Zcu: store `LazySrcLoc` in error messages

This change modifies `Zcu.ErrorMsg` to store a `Zcu.LazySrcLoc` rather
than a `Zcu.SrcLoc`. Everything else is dominoes.

The reason for this change is incremental compilation. If a failed
`AnalUnit` is up-to-date on an update, we want to re-use the old error
messages. However, the file containing the error location may have been
modified, and `SrcLoc` cannot survive such a modification. `LazySrcLoc`
is designed to be correct across incremental updates. Therefore, we
defer source location resolution until `Compilation` gathers the compile
errors into the `ErrorBundle`.

8 files changed, 45 insertions, 73 deletions

diff --git a/src/link/Coff.zig b/src/link/Coff.zig
index 94b9ca520e..366ba87509 100644
--- a/src/link/Coff.zig
+++ b/src/link/Coff.zig
@@ -1144,7 +1144,7 @@ pub fn updateFunc(self: *Coff, mod: *Module, func_index: InternPool.Index, air:
 
     const res = try codegen.generateFunction(
         &self.base,
-        decl.navSrcLoc(mod).upgrade(mod),
+        decl.navSrcLoc(mod),
         func_index,
         air,
         liveness,
@@ -1179,7 +1179,7 @@ pub fn lowerUnnamedConst(self: *Coff, val: Value, decl_index: InternPool.DeclInd
     const sym_name = try std.fmt.allocPrint(gpa, "__unnamed_{}_{d}", .{ decl_name.fmt(&mod.intern_pool), index });
     defer gpa.free(sym_name);
     const ty = val.typeOf(mod);
-    const atom_index = switch (try self.lowerConst(sym_name, val, ty.abiAlignment(mod), self.rdata_section_index.?, decl.navSrcLoc(mod).upgrade(mod))) {
+    const atom_index = switch (try self.lowerConst(sym_name, val, ty.abiAlignment(mod), self.rdata_section_index.?, decl.navSrcLoc(mod))) {
         .ok => |atom_index| atom_index,
         .fail => |em| {
             decl.analysis = .codegen_failure;
@@ -1197,7 +1197,7 @@ const LowerConstResult = union(enum) {
     fail: *Module.ErrorMsg,
 };
 
-fn lowerConst(self: *Coff, name: []const u8, val: Value, required_alignment: InternPool.Alignment, sect_id: u16, src_loc: Module.SrcLoc) !LowerConstResult {
+fn lowerConst(self: *Coff, name: []const u8, val: Value, required_alignment: InternPool.Alignment, sect_id: u16, src_loc: Module.LazySrcLoc) !LowerConstResult {
     const gpa = self.base.comp.gpa;
 
     var code_buffer = std.ArrayList(u8).init(gpa);
@@ -1270,7 +1270,7 @@ pub fn updateDecl(
     defer code_buffer.deinit();
 
     const decl_val = if (decl.val.getVariable(mod)) |variable| Value.fromInterned(variable.init) else decl.val;
-    const res = try codegen.generateSymbol(&self.base, decl.navSrcLoc(mod).upgrade(mod), decl_val, &code_buffer, .none, .{
+    const res = try codegen.generateSymbol(&self.base, decl.navSrcLoc(mod), decl_val, &code_buffer, .none, .{
         .parent_atom_index = atom.getSymbolIndex().?,
     });
     const code = switch (res) {
@@ -1309,14 +1309,7 @@ fn updateLazySymbolAtom(
     const atom = self.getAtomPtr(atom_index);
     const local_sym_index = atom.getSymbolIndex().?;
 
