From dd66e0addb30d795a04324096c913ca89ccbcf40 Mon Sep 17 00:00:00 2001
From: Jacob Young <jacobly0@users.noreply.github.com>
Date: Mon, 27 Mar 2023 06:55:48 -0400
Subject: [PATCH] Sema: fix empty slice pointer value

We just checked that inst_child_ty was effectively a zero-bit type, so
it is certainly not the non-zero alignment we are looking for.

Closes #15085
---
 src/Sema.zig            |  7 ++++++-
 src/codegen/c.zig       |  2 +-
 src/codegen/llvm.zig    |  2 +-
 test/behavior/slice.zig | 16 ++++++++++++----
 4 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/src/Sema.zig b/src/Sema.zig
index 13327657a8..1f375853cb 100644
--- a/src/Sema.zig
+++ b/src/Sema.zig
@@ -25152,7 +25152,7 @@ fn coerceExtra(
                             .ptr = if (dest_info.@"align" != 0)
                                 try Value.Tag.int_u64.create(sema.arena, dest_info.@"align")
                             else
-                                try inst_child_ty.lazyAbiAlignment(target, sema.arena),
+                                try dest_info.pointee_type.lazyAbiAlignment(target, sema.arena),
                             .len = Value.zero,
                         });
                         return sema.addConstant(dest_ty, slice_val);
@@ -30213,6 +30213,11 @@ fn resolveLazyValue(sema: *Sema, val: Value) CompileError!void {
                 try sema.resolveLazyValue(elem_val);
             }
         },
+        .slice => {
+            const slice = val.castTag(.slice).?.data;
+            try sema.resolveLazyValue(slice.ptr);
+            return sema.resolveLazyValue(slice.len);
+        },
         else => return,
     }
 }
diff --git a/src/codegen/c.zig b/src/codegen/c.zig
index 0c85f0f923..6c4bb3c688 100644
--- a/src/codegen/c.zig
+++ b/src/codegen/c.zig
@@ -1069,7 +1069,7 @@ pub const DeclGen = struct {
                     const extern_fn = val.castTag(.extern_fn).?.data;
                     try dg.renderDeclName(writer, extern_fn.owner_decl, 0);
                 },
-                .int_u64, .one => {
+                .int_u64, .one, .int_big_positive, .lazy_align, .lazy_size => {
                     try writer.writeAll("((");
                     try dg.renderType(writer, ty);
                     return writer.print("){x})", .{try dg.fmtIntLiteral(Type.usize, val, .Other)});
diff --git a/src/codegen/llvm.zig b/src/codegen/llvm.zig
index dd13087afe..4b28fe2afe 100644
--- a/src/codegen/llvm.zig
+++ b/src/codegen/llvm.zig
@@ -3397,7 +3397,7 @@ pub const DeclGen = struct {
                     };
                     return dg.context.constStruct(&fields, fields.len, .False);
                 },
-                .int_u64, .one, .int_big_positive => {
+                .int_u64, .one, .int_big_positive, .lazy_align, .lazy_size => {
                     const llvm_usize = try dg.lowerType(Type.usize);
                     const llvm_int = llvm_usize.constInt(tv.val.toUnsignedInt(target), .False);
                     return llvm_int.constIntToPtr(try dg.lowerType(tv.ty));
diff --git a/test/behavior/slice.zig b/test/behavior/slice.zig
index 029f6838d0..a9aa9e50e1 100644
--- a/test/behavior/slice.zig
+++ b/test/behavior/slice.zig
@@ -723,10 +723,18 @@ test "slice with dereferenced value" {
 test "empty slice ptr is non null" {
     if (builtin.zig_backend == .stage2_aarch64 and builtin.os.tag == .macos) return error.SkipZigTest; // TODO
 
-    const empty_slice: []u8 = &[_]u8{};
-    const p: [*]u8 = empty_slice.ptr + 0;
-    const t = @ptrCast([*]i8, p);
-    try expect(@ptrToInt(t) == @ptrToInt(empty_slice.ptr));
+    {
+        const empty_slice: []u8 = &[_]u8{};
+        const p: [*]u8 = empty_slice.ptr + 0;
+        const t = @ptrCast([*]i8, p);
+        try expect(@ptrToInt(t) == @ptrToInt(empty_slice.ptr));
+    }
+    {
+        const empty_slice: []u8 = &.{};
+        const p: [*]u8 = empty_slice.ptr + 0;
+        const t = @ptrCast([*]i8, p);
+        try expect(@ptrToInt(t) == @ptrToInt(empty_slice.ptr));
+    }
 }
 
 test "slice decays to many pointer" {