From 8e4d0ae4f5c50621a402192f2ff7f9b156030257 Mon Sep 17 00:00:00 2001
From: Veikka Tuominen <git@vexu.eu>
Date: Sat, 24 Sep 2022 00:08:42 +0300
Subject: [PATCH] Sema: avoid generic parameter error in nested function type

Related to cd1833044ab7505bc101c85f59889bd3ea3fac80
Closes #12945
---
 src/Sema.zig                 |  4 ++--
 test/behavior.zig            |  1 +
 test/behavior/bugs/12945.zig | 13 +++++++++++++
 3 files changed, 16 insertions(+), 2 deletions(-)
 create mode 100644 test/behavior/bugs/12945.zig

diff --git a/src/Sema.zig b/src/Sema.zig
index 81447d6361..a36e1d9a02 100644
--- a/src/Sema.zig
+++ b/src/Sema.zig
@@ -8180,7 +8180,7 @@ fn analyzeParameter(
     if (param.is_comptime and !Type.fnCallingConventionAllowsZigTypes(cc)) {
         return sema.fail(block, param_src, "comptime parameters not allowed in function with calling convention '{s}'", .{@tagName(cc)});
     }
-    if (this_generic and !Type.fnCallingConventionAllowsZigTypes(cc)) {
+    if (this_generic and !sema.no_partial_func_ty and !Type.fnCallingConventionAllowsZigTypes(cc)) {
         return sema.fail(block, param_src, "generic parameters not allowed in function with calling convention '{s}'", .{@tagName(cc)});
     }
     if (!param.ty.isValidParamType()) {
@@ -8196,7 +8196,7 @@ fn analyzeParameter(
         };
         return sema.failWithOwnedErrorMsg(msg);
     }
-    if (!Type.fnCallingConventionAllowsZigTypes(cc) and !try sema.validateExternType(block, param_src, param.ty, .param_ty)) {
+    if (!this_generic and !Type.fnCallingConventionAllowsZigTypes(cc) and !try sema.validateExternType(block, param_src, param.ty, .param_ty)) {
         const msg = msg: {
             const msg = try sema.errMsg(block, param_src, "parameter of type '{}' not allowed in function with calling convention '{s}'", .{
                 param.ty.fmt(sema.mod), @tagName(cc),
diff --git a/test/behavior.zig b/test/behavior.zig
index a4acb57124..648757d56f 100644
--- a/test/behavior.zig
+++ b/test/behavior.zig
@@ -96,6 +96,7 @@ test {
     _ = @import("behavior/bugs/12885.zig");
     _ = @import("behavior/bugs/12911.zig");
     _ = @import("behavior/bugs/12928.zig");
+    _ = @import("behavior/bugs/12945.zig");
     _ = @import("behavior/byteswap.zig");
     _ = @import("behavior/byval_arg_var.zig");
     _ = @import("behavior/call.zig");
diff --git a/test/behavior/bugs/12945.zig b/test/behavior/bugs/12945.zig
new file mode 100644
index 0000000000..4eb7701ba4
--- /dev/null
+++ b/test/behavior/bugs/12945.zig
@@ -0,0 +1,13 @@
+const std = @import("std");
+const expect = std.testing.expect;
+
+fn A(
+    comptime T: type,
+    comptime destroycb: ?*const fn (?*T) callconv(.C) void,
+) !void {
+    try expect(destroycb == null);
+}
+
+test {
+    try A(u32, null);
+}