diff --git a/tasks/coverage/misc/fail/oxc-18231.mjs b/tasks/coverage/misc/fail/oxc-18231.mjs
new file mode 100644
index 0000000000000..bc3e2a81bff3c
--- /dev/null
+++ b/tasks/coverage/misc/fail/oxc-18231.mjs
@@ -0,0 +1,5 @@
+function f() {}
+function f() {}
+
+var g;
+function g() {}
diff --git a/tasks/coverage/misc/pass/oxc-18231.cjs b/tasks/coverage/misc/pass/oxc-18231.cjs
new file mode 100644
index 0000000000000..bc3e2a81bff3c
--- /dev/null
+++ b/tasks/coverage/misc/pass/oxc-18231.cjs
@@ -0,0 +1,5 @@
+function f() {}
+function f() {}
+
+var g;
+function g() {}
diff --git a/tasks/coverage/misc/pass/oxc-18231.js b/tasks/coverage/misc/pass/oxc-18231.js
new file mode 100644
index 0000000000000..bc3e2a81bff3c
--- /dev/null
+++ b/tasks/coverage/misc/pass/oxc-18231.js
@@ -0,0 +1,5 @@
+function f() {}
+function f() {}
+
+var g;
+function g() {}
diff --git a/tasks/coverage/snapshots/codegen_misc.snap b/tasks/coverage/snapshots/codegen_misc.snap
index 431f60bb77197..e8cc6977d765c 100644
--- a/tasks/coverage/snapshots/codegen_misc.snap
+++ b/tasks/coverage/snapshots/codegen_misc.snap
@@ -1,3 +1,3 @@
 codegen_misc Summary:
-AST Parsed     : 62/62 (100.00%)
-Positive Passed: 62/62 (100.00%)
+AST Parsed     : 64/64 (100.00%)
+Positive Passed: 64/64 (100.00%)
diff --git a/tasks/coverage/snapshots/formatter_misc.snap b/tasks/coverage/snapshots/formatter_misc.snap
index 439606723ae4d..420c9be986ebe 100644
--- a/tasks/coverage/snapshots/formatter_misc.snap
+++ b/tasks/coverage/snapshots/formatter_misc.snap
@@ -1,3 +1,3 @@
 formatter_misc Summary:
-AST Parsed     : 62/62 (100.00%)
-Positive Passed: 62/62 (100.00%)
+AST Parsed     : 64/64 (100.00%)
+Positive Passed: 64/64 (100.00%)
diff --git a/tasks/coverage/snapshots/parser_misc.snap b/tasks/coverage/snapshots/parser_misc.snap
index c42aa110adada..ebce7d0fa0695 100644
--- a/tasks/coverage/snapshots/parser_misc.snap
+++ b/tasks/coverage/snapshots/parser_misc.snap
@@ -1,7 +1,7 @@
 parser_misc Summary:
-AST Parsed     : 62/62 (100.00%)
-Positive Passed: 62/62 (100.00%)
-Negative Passed: 130/130 (100.00%)
+AST Parsed     : 64/64 (100.00%)
+Positive Passed: 64/64 (100.00%)
+Negative Passed: 131/131 (100.00%)
 
   × Cannot assign to 'arguments' in strict mode
    ╭─[misc/fail/arguments-eval.ts:1:10]
@@ -3394,6 +3394,28 @@ Negative Passed: 130/130 (100.00%)
  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>
    ╰────
 
+  × Identifier `f` has already been declared
+   ╭─[misc/fail/oxc-18231.mjs:1:10]
+ 1 │ function f() {}
+   ·          ┬
+   ·          ╰── `f` has already been declared here
+ 2 │ function f() {}
+   ·          ┬
+   ·          ╰── It can not be redeclared here
+ 3 │ 
+   ╰────
+
+  × Identifier `g` has already been declared
+   ╭─[misc/fail/oxc-18231.mjs:4:5]
+ 3 │ 
+ 4 │ var g;
+   ·     ┬
+   ·     ╰── `g` has already been declared here
+ 5 │ function g() {}
+   ·          ┬
+   ·          ╰── It can not be redeclared here
+   ╰────
+
   × Expected `(` but found `:`
    ╭─[misc/fail/oxc-1942-1.ts:2:8]
  1 │ class Foo {
diff --git a/tasks/coverage/snapshots/semantic_misc.snap b/tasks/coverage/snapshots/semantic_misc.snap
index 36bfd694693ea..9e861feed9473 100644
--- a/tasks/coverage/snapshots/semantic_misc.snap
+++ b/tasks/coverage/snapshots/semantic_misc.snap
@@ -1,6 +1,6 @@
 semantic_misc Summary:
-AST Parsed     : 62/62 (100.00%)
-Positive Passed: 43/62 (69.35%)
+AST Parsed     : 64/64 (100.00%)
+Positive Passed: 45/64 (70.31%)
 semantic Error: tasks/coverage/misc/pass/declare-let-private.ts
 Bindings mismatch:
 after transform: ScopeId(0): ["private"]
diff --git a/tasks/coverage/snapshots/transformer_misc.snap b/tasks/coverage/snapshots/transformer_misc.snap
index 0383684db649a..56ef1c69aa893 100644
--- a/tasks/coverage/snapshots/transformer_misc.snap
+++ b/tasks/coverage/snapshots/transformer_misc.snap
@@ -1,5 +1,5 @@
 transformer_misc Summary:
-AST Parsed     : 62/62 (100.00%)
-Positive Passed: 61/62 (98.39%)
+AST Parsed     : 64/64 (100.00%)
+Positive Passed: 63/64 (98.44%)
 Mismatch: tasks/coverage/misc/pass/babel-16776-s.js