-    const src = if (sym.ty.srcLocOrNull(mod)) |src|
-        src.upgrade(mod)
-    else
-        Module.SrcLoc{
-            .file_scope = undefined,
-            .base_node = undefined,
-            .lazy = .unneeded,
-        };
+    const src = sym.ty.srcLocOrNull(mod) orelse Module.LazySrcLoc.unneeded;
     const res = try codegen.generateLazySymbol(
         &self.base,
         src,
@@ -1560,7 +1553,7 @@ pub fn updateExports(
         },
         .value => |value| self.anon_decls.getPtr(value) orelse blk: {
             const first_exp = mod.all_exports.items[export_indices[0]];
-            const res = try self.lowerAnonDecl(value, .none, first_exp.getSrcLoc(mod));
+            const res = try self.lowerAnonDecl(value, .none, first_exp.src);
             switch (res) {
                 .ok => {},
                 .fail => |em| {
@@ -1585,7 +1578,7 @@ pub fn updateExports(
             if (!mem.eql(u8, section_name, ".text")) {
                 try mod.failed_exports.putNoClobber(gpa, export_idx, try Module.ErrorMsg.create(
                     gpa,
-                    exp.getSrcLoc(mod),
+                    exp.src,
                     "Unimplemented: ExportOptions.section",
                     .{},
                 ));
@@ -1596,7 +1589,7 @@ pub fn updateExports(
         if (exp.opts.linkage == .link_once) {
             try mod.failed_exports.putNoClobber(gpa, export_idx, try Module.ErrorMsg.create(
                 gpa,
-                exp.getSrcLoc(mod),
+                exp.src,
                 "Unimplemented: GlobalLinkage.link_once",
                 .{},
             ));
@@ -1867,7 +1860,7 @@ pub fn lowerAnonDecl(
     self: *Coff,
     decl_val: InternPool.Index,
     explicit_alignment: InternPool.Alignment,
-    src_loc: Module.SrcLoc,
+    src_loc: Module.LazySrcLoc,
 ) !codegen.Result {
     const gpa = self.base.comp.gpa;
     const mod = self.base.comp.module.?;
diff --git a/src/link/Elf.zig b/src/link/Elf.zig
index df8e6c0dd8..c1df153083 100644
--- a/src/link/Elf.zig
+++ b/src/link/Elf.zig
@@ -552,7 +552,7 @@ pub fn lowerAnonDecl(
     self: *Elf,
     decl_val: InternPool.Index,
     explicit_alignment: InternPool.Alignment,
-    src_loc: Module.SrcLoc,
+    src_loc: Module.LazySrcLoc,
 ) !codegen.Result {
     return self.zigObjectPtr().?.lowerAnonDecl(self, decl_val, explicit_alignment, src_loc);
 }
diff --git a/src/link/Elf/ZigObject.zig b/src/link/Elf/ZigObject.zig
index 74e2039f37..57fa610019 100644
--- a/src/link/Elf/ZigObject.zig
+++ b/src/link/Elf/ZigObject.zig
@@ -686,7 +686,7 @@ pub fn lowerAnonDecl(
     elf_file: *Elf,
     decl_val: InternPool.Index,
     explicit_alignment: InternPool.Alignment,
-    src_loc: Module.SrcLoc,
+    src_loc: Module.LazySrcLoc,
 ) !codegen.Result {
     const gpa = elf_file.base.comp.gpa;
     const mod = elf_file.base.comp.module.?;
@@ -1074,7 +1074,7 @@ pub fn updateFunc(
     const res = if (decl_state) |*ds|
         try codegen.generateFunction(
             &elf_file.base,
-            decl.navSrcLoc(mod).upgrade(mod),
+            decl.navSrcLoc(mod),
             func_index,
             air,
             liveness,
@@ -1084,7 +1084,7 @@ pub fn updateFunc(
     else
         try codegen.generateFunction(
             &elf_file.base,
-            decl.navSrcLoc(mod).upgrade(mod),
+            decl.navSrcLoc(mod),
             func_index,
             air,
             liveness,
@@ -1156,13 +1156,13 @@ pub fn updateDecl(
     // TODO implement .debug_info for global variables
     const decl_val = if (decl.val.getVariable(mod)) |variable| Value.fromInterned(variable.init) else decl.val;
     const res = if (decl_state) |*ds|
-        try codegen.generateSymbol(&elf_file.base, decl.navSrcLoc(mod).upgrade(mod), decl_val, &code_buffer, .{
+        try codegen.generateSymbol(&elf_file.base, decl.navSrcLoc(mod), decl_val, &code_buffer, .{
             .dwarf = ds,
         }, .{
             .parent_atom_index = sym_index,
         })
     else
-        try codegen.generateSymbol(&elf_file.base, decl.navSrcLoc(mod).upgrade(mod), decl_val, &code_buffer, .none, .{
+        try codegen.generateSymbol(&elf_file.base, decl.navSrcLoc(mod), decl_val, &code_buffer, .none, .{
             .parent_atom_index = sym_index,
         });
 
@@ -1217,14 +1217,7 @@ fn updateLazySymbol(
         break :blk try self.strtab.insert(gpa, name);
     };
 
