From adcaad6d91c309fab20ea208231c3e7d33fcc21f Mon Sep 17 00:00:00 2001
From: dweiller <4678790+dweiller@users.noreply.github.com>
Date: Fri, 1 Dec 2023 15:41:28 +1100
Subject: [PATCH] sema: fix err union switch with inferred empty error sets

---
 src/Sema.zig | 79 ++++++++++++++++++++++++++++------------------------
 1 file changed, 42 insertions(+), 37 deletions(-)

diff --git a/src/Sema.zig b/src/Sema.zig
index 752bc4da6f9629240a96819d8149bd145e0cca71..eebf31a2389d1589e9d4bfa3431a9f21a6854459 100644
--- a/src/Sema.zig
+++ b/src/Sema.zig
@@ -11237,6 +11237,48 @@ fn zirSwitchBlockErrUnion(sema: *Sema, block: *Block, inst: Zir.Inst.Index) Comp
     const operand_ty = sema.typeOf(raw_operand_val);
     const operand_err_set_ty = operand_ty.errorUnionSet(mod);
 
+    const block_inst: Air.Inst.Index = @enumFromInt(sema.air_instructions.len);
+    try sema.air_instructions.append(gpa, .{
+        .tag = .block,
+        .data = undefined,
+    });
+    var label: Block.Label = .{
+        .zir_block = inst,
+        .merges = .{
+            .src_locs = .{},
+            .results = .{},
+            .br_list = .{},
+            .block_inst = block_inst,
+        },
+    };
+
+    var child_block: Block = .{
+        .parent = block,
+        .sema = sema,
+        .src_decl = block.src_decl,
+        .namespace = block.namespace,
+        .wip_capture_scope = block.wip_capture_scope,
+        .instructions = .{},
+        .label = &label,
+        .inlining = block.inlining,
+        .is_comptime = block.is_comptime,
+        .comptime_reason = block.comptime_reason,
+        .is_typeof = block.is_typeof,
+        .c_import_buf = block.c_import_buf,
+        .runtime_cond = block.runtime_cond,
+        .runtime_loop = block.runtime_loop,
+        .runtime_index = block.runtime_index,
+        .error_return_trace_index = block.error_return_trace_index,
+    };
+    const merges = &child_block.label.?.merges;
+    defer child_block.instructions.deinit(gpa);
+    defer merges.deinit(gpa);
+
+    const resolved_err_set = try sema.resolveInferredErrorSetTy(block, src, operand_err_set_ty.toIntern());
+    if (Type.fromInterned(resolved_err_set).errorSetIsEmpty(mod)) {
+        return sema.resolveBlockBody(block, operand_src, &child_block, non_error_case.body, inst, merges);
+    }
+
     const else_error_ty: ?Type = try validateErrSetSwitch(
         sema,
         block,
@@ -11261,43 +11303,6 @@ fn zirSwitchBlockErrUnion(sema: *Sema, block: *Block, inst: Zir.Inst.Index) Comp
         .tag_capture_inst = undefined,
     };
 
-    const block_inst: Air.Inst.Index = @enumFromInt(sema.air_instructions.len);
-    try sema.air_instructions.append(gpa, .{
-        .tag = .block,
-        .data = undefined,
-    });
-    var label: Block.Label = .{
-        .zir_block = inst,
-        .merges = .{
-            .src_locs = .{},
-            .results = .{},
-            .br_list = .{},
-            .block_inst = block_inst,
-        },
-    };
-
-    var child_block: Block = .{
-        .parent = block,
-        .sema = sema,
-        .src_decl = block.src_decl,
-        .namespace = block.namespace,
-        .wip_capture_scope = block.wip_capture_scope,
-        .instructions = .{},
-        .label = &label,
-        .inlining = block.inlining,
-        .is_comptime = block.is_comptime,
-        .comptime_reason = block.comptime_reason,
-        .is_typeof = block.is_typeof,
-        .c_import_buf = block.c_import_buf,
-        .runtime_cond = block.runtime_cond,
-        .runtime_loop = block.runtime_loop,
-        .runtime_index = block.runtime_index,
-        .error_return_trace_index = block.error_return_trace_index,
-    };
-    const merges = &child_block.label.?.merges;
-    defer child_block.instructions.deinit(gpa);
-    defer merges.deinit(gpa);
-
     if (try sema.resolveDefinedValue(&child_block, src, raw_operand_val)) |operand_val| {
         if (operand_val.errorUnionIsPayload(mod)) {
             return sema.resolveBlockBody(block, operand_src, &child_block, non_error_case.body, inst, merges);
-- 
2.54.0