safety: show error return trace when unwrapping error in switch

ci/azure/pipelines.yml

@@ -16,7 +16,7 @@ jobs:
     vmImage: 'windows-2019'
   variables:
     TARGET: 'x86_64-windows-gnu'
-    ZIG_LLVM_CLANG_LLD_NAME: 'zig+llvm+lld+clang-${{ variables.TARGET }}-0.10.0-dev.61+9be8396b7'
+    ZIG_LLVM_CLANG_LLD_NAME: 'zig+llvm+lld+clang-${{ variables.TARGET }}-0.10.0-dev.4138+3f5ee6f03'
     ZIG_LLVM_CLANG_LLD_URL: 'https://ziglang.org/deps/${{ variables.ZIG_LLVM_CLANG_LLD_NAME }}.zip'
   steps:
   - pwsh: |

lib/c.zig

@@ -58,7 +58,7 @@ comptime {
 
 // Avoid dragging in the runtime safety mechanisms into this .o file,
 // unless we're trying to test this file.
-pub fn panic(msg: []const u8, error_return_trace: ?*std.builtin.StackTrace) noreturn {
+pub fn panic(msg: []const u8, error_return_trace: ?*std.builtin.StackTrace, _: ?usize) noreturn {
     @setCold(true);
     _ = error_return_trace;
     if (builtin.is_test) {

lib/compiler_rt/common.zig

@@ -60,7 +60,7 @@ pub const want_sparc_abi = builtin.cpu.arch.isSPARC();
 
 // Avoid dragging in the runtime safety mechanisms into this .o file,
 // unless we're trying to test compiler-rt.
-pub fn panic(msg: []const u8, error_return_trace: ?*std.builtin.StackTrace) noreturn {
+pub fn panic(msg: []const u8, error_return_trace: ?*std.builtin.StackTrace, _: ?usize) noreturn {
     _ = error_return_trace;
     if (builtin.is_test) {
         @setCold(true);

lib/ssp.zig

@@ -20,7 +20,7 @@ extern fn memcpy(noalias dest: ?[*]u8, noalias src: ?[*]const u8, n: usize) call
 extern fn memmove(dest: ?[*]u8, src: ?[*]const u8, n: usize) callconv(.C) ?[*]u8;
 
 // Avoid dragging in the runtime safety mechanisms into this .o file.
-pub fn panic(msg: []const u8, error_return_trace: ?*std.builtin.StackTrace) noreturn {
+pub fn panic(msg: []const u8, error_return_trace: ?*std.builtin.StackTrace, _: ?usize) noreturn {
     _ = msg;
     _ = error_return_trace;
     @setCold(true);

lib/std/builtin.zig

@@ -748,7 +748,7 @@ const testFnProto = switch (builtin.zig_backend) {
 
 /// This function type is used by the Zig language code generation and
 /// therefore must be kept in sync with the compiler implementation.
-pub const PanicFn = fn ([]const u8, ?*StackTrace) noreturn;
+pub const PanicFn = fn ([]const u8, ?*StackTrace, ?usize) noreturn;
 
 /// This function is used by the Zig language code generation and
 /// therefore must be kept in sync with the compiler implementation.
@@ -761,7 +761,7 @@ else
 
 /// This function is used by the Zig language code generation and
 /// therefore must be kept in sync with the compiler implementation.
-pub fn default_panic(msg: []const u8, error_return_trace: ?*StackTrace) noreturn {
+pub fn default_panic(msg: []const u8, error_return_trace: ?*StackTrace, ret_addr: ?usize) noreturn {
     @setCold(true);
 
