Audit usages of toOwnedSlice (#32001)

Followup to #30769

I grepped for `try .*toOwnedSlice` and checked all of them by hand.

Fixes a bunch of memory leaks removes usages or `errdefer` and `vars` in some places. I also switched array_list.Managed to ArrayList where it was convenient.

Reviewed-on: https://codeberg.org/ziglang/zig/pulls/32001
Reviewed-by: Andrew Kelley <andrew@ziglang.org>

src/codegen/aarch64.zig

@@ -170,26 +170,27 @@ pub fn generate(
     const prologue = isel.instructions.items.len;
     const epilogue = try isel.layout(param_it, is_sysv_var_args, saved_gra_len, saved_vra_len, mod);
 
-    const instructions = try isel.instructions.toOwnedSlice(gpa);
-    var mir: Mir = .{
+    try isel.instructions.shrinkToLen(gpa);
+    try isel.literals.shrinkToLen(gpa);
+    try isel.nav_relocs.shrinkToLen(gpa);
+    try isel.uav_relocs.shrinkToLen(gpa);
+    try isel.lazy_relocs.shrinkToLen(gpa);
+    try isel.global_relocs.shrinkToLen(gpa);
+    try isel.literal_relocs.shrinkToLen(gpa);
+
+    const instructions = isel.instructions.toOwnedSliceAssert();
+
+    return .{
         .prologue = instructions[prologue..epilogue],
         .body = instructions[0..prologue],
         .epilogue = instructions[epilogue..],
-        .literals = &.{},
-        .nav_relocs = &.{},
-        .uav_relocs = &.{},
-        .lazy_relocs = &.{},
-        .global_relocs = &.{},
-        .literal_relocs = &.{},
+        .literals = isel.literals.toOwnedSliceAssert(),
+        .nav_relocs = isel.nav_relocs.toOwnedSliceAssert(),
+        .uav_relocs = isel.uav_relocs.toOwnedSliceAssert(),
+        .lazy_relocs = isel.lazy_relocs.toOwnedSliceAssert(),
+        .global_relocs = isel.global_relocs.toOwnedSliceAssert(),
+        .literal_relocs = isel.literal_relocs.toOwnedSliceAssert(),
     };
-    errdefer mir.deinit(gpa);
-    mir.literals = try isel.literals.toOwnedSlice(gpa);
-    mir.nav_relocs = try isel.nav_relocs.toOwnedSlice(gpa);
-    mir.uav_relocs = try isel.uav_relocs.toOwnedSlice(gpa);
-    mir.lazy_relocs = try isel.lazy_relocs.toOwnedSlice(gpa);
-    mir.global_relocs = try isel.global_relocs.toOwnedSlice(gpa);
-    mir.literal_relocs = try isel.literal_relocs.toOwnedSlice(gpa);
-    return mir;
 }
 
 test {

src/codegen/sparc64/CodeGen.zig

@@ -324,13 +324,12 @@ pub fn generate(
         else => |e| return e,
     };
 
-    var mir: Mir = .{
+    try function.mir_extra.shrinkToLen(gpa);
+
+    return .{
         .instructions = function.mir_instructions.toOwnedSlice(),
-        .extra = &.{}, // fallible, so populated after errdefer
+        .extra = function.mir_extra.toOwnedSliceAssert(),
     };
-    errdefer mir.deinit(gpa);
-    mir.extra = try function.mir_extra.toOwnedSlice(gpa);
-    return mir;
 }
 
 fn gen(self: *Self) !void {

src/codegen/wasm/CodeGen.zig

@@ -852,10 +852,13 @@ fn generateInner(cg: *CodeGen, any_returns: bool) InnerError!Mir {
     try cg.addTag(.end);
     try cg.addTag(.dbg_epilogue_begin);
 
-    var mir: Mir = .{
+    try cg.mir_extra.shrinkToLen(cg.gpa);
+    try cg.mir_locals.shrinkToLen(cg.gpa);
+
+    return .{
         .instructions = cg.mir_instructions.toOwnedSlice(),
-        .extra = &.{}, // fallible so assigned after errdefer
-        .locals = &.{}, // fallible so assigned after errdefer
+        .extra = cg.mir_extra.toOwnedSliceAssert(),
+        .locals = cg.mir_locals.toOwnedSliceAssert(),
         .prologue = if (cg.initial_stack_value == .none) .none else .{
             .sp_local = cg.initial_stack_value.local.value,
             .flags = .{ .stack_alignment = cg.stack_alignment },
@@ -867,10 +870,6 @@ fn generateInner(cg: *CodeGen, any_returns: bool) InnerError!Mir {
         .func_tys = cg.mir_func_tys.move(),
         .error_name_table_ref_count = cg.error_name_table_ref_count,
     };
-    errdefer mir.deinit(cg.gpa);
-    mir.extra = try cg.mir_extra.toOwnedSlice(cg.gpa);
-    mir.locals = try cg.mir_locals.toOwnedSlice(cg.gpa);
-    return mir;
 }
 
 const CallWValues = struct {

src/codegen/x86_64/CodeGen.zig

@@ -998,22 +998,19 @@ pub fn generate(
         } },
     });
 
-    var mir: Mir = .{
-        .instructions = .empty,
-        .extra = &.{},
-        .string_bytes = &.{},
-        .locals = &.{},
-        .table = &.{},
-        .frame_locs = .empty,
+    try function.mir_extra.shrinkToLen(gpa);
+    try function.mir_string_bytes.shrinkToLen(gpa);
+    try function.mir_locals.shrinkToLen(gpa);
+    try function.mir_table.shrinkToLen(gpa);
+
+    return .{
+        .instructions = function.mir_instructions.toOwnedSlice(),
+        .extra = function.mir_extra.toOwnedSliceAssert(),
+        .string_bytes = function.mir_string_bytes.toOwnedSliceAssert(),
+        .locals = function.mir_locals.toOwnedSliceAssert(),
+        .table = function.mir_table.toOwnedSliceAssert(),
+        .frame_locs = function.frame_locs.toOwnedSlice(),
     };
-    errdefer mir.deinit(gpa);
-    mir.instructions = function.mir_instructions.toOwnedSlice();
-    mir.extra = try function.mir_extra.toOwnedSlice(gpa);
-    mir.string_bytes = try function.mir_string_bytes.toOwnedSlice(gpa);
-    mir.locals = try function.mir_locals.toOwnedSlice(gpa);
-    mir.table = try function.mir_table.toOwnedSlice(gpa);
-    mir.frame_locs = function.frame_locs.toOwnedSlice();
-    return mir;
 }
 
 pub fn getTmpMir(cg: *CodeGen) Mir {