feat(semantic): report error on optional variable declaration in TypeScript (#2261)

closes #2253
closes #2255

crates/oxc_semantic/src/checker/typescript.rs

@@ -16,9 +16,8 @@ impl EarlyErrorTypeScript {
     pub fn run<'a>(node: &AstNode<'a>, ctx: &SemanticBuilder<'a>) {
         let kind = node.kind();
 
-        // should be removed when add more matches.
-        #[allow(clippy::single_match)]
         match kind {
+            AstKind::VariableDeclarator(decl) => check_variable_declarator(decl, ctx),
             AstKind::SimpleAssignmentTarget(target) => check_simple_assignment_target(target, ctx),
             AstKind::FormalParameters(params) => check_formal_parameters(params, ctx),
             _ => {}
@@ -26,6 +25,20 @@ impl EarlyErrorTypeScript {
     }
 }
 
+#[allow(clippy::cast_possible_truncation)]
+fn check_variable_declarator(decl: &VariableDeclarator, ctx: &SemanticBuilder<'_>) {
+    #[derive(Debug, Error, Diagnostic)]
+    #[error("Unexpected `?` operator")]
+    #[diagnostic()]
+    struct UnexpectedOptional(#[label] Span);
+    if decl.id.optional {
+        let start = decl.id.span().end;
+        let Some(offset) = ctx.source_text[start as usize..].find('?') else { return };
+        let offset = start + offset as u32;
+        ctx.error(UnexpectedOptional(Span::new(offset, offset)));
+    }
+}
+
 fn check_formal_parameters(params: &FormalParameters, ctx: &SemanticBuilder<'_>) {
     if !params.is_empty() && params.kind == FormalParameterKind::Signature {
         check_duplicate_bound_names(params, ctx);

tasks/coverage/misc/fail/oxc-2253.ts

@@ -0,0 +1,7 @@
+const a? = "A"
+const [b]? = ["B"]
+const { c }? = { c: "C" }
+
+const d     ? = "A"
+const [e, f]      ? = ["B"]
+const { g, h }       ? = { c: "C" }

tasks/coverage/parser_misc.snap

@@ -1,7 +1,7 @@
 parser_misc Summary:
 AST Parsed     : 10/10 (100.00%)
 Positive Passed: 10/10 (100.00%)
-Negative Passed: 5/5 (100.00%)
+Negative Passed: 6/6 (100.00%)
   × Unexpected token
    ╭─[fail/oxc-169.js:1:1]
  1 │ 1<(V=82<<t-j0<(V=$<LBI<(V=ut<I<(V=$<LBI<(V=uIV=82<<t-j0<(V=$<LBI<(V=ut<I<(V=$<LBI<(V<II>
@@ -23,6 +23,52 @@ Negative Passed: 5/5 (100.00%)
  3 │ }
    ╰────
 
+  × Unexpected `?` operator
+   ╭─[fail/oxc-2253.ts:1:1]
+ 1 │ const a? = "A"
+   ·        ▲
+ 2 │ const [b]? = ["B"]
+   ╰────
+
+  × Unexpected `?` operator
+   ╭─[fail/oxc-2253.ts:1:1]
+ 1 │ const a? = "A"
+ 2 │ const [b]? = ["B"]
+   ·          ▲
+ 3 │ const { c }? = { c: "C" }
+   ╰────
+
+  × Unexpected `?` operator
+   ╭─[fail/oxc-2253.ts:2:1]
+ 2 │ const [b]? = ["B"]
+ 3 │ const { c }? = { c: "C" }
+   ·            ▲
+ 4 │ 
+   ╰────
+
+  × Unexpected `?` operator
+   ╭─[fail/oxc-2253.ts:4:1]
+ 4 │ 
+ 5 │ const d     ? = "A"
+   ·             ▲
+ 6 │ const [e, f]      ? = ["B"]
+   ╰────
+
+  × Unexpected `?` operator
+   ╭─[fail/oxc-2253.ts:5:1]
+ 5 │ const d     ? = "A"
+ 6 │ const [e, f]      ? = ["B"]
+   ·                   ▲
+ 7 │ const { g, h }       ? = { c: "C" }
+   ╰────
+
+  × Unexpected `?` operator
+   ╭─[fail/oxc-2253.ts:6:1]
+ 6 │ const [e, f]      ? = ["B"]
+ 7 │ const { g, h }       ? = { c: "C" }
+   ·                      ▲
+   ╰────
+
   × Empty parenthesized expression
    ╭─[fail/oxc-232.js:1:1]
  1 │ x = (/* a */)