Revert "AstGen: preserve inferred ptr result loc for breaks"

This reverts commit 8bf3e1f, which
introduced miscompilations for peer expressions any time they needed
coercions to runtime types.

I opened #11957 as a proposal to accomplish the goal of the reverted
commit.

Closes #11898

src/AstGen.zig

@@ -10007,7 +10007,7 @@ const GenZir = struct {
             .inferred_ptr => |ptr| {
                 gz.rl_ty_inst = .none;
                 gz.rl_ptr = ptr;
-                gz.break_result_loc = parent_rl;
+                gz.break_result_loc = .{ .block_ptr = gz };
             },
 
             .block_ptr => |parent_block_scope| {

src/Sema.zig

@@ -3079,28 +3079,6 @@ fn zirResolveInferredAlloc(sema: *Sema, block: *Block, inst: Zir.Inst.Index) Com
 
             if (var_is_mut) {
                 try sema.validateVarType(block, ty_src, final_elem_ty, false);
-
-                // The value might have been bitcasted into a comptime only
-                // pointer type such as `*@Type(.EnumLiteral)` so we must now
-                // update all the stores to not give backends invalid AIR.
-
-                var air_tags = sema.air_instructions.items(.tag);
-                var air_data = sema.air_instructions.items(.data);
-                var peer_inst_index: usize = 0;
-                var i = ptr_inst;
-                while (i < air_tags.len and peer_inst_index < peer_inst_list.len) : (i += 1) {
-                    if (air_tags[i] != .store) continue;
-                    if (air_data[i].bin_op.rhs == peer_inst_list[peer_inst_index]) {
-                        peer_inst_index += 1;
-                        _ = (try sema.resolveMaybeUndefVal(block, .unneeded, air_data[i].bin_op.rhs)) orelse continue;
-                        const coerced_val = try sema.coerce(block, final_elem_ty, air_data[i].bin_op.rhs, .unneeded);
-                        air_tags = sema.air_instructions.items(.tag);
-                        air_data = sema.air_instructions.items(.data);
-
-                        air_data[i].bin_op.lhs = ptr;
-                        air_data[i].bin_op.rhs = coerced_val;
-                    }
-                }
             } else ct: {
                 // Detect if the value is comptime known. In such case, the
                 // last 3 AIR instructions of the block will look like this:

test/behavior/basic.zig

@@ -928,18 +928,6 @@ test "try in labeled block doesn't cast to wrong type" {
     _ = s;
 }
 
-test "comptime int in switch in catch is casted to correct inferred type" {
-    if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
-    if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
-
-    var a: error{ A, B }!u64 = 0;
-    var b = a catch |err| switch (err) {
-        error.A => 0,
-        else => unreachable,
-    };
-    _ = b;
-}
-
 test "vector initialized with array init syntax has proper type" {
     comptime {
         const actual = -@Vector(4, i32){ 1, 2, 3, 4 };

test/behavior/cast.zig

@@ -812,6 +812,7 @@ test "peer type resolution: error union after non-error" {
 }
 
 test "peer cast *[0]T to E![]const T" {
+    if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
     if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
     if (builtin.zig_backend == .stage2_c) return error.SkipZigTest; // TODO
     if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest; // TODO
@@ -826,6 +827,7 @@ test "peer cast *[0]T to E![]const T" {
 }
 
 test "peer cast *[0]T to []const T" {
+    if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
     if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
     if (builtin.zig_backend == .stage2_c) return error.SkipZigTest; // TODO
     if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest; // TODO

test/behavior/error.zig

@@ -709,7 +709,7 @@ test "simple else prong allowed even when all errors handled" {
         }
     };
     var value = S.foo() catch |err| switch (err) {
-        error.Foo => 255,
+        error.Foo => @as(u8, 255),
         else => |e| return e,
     };
     try expect(value == 255);

test/behavior/if.zig

@@ -111,3 +111,20 @@ test "if prongs cast to expected type instead of peer type resolution" {
     try S.doTheTest(false);
     comptime try S.doTheTest(false);
 }
+
+test "if peer expressions inferred optional type" {
+    if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest;
+    if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
+    if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
+
+    var self: []const u8 = "abcdef";
+    var index: usize = 0;
+    var left_index = (index << 1) + 1;
+    var right_index = left_index + 1;
+    var left = if (left_index < self.len) self[left_index] else null;
+    var right = if (right_index < self.len) self[right_index] else null;
+    try expect(left_index < self.len);
+    try expect(right_index < self.len);
+    try expect(left.? == 98);
+    try expect(right.? == 99);
+}