stage2: fix incremental compilation handling of parse errors

Before, incremental compilation would crash when trying to emit compile
errors for the update after introducing a parse error.

Parse errors are handled by not invalidating any existing semantic
analysis. However, only the parse error must be reported, with all the
other errors suppressed. Once the parse error is fixed, the new file can
be treated as an update to the previously-succeeded update.

1 files changed, 14 insertions, 5 deletions

diff --git a/src/Module.zig b/src/Module.zig
index 98dad994bd..ccf6996cae 100644
--- a/src/Module.zig
+++ b/src/Module.zig
@@ -65,8 +65,8 @@ emit_h_failed_decls: std.AutoArrayHashMapUnmanaged(*Decl, *ErrorMsg) = .{},
 /// Keep track of one `@compileLog` callsite per owner Decl.
 compile_log_decls: std.AutoArrayHashMapUnmanaged(*Decl, SrcLoc) = .{},
 /// Using a map here for consistency with the other fields here.
-/// The ErrorMsg memory is owned by the `Scope`, using Module's general purpose allocator.
-failed_files: std.AutoArrayHashMapUnmanaged(*Scope, *ErrorMsg) = .{},
+/// The ErrorMsg memory is owned by the `Scope.File`, using Module's general purpose allocator.
+failed_files: std.AutoArrayHashMapUnmanaged(*Scope.File, *ErrorMsg) = .{},
 /// Using a map here for consistency with the other fields here.
 /// The ErrorMsg memory is owned by the `Export`, using Module's general purpose allocator.
 failed_exports: std.AutoArrayHashMapUnmanaged(*Export, *ErrorMsg) = .{},
@@ -732,10 +732,12 @@ pub const Scope = struct {
 
         pub fn unload(file: *File, gpa: *Allocator) void {
             switch (file.status) {
-                .never_loaded,
                 .unloaded_parse_failure,
+                .never_loaded,
                 .unloaded_success,
-                => {},
+                => {
+                    file.status = .unloaded_success;
+                },
 
                 .loaded_success => {
                     file.tree.deinit(gpa);
@@ -3241,7 +3243,7 @@ pub fn getAstTree(mod: *Module, root_scope: *Scope.File) !*const ast.Tree {
                     .msg = msg.toOwnedSlice(),
                 };
 
-                mod.failed_files.putAssumeCapacityNoClobber(&root_scope.base, err_msg);
+                mod.failed_files.putAssumeCapacityNoClobber(root_scope, err_msg);
                 root_scope.status = .unloaded_parse_failure;
                 return error.AnalysisFail;
             }
@@ -4691,3 +4693,10 @@ pub fn parseStrLit(
         },
     }
 }
+
+pub fn unloadFile(mod: *Module, file_scope: *Scope.File) void {
+    if (file_scope.status == .unloaded_parse_failure) {
+        mod.failed_files.swapRemove(file_scope).?.value.destroy(mod.gpa);
+    }
+    file_scope.unload(mod.gpa);
+}