From b1996aee5c3e9fab7c47d3e1a6395baac7492e79 Mon Sep 17 00:00:00 2001
From: ringabout <43030857+ringabout@users.noreply.github.com>
Date: Tue, 6 Dec 2022 20:09:50 +0800
Subject: [PATCH] fixes #21027; cast expressions need a type (#21029)

* fixes #21027; cast expressions need a type

* Apply suggestions from code review

Thanks to @beef331

(cherry picked from commit 1564ae650f8d4d4c30adf4528f74d7707e4cb737)
---
 compiler/semexprs.nim  | 2 ++
 tests/types/t21027.nim | 5 +++++
 2 files changed, 7 insertions(+)
 create mode 100644 tests/types/t21027.nim

diff --git a/compiler/semexprs.nim b/compiler/semexprs.nim
index 2c1d40ff2523f..de2259eb4f786 100644
--- a/compiler/semexprs.nim
+++ b/compiler/semexprs.nim
@@ -361,6 +361,8 @@ proc semCast(c: PContext, n: PNode): PNode =
   let castedExpr = semExprWithType(c, n[1])
   if castedExpr.kind == nkClosedSymChoice:
     errorUseQualifier(c, n[1].info, castedExpr)
+  if targetType == nil:
+    localError(c.config, n.info, "Invalid usage of cast, cast requires a type to convert to, e.g., cast[int](0d).")
   if tfHasMeta in targetType.flags:
     localError(c.config, n[0].info, "cannot cast to a non concrete type: '$1'" % $targetType)
   if not isCastable(c, targetType, castedExpr.typ, n.info):
diff --git a/tests/types/t21027.nim b/tests/types/t21027.nim
new file mode 100644
index 0000000000000..3a992177a43a1
--- /dev/null
+++ b/tests/types/t21027.nim
@@ -0,0 +1,5 @@
+discard """
+  errormsg: "Invalid usage of cast, cast requires a type to convert to, e.g., cast[int](0d)."
+"""
+# bug #21027
+let x: uint64 = cast(5)