     // Until self-hosted catches up with stage1 language features, we have a simpler
@@ -839,7 +839,7 @@ pub fn default_panic(msg: []const u8, error_return_trace: ?*StackTrace) noreturn
             std.os.abort();
         },
         else => {
-            const first_trace_addr = @returnAddress();
+            const first_trace_addr = ret_addr orelse @returnAddress();
             std.debug.panicImpl(error_return_trace, first_trace_addr, msg);
         },
     }
@@ -853,17 +853,17 @@ pub fn checkNonScalarSentinel(expected: anytype, actual: @TypeOf(expected)) void
 
 pub fn panicSentinelMismatch(expected: anytype, actual: @TypeOf(expected)) noreturn {
     @setCold(true);
-    std.debug.panic("sentinel mismatch: expected {any}, found {any}", .{ expected, actual });
+    std.debug.panicExtra(null, @returnAddress(), "sentinel mismatch: expected {any}, found {any}", .{ expected, actual });
 }
 
 pub fn panicUnwrapError(st: ?*StackTrace, err: anyerror) noreturn {
     @setCold(true);
-    std.debug.panicExtra(st, "attempt to unwrap error: {s}", .{@errorName(err)});
+    std.debug.panicExtra(st, @returnAddress(), "attempt to unwrap error: {s}", .{@errorName(err)});
 }
 
 pub fn panicOutOfBounds(index: usize, len: usize) noreturn {
     @setCold(true);
-    std.debug.panic("index out of bounds: index {d}, len {d}", .{ index, len });
+    std.debug.panicExtra(null, @returnAddress(), "index out of bounds: index {d}, len {d}", .{ index, len });
 }
 
 pub noinline fn returnError(st: *StackTrace) void {

lib/std/debug.zig

@@ -284,13 +284,14 @@ pub fn assert(ok: bool) void {
 pub fn panic(comptime format: []const u8, args: anytype) noreturn {
     @setCold(true);
 
-    panicExtra(null, format, args);
+    panicExtra(null, null, format, args);
 }
 
 /// `panicExtra` is useful when you want to print out an `@errorReturnTrace`
 /// and also print out some values.
 pub fn panicExtra(
     trace: ?*std.builtin.StackTrace,
+    ret_addr: ?usize,
     comptime format: []const u8,
     args: anytype,
 ) noreturn {
@@ -308,7 +309,7 @@ pub fn panicExtra(
             break :blk &buf;
         },
     };
-    std.builtin.panic(msg, trace);
+    std.builtin.panic(msg, trace, ret_addr);
 }
 
 /// Non-zero whenever the program triggered a panic.

src/AstGen.zig

@@ -884,33 +884,6 @@ fn expr(gz: *GenZir, scope: *Scope, rl: ResultLoc, node: Ast.Node.Index) InnerEr
                 catch_token + 2
             else
                 null;
-
-            var rhs = node_datas[node].rhs;
-            while (true) switch (node_tags[rhs]) {
-                .grouped_expression => rhs = node_datas[rhs].lhs,
-                .unreachable_literal => {
-                    if (payload_token != null and mem.eql(u8, tree.tokenSlice(payload_token.?), "_")) {
-                        return astgen.failTok(payload_token.?, "discard of error capture; omit it instead", .{});
-                    } else if (payload_token != null) {
-                        return astgen.failTok(payload_token.?, "unused capture", .{});
-                    }
-                    const lhs = node_datas[node].lhs;
-
-                    const operand = try reachableExpr(gz, scope, switch (rl) {
-                        .ref => .ref,
-                        else => .none,
-                    }, lhs, lhs);
-                    const result = try gz.addUnNode(switch (rl) {
-                        .ref => .err_union_payload_safe_ptr,
-                        else => .err_union_payload_safe,
-                    }, operand, node);
-                    switch (rl) {
-                        .none, .coerced_ty, .discard, .ref => return result,
-                        else => return rvalue(gz, rl, result, lhs),
-                    }
-                },
-                else => break,
-            };
             switch (rl) {
                 .ref => return orelseCatchExpr(
                     gz,
@@ -2375,9 +2348,7 @@ fn addEnsureResult(gz: *GenZir, maybe_unused_result: Zir.Inst.Ref, statement: As
             .optional_payload_unsafe,
             .optional_payload_safe_ptr,
             .optional_payload_unsafe_ptr,
-            .err_union_payload_safe,
             .err_union_payload_unsafe,
-            .err_union_payload_safe_ptr,
             .err_union_payload_unsafe_ptr,
             .err_union_code,
             .err_union_code_ptr,