Commit 252c2031011f80b35d01d5ba5a2a2577c870f90c | zig

author	Matthew Lugg <mlugg@mlugg.co.uk> 2025-01-01 21:59:55+00:00
committer	Matthew Lugg <mlugg@mlugg.co.uk> 2025-01-02 16:26:50+00:00
log	252c2031011f80b35d01d5ba5a2a2577c870f90c
tree	9c7ed95ecf01033b19bce941df2b320cb34dc376
parent	e6879e99e26fd11f659be3deec2b5de409b46547

Sema: correctly label `block_comptime` for restoring error return trace index

Resolves: #22384

2 files changed, 19 insertions(+), 6 deletions(-)

src
- Sema.zig
test
- behavior
  - eval.zig

src/Sema.zig+12-6

 @@ -1658,13 +1658,17 @@ fn analyzeBodyInner(
                 const extra = sema.code.extraData(Zir.Inst.BlockComptime, pl_node.payload_index);
                 const block_body = sema.code.bodySlice(extra.end, extra.data.body_len);
-                if (block.isComptime()) {
-                    // No need for a sub-block; just resolve the other body directly!
-                    break :inst try sema.resolveInlineBody(block, block_body, inst);
-                }
                 var child_block = block.makeSubBlock();
                 defer child_block.instructions.deinit(sema.gpa);
+                // We won't have any merges, but we must ensure this block is properly labeled for
+                // any `.restore_err_ret_index_*` instructions.
+                var label: Block.Label = .{
+                    .zir_block = inst,
+                    .merges = undefined,
+                };
+                child_block.label = &label;
                 child_block.comptime_reason = .{ .reason = .{
                     .src = src,
                     .r = .{ .simple = extra.data.reason },
 @@ -1672,7 +1676,9 @@ fn analyzeBodyInner(
                 const result = try sema.resolveInlineBody(&child_block, block_body, inst);
-                if (!try sema.isComptimeKnown(result)) {
+                // Only check for the result being comptime-known in the outermost `block_comptime`.
+                // That way, AstGen can safely elide redundant `block_comptime` without affecting semantics.
+                if (!block.isComptime() and !try sema.isComptimeKnown(result)) {
                     return sema.failWithNeededComptime(&child_block, src, null);
                 }

test/behavior/eval.zig+7

...	@@ -1744,3 +1744,10 @@ test "block with comptime-known result but possible runtime exit is comptime-kno	...	@@ -1744,3 +1744,10 @@ test "block with comptime-known result but possible runtime exit is comptime-kno
1744	comptime assert(a == 123);	1744	comptime assert(a == 123);
1745	comptime assert(b == 456);	1745	comptime assert(b == 456);
1746	}	1746	}
		1747
		1748	test "comptime labeled block implicit exit" {
		1749	const result = comptime b: {
		1750	if (false) break :b 123;
		1751	};
		1752	comptime assert(result == {});
		1753	}