Fix panic during malformed empty interpolated string

CHANGELOG.md

@@ -9,6 +9,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 - Luau: added support for user defined type functions (rfc: https://github.com/luau-lang/rfcs/blob/master/docs/user-defined-type-functions.md)
 
+### Fixed
+- Fixed a panic when parsing a malformed empty interpolated string, e.g. ``print(`{}`)``
+
 ## [1.1.2] - 2024-11-17
 
 ### Fixed

full-moon/src/ast/parsers.rs

@@ -1767,7 +1767,7 @@ fn parse_primary_expression(state: &mut ParserState) -> ParserResult<Expression>
                     ))
                 }
 
-                other => unreachable!("unexpected interpolated string kind: {other:?}"),
+                _ => ParserResult::NotFound,
             }
         }
 

full-moon/tests/roblox_cases/fail/parser/string_interpolation_empty/ast.snap

@@ -0,0 +1,94 @@
+---
+source: full-moon/tests/fail_cases.rs
+expression: result.ast()
+input_file: full-moon/tests/roblox_cases/fail/parser/string_interpolation_empty
+---
+nodes:
+  stmts:
+    - - FunctionCall:
+          prefix:
+            Name:
+              leading_trivia: []
+              token:
+                start_position:
+                  bytes: 0
+                  line: 1
+                  character: 1
+                end_position:
+                  bytes: 5
+                  line: 1
+                  character: 6
+                token_type:
+                  type: Identifier
+                  identifier: print
+              trailing_trivia: []
+          suffixes:
+            - Call:
+                AnonymousCall:
+                  Parentheses:
+                    parentheses:
+                      tokens:
+                        - leading_trivia: []
+                          token:
+                            start_position:
+                              bytes: 5
+                              line: 1
+                              character: 6
+                            end_position:
+                              bytes: 6
+                              line: 1
+                              character: 7
+                            token_type:
+                              type: Symbol
+                              symbol: (
+                          trailing_trivia: []
+                        - leading_trivia: []
+                          token:
+                            start_position:
+                              bytes: 10
+                              line: 1
+                              character: 11
+                            end_position:
+                              bytes: 11
+                              line: 1
+                              character: 12
+                            token_type:
+                              type: Symbol
+                              symbol: )
+                          trailing_trivia: []
+                    arguments:
+                      pairs:
+                        - End:
+                            InterpolatedString:
+                              segments: []
+                              last_string:
+                                leading_trivia: []
+                                token:
+                                  start_position:
+                                    bytes: 6
+                                    line: 1
+                                    character: 7
+                                  end_position:
+                                    bytes: 8
+                                    line: 1
+                                    character: 9
+                                  token_type:
+                                    type: InterpolatedString
+                                    literal: ""
+                                    kind: Begin
+                                trailing_trivia: []
+      - ~
+eof:
+  leading_trivia: []
+  token:
+    start_position:
+      bytes: 11
+      line: 1
+      character: 12
+    end_position:
+      bytes: 11
+      line: 1
+      character: 12
+    token_type:
+      type: Eof
+  trailing_trivia: []

full-moon/tests/roblox_cases/fail/parser/string_interpolation_empty/ast_to_string.snap

@@ -0,0 +1,6 @@
+---
+source: full-moon/tests/fail_cases.rs
+expression: ast.to_string()
+input_file: full-moon/tests/roblox_cases/fail/parser/string_interpolation_empty
+---
+"print(`{)"

full-moon/tests/roblox_cases/fail/parser/string_interpolation_empty/error_display.snap

@@ -0,0 +1,10 @@
+---
+source: full-moon/tests/fail_cases.rs
+expression: "String::from_utf8(output.into_inner()).unwrap()"
+input_file: full-moon/tests/roblox_cases/fail/parser/string_interpolation_empty
+---
+error[ast]: expected expression after `{`
+  ┌─ source.lua:1:7
+  │
+1 │ print(`{}`)
+  │       ^^

full-moon/tests/roblox_cases/fail/parser/string_interpolation_empty/errors.snap

@@ -0,0 +1,20 @@
+---
+source: full-moon/tests/fail_cases.rs
+expression: result.errors()
+input_file: full-moon/tests/roblox_cases/fail/parser/string_interpolation_empty
+---
+- AstError:
+    token:
+      start_position:
+        bytes: 6
+        line: 1
+        character: 7
+      end_position:
+        bytes: 8
+        line: 1
+        character: 9
+      token_type:
+        type: InterpolatedString
+        literal: ""
+        kind: Begin
+    additional: "expected expression after `{`"

full-moon/tests/roblox_cases/fail/parser/string_interpolation_empty/source.lua

@@ -0,0 +1 @@
+print(`{}`)

full-moon/tests/roblox_cases/fail/parser/string_interpolation_empty/tokens.snap

@@ -0,0 +1,72 @@
+---
+source: full-moon/tests/fail_cases.rs
+expression: tokens
+input_file: full-moon/tests/roblox_cases/fail/parser/string_interpolation_empty
+---
+- start_position:
+    bytes: 0
+    line: 1
+    character: 1
+  end_position:
+    bytes: 5
+    line: 1
+    character: 6
+  token_type:
+    type: Identifier
+    identifier: print
+- start_position:
+    bytes: 5
+    line: 1
+    character: 6
+  end_position:
+    bytes: 6
+    line: 1
+    character: 7
+  token_type:
+    type: Symbol
+    symbol: (
+- start_position:
+    bytes: 6
+    line: 1
+    character: 7
+  end_position:
+    bytes: 8
+    line: 1
+    character: 9
+  token_type:
+    type: InterpolatedString
+    literal: ""
+    kind: Begin
+- start_position:
+    bytes: 8
+    line: 1
+    character: 9
+  end_position:
+    bytes: 10
+    line: 1
+    character: 11
+  token_type:
+    type: InterpolatedString
+    literal: ""
+    kind: End
+- start_position:
+    bytes: 10
+    line: 1
+    character: 11
+  end_position:
+    bytes: 11
+    line: 1
+    character: 12
+  token_type:
+    type: Symbol
+    symbol: )
+- start_position:
+    bytes: 11
+    line: 1
+    character: 12
+  end_position:
+    bytes: 11
+    line: 1
+    character: 12
+  token_type:
+    type: Eof