-    const src = if (sym.ty.srcLocOrNull(mod)) |src|
-        src.upgrade(mod)
-    else
-        Module.SrcLoc{
-            .file_scope = undefined,
-            .base_node = undefined,
-            .lazy = .unneeded,
-        };
+    const src = sym.ty.srcLocOrNull(mod) orelse Module.LazySrcLoc.unneeded;
     const res = try codegen.generateLazySymbol(
         &elf_file.base,
         src,
@@ -1302,7 +1295,7 @@ pub fn lowerUnnamedConst(
         val,
         ty.abiAlignment(mod),
         elf_file.zig_data_rel_ro_section_index.?,
-        decl.navSrcLoc(mod).upgrade(mod),
+        decl.navSrcLoc(mod),
     )) {
         .ok => |sym_index| sym_index,
         .fail => |em| {
@@ -1329,7 +1322,7 @@ fn lowerConst(
     val: Value,
     required_alignment: InternPool.Alignment,
     output_section_index: u32,
-    src_loc: Module.SrcLoc,
+    src_loc: Module.LazySrcLoc,
 ) !LowerConstResult {
     const gpa = elf_file.base.comp.gpa;
 
@@ -1395,7 +1388,7 @@ pub fn updateExports(
         },
         .value => |value| self.anon_decls.getPtr(value) orelse blk: {
             const first_exp = mod.all_exports.items[export_indices[0]];
-            const res = try self.lowerAnonDecl(elf_file, value, .none, first_exp.getSrcLoc(mod));
+            const res = try self.lowerAnonDecl(elf_file, value, .none, first_exp.src);
             switch (res) {
                 .ok => {},
                 .fail => |em| {
@@ -1421,7 +1414,7 @@ pub fn updateExports(
                 try mod.failed_exports.ensureUnusedCapacity(mod.gpa, 1);
                 mod.failed_exports.putAssumeCapacityNoClobber(export_idx, try Module.ErrorMsg.create(
                     gpa,
-                    exp.getSrcLoc(mod),
+                    exp.src,
                     "Unimplemented: ExportOptions.section",
                     .{},
                 ));
@@ -1436,7 +1429,7 @@ pub fn updateExports(
                 try mod.failed_exports.ensureUnusedCapacity(mod.gpa, 1);
                 mod.failed_exports.putAssumeCapacityNoClobber(export_idx, try Module.ErrorMsg.create(
                     gpa,
-                    exp.getSrcLoc(mod),
+                    exp.src,
                     "Unimplemented: GlobalLinkage.LinkOnce",
                     .{},
                 ));
diff --git a/src/link/MachO.zig b/src/link/MachO.zig
index 3187ba528b..ed20a16abf 100644
--- a/src/link/MachO.zig
+++ b/src/link/MachO.zig
@@ -3228,7 +3228,7 @@ pub fn lowerAnonDecl(
     self: *MachO,
     decl_val: InternPool.Index,
     explicit_alignment: InternPool.Alignment,
-    src_loc: Module.SrcLoc,
+    src_loc: Module.LazySrcLoc,
 ) !codegen.Result {
     return self.getZigObject().?.lowerAnonDecl(self, decl_val, explicit_alignment, src_loc);
 }
diff --git a/src/link/MachO/ZigObject.zig b/src/link/MachO/ZigObject.zig
index ee5ab83b0a..861ced9214 100644
--- a/src/link/MachO/ZigObject.zig
+++ b/src/link/MachO/ZigObject.zig
@@ -572,7 +572,7 @@ pub fn lowerAnonDecl(
     macho_file: *MachO,
     decl_val: InternPool.Index,
     explicit_alignment: Atom.Alignment,
-    src_loc: Module.SrcLoc,
+    src_loc: Module.LazySrcLoc,
 ) !codegen.Result {
     const gpa = macho_file.base.comp.gpa;
     const mod = macho_file.base.comp.module.?;
@@ -682,7 +682,7 @@ pub fn updateFunc(
     const dio: codegen.DebugInfoOutput = if (decl_state) |*ds| .{ .dwarf = ds } else .none;
     const res = try codegen.generateFunction(
         &macho_file.base,
-        decl.navSrcLoc(mod).upgrade(mod),
+        decl.navSrcLoc(mod),
         func_index,
         air,
         liveness,
@@ -754,7 +754,7 @@ pub fn updateDecl(
 
     const decl_val = if (decl.val.getVariable(mod)) |variable| Value.fromInterned(variable.init) else decl.val;
     const dio: codegen.DebugInfoOutput = if (decl_state) |*ds| .{ .dwarf = ds } else .none;
-    const res = try codegen.generateSymbol(&macho_file.base, decl.navSrcLoc(mod).upgrade(mod), decl_val, &code_buffer, dio, .{
+    const res = try codegen.generateSymbol(&macho_file.base, decl.navSrcLoc(mod), decl_val, &code_buffer, dio, .{
         .parent_atom_index = sym_index,
     });
 
