From e323cf1264f390911dcc2efea71d46be1d631d92 Mon Sep 17 00:00:00 2001
From: Veikka Tuominen <git@vexu.eu>
Date: Sat, 27 Aug 2022 18:48:01 +0300
Subject: stage2: change how defers are stored in Zir

Storing defers this way has the benefits that the defer doesn't get
analyzed multiple times in AstGen, it takes up less space, and it
makes Sema aware of defers allowing for 'unreachable else prong'
error on error sets in generic code.

The disadvantage is that it is a bit more complex and errdefers with
payloads now emit a placeholder instruction (but those are rare).

Sema.zig before:
  Total ZIR bytes:    3.7794370651245117MiB
  Instructions:       238996 (2.051319122314453MiB)
  String Table Bytes: 89.2802734375KiB
  Extra Data Items:   430144 (1.640869140625MiB)
Sema.zig after:
  Total ZIR bytes:    3.3344192504882812MiB
  Instructions:       211829 (1.8181428909301758MiB)
  String Table Bytes: 89.2802734375KiB
  Extra Data Items:   374611 (1.4290275573730469MiB)
---
 .../return_from_defer_expression.zig               |  1 +
 .../uncreachable_else_prong_err_set.zig            | 25 ++++++++++++++++++++++
 2 files changed, 26 insertions(+)
 create mode 100644 test/cases/compile_errors/uncreachable_else_prong_err_set.zig

(limited to 'test/cases/compile_errors')

diff --git a/test/cases/compile_errors/return_from_defer_expression.zig b/test/cases/compile_errors/return_from_defer_expression.zig
index e60b8ae848..12aa08a11c 100644
--- a/test/cases/compile_errors/return_from_defer_expression.zig
+++ b/test/cases/compile_errors/return_from_defer_expression.zig
@@ -19,3 +19,4 @@ export fn entry() usize { return @sizeOf(@TypeOf(testTrickyDefer)); }
 // target=native
 //
 // :4:11: error: 'try' not allowed inside defer expression
+// :4:5: note: defer expression here
diff --git a/test/cases/compile_errors/uncreachable_else_prong_err_set.zig b/test/cases/compile_errors/uncreachable_else_prong_err_set.zig
new file mode 100644
index 0000000000..4b0ae462d6
--- /dev/null
+++ b/test/cases/compile_errors/uncreachable_else_prong_err_set.zig
@@ -0,0 +1,25 @@
+pub export fn complex() void {
+    var a: error{ Foo, Bar } = error.Foo;
+    switch (a) {
+        error.Foo => unreachable,
+        error.Bar => unreachable,
+        else => {
+            @compileError("<something complex here>");
+        },
+    }
+}
+
+pub export fn simple() void {
+    var a: error{ Foo, Bar } = error.Foo;
+    switch (a) {
+        error.Foo => unreachable,
+        error.Bar => unreachable,
+        else => |e| return e,
+    }
+}
+
+// error
+// backend=llvm
+// target=native
+//
+// :6:14: error: unreachable else prong; all cases already handled
-- 
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