sema: load the correct AST in failWithInvalidComptimeFieldStore

The container we want to get the fields from might not be declared in the
same file as the block we are analyzing, so we should get the AST from
the decl's file instead.

src/Sema.zig

@@ -1868,9 +1868,11 @@ fn failWithInvalidComptimeFieldStore(sema: *Sema, block: *Block, init_src: LazyS
         errdefer msg.destroy(sema.gpa);
 
         const decl_index = container_ty.getOwnerDeclOrNull() orelse break :msg msg;
-
-        const tree = try sema.getAstTree(block);
         const decl = sema.mod.declPtr(decl_index);
+        const tree = decl.getFileScope().getTree(sema.gpa) catch |err| {
+            log.err("unable to load AST to report compile error: {s}", .{@errorName(err)});
+            return error.AnalysisFail;
+        };
         const field_src = enumFieldSrcLoc(decl, tree.*, 0, field_index);
         const default_value_src: LazySrcLoc = .{ .node_offset_field_default = field_src.node_offset.x };
 

test/compile_errors.zig

@@ -225,6 +225,32 @@ pub fn addCases(ctx: *TestContext) !void {
         });
     }
 
+    {
+        const case = ctx.obj("invalid store to comptime field", .{});
+        case.backend = .stage2;
+
+        case.addSourceFile("a.zig",
+            \\pub const S = struct {
+            \\    comptime foo: u32 = 1,
+            \\    bar: u32,
+            \\    pub fn foo(x: @This()) void {
+            \\        _ = x;
+            \\    }
+            \\};
+        );
+
+        case.addError(
+            \\const a = @import("a.zig");
+            \\
+            \\export fn entry() void {
+            \\    _ = a.S.foo(a.S{ .foo = 2, .bar = 2 });
+            \\}
+        , &[_][]const u8{
+            ":4:23: error: value stored in comptime field does not match the default value of the field",
+            ":2:25: note: default value set here",
+        });
+    }
+
     // TODO test this in stage2, but we won't even try in stage1
     //ctx.objErrStage1("inline fn calls itself indirectly",
     //    \\export fn foo() void {