@@ -1100,7 +1100,7 @@ pub fn lowerUnnamedConst(
         val,
         val.typeOf(mod).abiAlignment(mod),
         macho_file.zig_const_sect_index.?,
-        decl.navSrcLoc(mod).upgrade(mod),
+        decl.navSrcLoc(mod),
     )) {
         .ok => |sym_index| sym_index,
         .fail => |em| {
@@ -1127,7 +1127,7 @@ fn lowerConst(
     val: Value,
     required_alignment: Atom.Alignment,
     output_section_index: u8,
-    src_loc: Module.SrcLoc,
+    src_loc: Module.LazySrcLoc,
 ) !LowerConstResult {
     const gpa = macho_file.base.comp.gpa;
 
@@ -1196,7 +1196,7 @@ pub fn updateExports(
         },
         .value => |value| self.anon_decls.getPtr(value) orelse blk: {
             const first_exp = mod.all_exports.items[export_indices[0]];
-            const res = try self.lowerAnonDecl(macho_file, value, .none, first_exp.getSrcLoc(mod));
+            const res = try self.lowerAnonDecl(macho_file, value, .none, first_exp.src);
             switch (res) {
                 .ok => {},
                 .fail => |em| {
@@ -1221,7 +1221,7 @@ pub fn updateExports(
                 try mod.failed_exports.ensureUnusedCapacity(mod.gpa, 1);
                 mod.failed_exports.putAssumeCapacityNoClobber(export_idx, try Module.ErrorMsg.create(
                     gpa,
-                    exp.getSrcLoc(mod),
+                    exp.src,
                     "Unimplemented: ExportOptions.section",
                     .{},
                 ));
@@ -1231,7 +1231,7 @@ pub fn updateExports(
         if (exp.opts.linkage == .link_once) {
             try mod.failed_exports.putNoClobber(mod.gpa, export_idx, try Module.ErrorMsg.create(
                 gpa,
-                exp.getSrcLoc(mod),
+                exp.src,
                 "Unimplemented: GlobalLinkage.link_once",
                 .{},
             ));
@@ -1291,14 +1291,7 @@ fn updateLazySymbol(
         break :blk try self.strtab.insert(gpa, name);
     };
 
-    const src = if (lazy_sym.ty.srcLocOrNull(mod)) |src|
-        src.upgrade(mod)
-    else
-        Module.SrcLoc{
-            .file_scope = undefined,
-            .base_node = undefined,
-            .lazy = .unneeded,
-        };
+    const src = lazy_sym.ty.srcLocOrNull(mod) orelse Module.LazySrcLoc.unneeded;
     const res = try codegen.generateLazySymbol(
         &macho_file.base,
         src,
diff --git a/src/link/Plan9.zig b/src/link/Plan9.zig
index d44da5c973..2efe569d98 100644
--- a/src/link/Plan9.zig
+++ b/src/link/Plan9.zig
@@ -439,7 +439,7 @@ pub fn updateFunc(self: *Plan9, mod: *Module, func_index: InternPool.Index, air:
 
     const res = try codegen.generateFunction(
         &self.base,
-        decl.navSrcLoc(mod).upgrade(mod),
+        decl.navSrcLoc(mod),
         func_index,
         air,
         liveness,
@@ -505,7 +505,7 @@ pub fn lowerUnnamedConst(self: *Plan9, val: Value, decl_index: InternPool.DeclIn
     };
     self.syms.items[info.sym_index.?] = sym;
 
