From fc29d8360440c39cd1934c1a5f3995c6c069d6a5 Mon Sep 17 00:00:00 2001
From: kojix2 <2xijok@gmail.com>
Date: Mon, 6 Apr 2026 22:35:42 +0900
Subject: [PATCH 1/3] Return early on generic args in non-raising lookup

Fix #14731
---
 src/compiler/crystal/semantic/type_lookup.cr | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/compiler/crystal/semantic/type_lookup.cr b/src/compiler/crystal/semantic/type_lookup.cr
index fc7d9db2e57a..09a5a4b10eca 100644
--- a/src/compiler/crystal/semantic/type_lookup.cr
+++ b/src/compiler/crystal/semantic/type_lookup.cr
@@ -253,7 +253,7 @@ class Crystal::Type
           end
           next
         when SizeOf, InstanceSizeOf, AlignOf, InstanceAlignOf, OffsetOf
-          next unless @raise
+          return unless @raise
 
           type_var.raise "can't use #{type_var} as a generic type argument"
         end

From d172bb374567c956141d9f84ba15c6465da1b3e2 Mon Sep 17 00:00:00 2001
From: kojix2 <2xijok@gmail.com>
Date: Mon, 6 Apr 2026 22:36:26 +0900
Subject: [PATCH 2/3] Add tests

---
 spec/compiler/semantic/generic_class_spec.cr | 41 ++++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/spec/compiler/semantic/generic_class_spec.cr b/spec/compiler/semantic/generic_class_spec.cr
index 5c094ad0c63f..5cb598f541e8 100644
--- a/spec/compiler/semantic/generic_class_spec.cr
+++ b/spec/compiler/semantic/generic_class_spec.cr
@@ -1362,4 +1362,45 @@ describe "Semantic: generic class" do
       Bar(Int32).new.@foo
       CRYSTAL
   end
+
+  it "doesn't crash on sizeof in inferred ivar type (#14731)" do
+    assert_error <<-CRYSTAL, "can't infer the type of instance variable '@x' of Bar(T)"
+      class Foo(N)
+      end
+
+      class Bar(T)
+        @x = Foo(sizeof(T)).new
+      end
+      CRYSTAL
+  end
+
+  it "doesn't crash on offsetof in inferred ivar type (#14731)" do
+    assert_error <<-CRYSTAL, "can't infer the type of instance variable '@x' of Bar(T)"
+      class Foo(N)
+      end
+
+      struct SomeStruct
+        @field : Int32 = 0
+      end
+
+      class Bar(T)
+        @x = Foo(offsetof(SomeStruct, @field)).new
+      end
+      CRYSTAL
+  end
+
+  it "doesn't crash on sizeof in initialize ivar assignment (#14731)" do
+    assert_error <<-CRYSTAL, "can't infer the type of instance variable '@x' of Bar(Int32)"
+      class Foo(N)
+      end
+
+      class Bar(T)
+        def initialize
+          @x = Foo(sizeof(T)).new
+        end
+      end
+
+      Bar(Int32).new
+      CRYSTAL
+  end
 end

From df634911eee2bef052282312a001aa50e2b28ccc Mon Sep 17 00:00:00 2001
From: kojix2 <2xijok@gmail.com>
Date: Wed, 8 Apr 2026 21:03:07 +0900
Subject: [PATCH 3/3] Revert "Add tests"

It has been proposed to allow integer expressions and `sizeof()` as part
of type notation.(#5427)

This reverts commit d172bb374567c956141d9f84ba15c6465da1b3e2.
---
 spec/compiler/semantic/generic_class_spec.cr | 41 --------------------
 1 file changed, 41 deletions(-)

diff --git a/spec/compiler/semantic/generic_class_spec.cr b/spec/compiler/semantic/generic_class_spec.cr
index 5cb598f541e8..5c094ad0c63f 100644
--- a/spec/compiler/semantic/generic_class_spec.cr
+++ b/spec/compiler/semantic/generic_class_spec.cr
@@ -1362,45 +1362,4 @@ describe "Semantic: generic class" do
       Bar(Int32).new.@foo
       CRYSTAL
   end
-
-  it "doesn't crash on sizeof in inferred ivar type (#14731)" do
-    assert_error <<-CRYSTAL, "can't infer the type of instance variable '@x' of Bar(T)"
-      class Foo(N)
-      end
-
-      class Bar(T)
-        @x = Foo(sizeof(T)).new
-      end
-      CRYSTAL
-  end
-
-  it "doesn't crash on offsetof in inferred ivar type (#14731)" do
-    assert_error <<-CRYSTAL, "can't infer the type of instance variable '@x' of Bar(T)"
-      class Foo(N)
-      end
-
-      struct SomeStruct
-        @field : Int32 = 0
-      end
-
-      class Bar(T)
-        @x = Foo(offsetof(SomeStruct, @field)).new
-      end
-      CRYSTAL
-  end
-
-  it "doesn't crash on sizeof in initialize ivar assignment (#14731)" do
-    assert_error <<-CRYSTAL, "can't infer the type of instance variable '@x' of Bar(Int32)"
-      class Foo(N)
-      end
-
-      class Bar(T)
-        def initialize
-          @x = Foo(sizeof(T)).new
-        end
-      end
-
-      Bar(Int32).new
-      CRYSTAL
-  end
 end