From ffc5242169d67840e0d1420b792696fc1b3d1722 Mon Sep 17 00:00:00 2001
From: Matthew Lugg <mlugg@mlugg.co.uk>
Date: Sun, 8 Feb 2026 14:04:51 +0000
Subject: [PATCH] Sema: small NPV fixes

---
 src/Sema.zig | 12 +-----------
 src/Type.zig | 24 +++++++++++++++++++++---
 2 files changed, 22 insertions(+), 14 deletions(-)

diff --git a/src/Sema.zig b/src/Sema.zig
index b0271ffde0..140e69fe6f 100644
--- a/src/Sema.zig
+++ b/src/Sema.zig
@@ -19400,7 +19400,7 @@ fn zirAlignOf(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError!Air
     const ty = try sema.resolveType(block, operand_src, inst_data.operand);
     try sema.ensureLayoutResolved(ty, operand_src, .align_of);
     if (ty.isNoReturn(zcu)) {
-        return sema.fail(block, operand_src, "no align available for type '{f}'", .{ty.fmt(sema.pt)});
+        return sema.fail(block, operand_src, "no align available for uninstantiable type '{f}'", .{ty.fmt(sema.pt)});
     }
     return .fromValue(try pt.intValue(.comptime_int, ty.abiAlignment(zcu).toByteUnits().?));
 }
@@ -33432,16 +33432,6 @@ fn errorSetMerge(sema: *Sema, lhs: Type, rhs: Type) !Type {
     return pt.errorSetFromUnsortedNames(names.keys());
 }
 
-/// Avoids crashing the compiler when asking if inferred allocations are noreturn.
-fn isNoReturn(sema: *Sema, ref: Air.Inst.Ref) bool {
-    if (ref == .unreachable_value) return true;
-    if (ref.toIndex()) |inst| switch (sema.air_instructions.items(.tag)[@intFromEnum(inst)]) {
-        .inferred_alloc, .inferred_alloc_comptime => return false,
-        else => {},
-    };
-    return sema.typeOf(ref).isNoReturn(sema.pt.zcu);
-}
-
 pub fn declareDependency(sema: *Sema, dependee: InternPool.Dependee) !void {
     const pt = sema.pt;
     if (!pt.zcu.comp.config.incremental) return;
diff --git a/src/Type.zig b/src/Type.zig
index 3eb14f3b53..2348503765 100644
--- a/src/Type.zig
+++ b/src/Type.zig
@@ -790,11 +790,21 @@ pub fn hasWellDefinedLayout(ty: Type, zcu: *const Zcu) bool {
 /// function with this type can exist at runtime.
 /// Asserts that `ty` is a function type.
 pub fn fnHasRuntimeBits(fn_ty: Type, zcu: *Zcu) bool {
+    assertHasLayout(fn_ty, zcu);
     const fn_info = zcu.typeToFunc(fn_ty).?;
     if (fn_info.comptime_bits != 0) return false;
     for (fn_info.param_types.get(&zcu.intern_pool)) |param_ty| {
         if (param_ty == .generic_poison_type) return false;
-        if (Type.fromInterned(param_ty).comptimeOnly(zcu)) return false;
+        switch (Type.fromInterned(param_ty).classify(zcu)) {
+            .fully_comptime,
+            .partially_comptime,
+            .no_possible_value,
+            => return false,
+
+            .one_possible_value,
+            .runtime,
+            => {},
+        }
     }
     const ret_ty: Type = .fromInterned(fn_info.return_type);
     if (ret_ty.toIntern() == .generic_poison_type) {
@@ -805,8 +815,16 @@ pub fn fnHasRuntimeBits(fn_ty: Type, zcu: *Zcu) bool {
     {
         return false;
     }
-    if (fn_info.return_type == .generic_poison_type) return false;
-    if (Type.fromInterned(fn_info.return_type).comptimeOnly(zcu)) return false;
+    switch (ret_ty.classify(zcu)) {
+        .fully_comptime,
+        .partially_comptime,
+        => return false,
+
+        .no_possible_value,
+        .one_possible_value,
+        .runtime,
+        => {},
+    }
     if (fn_info.cc == .@"inline") return false;
     return true;
 }