stage2: omit Decl compile errors from failed AstGen files

Just like when new parse errors occur during an update, when new AstGen
errors occur during an update, we do not reveal compile errors for Decl
objects which are inside of a newly failed File. Once the File passes
AstGen successfully, it will be compared with the previously succeeded
ZIR and the saved Decl compile errors will be handled properly.

src/Compilation.zig

@@ -1696,17 +1696,15 @@ pub fn totalErrorCount(self: *Compilation) usize {
         // the previous parse success, including compile errors, but we cannot
         // emit them until the file succeeds parsing.
         for (module.failed_decls.items()) |entry| {
-            if (entry.key.namespace.file_scope.status == .parse_failure) {
+            if (entry.key.namespace.file_scope.okToReportErrors()) {
-                continue;
+                total += 1;
             }
-            total += 1;
         }
         if (module.emit_h) |emit_h| {
             for (emit_h.failed_decls.items()) |entry| {
-                if (entry.key.namespace.file_scope.status == .parse_failure) {
+                if (entry.key.namespace.file_scope.okToReportErrors()) {
-                    continue;
+                    total += 1;
                 }
-                total += 1;
             }
         }
     }
@@ -1767,21 +1765,19 @@ pub fn getAllErrorsAlloc(self: *Compilation) !AllErrors {
             }
         }
         for (module.failed_decls.items()) |entry| {
-            if (entry.key.namespace.file_scope.status == .parse_failure) {
+            // Skip errors for Decls within files that had a parse failure.
-                // Skip errors for Decls within files that had a parse failure.
+            // We'll try again once parsing succeeds.
-                // We'll try again once parsing succeeds.
+            if (entry.key.namespace.file_scope.okToReportErrors()) {
-                continue;
+                try AllErrors.add(module, &arena, &errors, entry.value.*);
             }
-            try AllErrors.add(module, &arena, &errors, entry.value.*);
         }
         if (module.emit_h) |emit_h| {
             for (emit_h.failed_decls.items()) |entry| {
-                if (entry.key.namespace.file_scope.status == .parse_failure) {
+                // Skip errors for Decls within files that had a parse failure.
-                    // Skip errors for Decls within files that had a parse failure.
+                // We'll try again once parsing succeeds.
-                    // We'll try again once parsing succeeds.
+                if (entry.key.namespace.file_scope.okToReportErrors()) {
-                    continue;
+                    try AllErrors.add(module, &arena, &errors, entry.value.*);
                 }
-                try AllErrors.add(module, &arena, &errors, entry.value.*);
             }
         }
         for (module.failed_exports.items()) |entry| {

src/Module.zig

@@ -1138,6 +1138,13 @@ pub const Scope = struct {
             const loc = std.zig.findLineColumn(file.source.bytes, src);
             std.debug.print("{s}:{d}:{d}\n", .{ file.sub_file_path, loc.line + 1, loc.column + 1 });
         }
+
+        pub fn okToReportErrors(file: File) bool {
+            return switch (file.status) {
+                .parse_failure, .astgen_failure => false,
+                else => true,
+            };
+        }
     };
 
     /// This is the context needed to semantically analyze ZIR instructions and

test/stage2/test.zig

@@ -1225,7 +1225,7 @@ pub fn addCases(ctx: *TestContext) !void {
     {
         var case = ctx.obj("variable shadowing", linux_x64);
         case.addError(
-            \\pub export fn _start() noreturn {
+            \\export fn _start() noreturn {
             \\    var i: u32 = 10;
             \\    var i: u32 = 10;
             \\    unreachable;
@@ -1251,7 +1251,7 @@ pub fn addCases(ctx: *TestContext) !void {
         var case = ctx.obj("@compileLog", linux_x64);
         // The other compile error prevents emission of a "found compile log" statement.
         case.addError(
-            \\pub export fn _start() noreturn {
+            \\export fn _start() noreturn {
             \\    const b = true;
             \\    var f: u32 = 1;
             \\    @compileLog(b, 20, f, x);
@@ -1293,10 +1293,9 @@ pub fn addCases(ctx: *TestContext) !void {
             \\    _ = foo;
             \\}
             \\extern var foo: i32;
-            \\pub export fn _start() void {}
         , &[_][]const u8{":2:9: error: unable to resolve comptime value"});
         case.addError(
-            \\pub export fn _start() void {
+            \\export fn entry() void {
             \\    _ = foo;
             \\}
             \\extern var foo;