@@ -1 +1,2 @@
+unsafe extern "C" {}
 extern {}