-    const res = try codegen.generateSymbol(&self.base, decl.navSrcLoc(mod).upgrade(mod), val, &code_buffer, .{
+    const res = try codegen.generateSymbol(&self.base, decl.navSrcLoc(mod), val, &code_buffer, .{
         .none = {},
     }, .{
         .parent_atom_index = new_atom_idx,
@@ -544,7 +544,7 @@ pub fn updateDecl(self: *Plan9, mod: *Module, decl_index: InternPool.DeclIndex)
     defer code_buffer.deinit();
     const decl_val = if (decl.val.getVariable(mod)) |variable| Value.fromInterned(variable.init) else decl.val;
     // TODO we need the symbol index for symbol in the table of locals for the containing atom
-    const res = try codegen.generateSymbol(&self.base, decl.navSrcLoc(mod).upgrade(mod), decl_val, &code_buffer, .{ .none = {} }, .{
+    const res = try codegen.generateSymbol(&self.base, decl.navSrcLoc(mod), decl_val, &code_buffer, .{ .none = {} }, .{
         .parent_atom_index = @as(Atom.Index, @intCast(atom_idx)),
     });
     const code = switch (res) {
@@ -1027,7 +1027,7 @@ fn addDeclExports(
             {
                 try mod.failed_exports.put(mod.gpa, export_idx, try Module.ErrorMsg.create(
                     gpa,
-                    mod.declPtr(decl_index).navSrcLoc(mod).upgrade(mod),
+                    mod.declPtr(decl_index).navSrcLoc(mod),
                     "plan9 does not support extra sections",
                     .{},
                 ));
@@ -1225,14 +1225,7 @@ fn updateLazySymbolAtom(self: *Plan9, sym: File.LazySymbol, atom_index: Atom.Ind
     self.syms.items[self.getAtomPtr(atom_index).sym_index.?] = symbol;
 
     // generate the code
-    const src = if (sym.ty.srcLocOrNull(mod)) |src|
-        src.upgrade(mod)
-    else
-        Module.SrcLoc{
-            .file_scope = undefined,
-            .base_node = undefined,
-            .lazy = .unneeded,
-        };
+    const src = sym.ty.srcLocOrNull(mod) orelse Module.LazySrcLoc.unneeded;
     const res = try codegen.generateLazySymbol(
         &self.base,
         src,
@@ -1553,7 +1546,7 @@ pub fn lowerAnonDecl(
     self: *Plan9,
     decl_val: InternPool.Index,
     explicit_alignment: InternPool.Alignment,
-    src_loc: Module.SrcLoc,
+    src_loc: Module.LazySrcLoc,
 ) !codegen.Result {
     _ = explicit_alignment;
     // This is basically the same as lowerUnnamedConst.
diff --git a/src/link/Wasm.zig b/src/link/Wasm.zig
index 164ddbc118..3befedad89 100644
--- a/src/link/Wasm.zig
+++ b/src/link/Wasm.zig
@@ -1533,7 +1533,7 @@ pub fn lowerAnonDecl(
     wasm: *Wasm,
     decl_val: InternPool.Index,
     explicit_alignment: Alignment,
-    src_loc: Module.SrcLoc,
+    src_loc: Module.LazySrcLoc,
 ) !codegen.Result {
     return wasm.zigObjectPtr().?.lowerAnonDecl(wasm, decl_val, explicit_alignment, src_loc);
 }
diff --git a/src/link/Wasm/ZigObject.zig b/src/link/Wasm/ZigObject.zig
index 341d3a2fc8..ca950e5cef 100644
--- a/src/link/Wasm/ZigObject.zig
+++ b/src/link/Wasm/ZigObject.zig
@@ -269,7 +269,7 @@ pub fn updateDecl(
 
     const res = try codegen.generateSymbol(
         &wasm_file.base,
-        decl.navSrcLoc(mod).upgrade(mod),
+        decl.navSrcLoc(mod),
         val,
         &code_writer,
         .none,
@@ -308,7 +308,7 @@ pub fn updateFunc(
     defer code_writer.deinit();
     const result = try codegen.generateFunction(
         &wasm_file.base,
-        decl.navSrcLoc(mod).upgrade(mod),
+        decl.navSrcLoc(mod),
         func_index,
         air,
         liveness,
@@ -439,7 +439,7 @@ pub fn lowerAnonDecl(
     wasm_file: *Wasm,
     decl_val: InternPool.Index,
     explicit_alignment: InternPool.Alignment,
-    src_loc: Module.SrcLoc,
+    src_loc: Module.LazySrcLoc,
 ) !codegen.Result {
     const gpa = wasm_file.base.comp.gpa;
     const gop = try zig_object.anon_decls.getOrPut(gpa, decl_val);
@@ -494,7 +494,7 @@ pub fn lowerUnnamedConst(zig_object: *ZigObject, wasm_file: *Wasm, val: Value, d
     else
         decl.navSrcLoc(mod);
 
-    switch (try zig_object.lowerConst(wasm_file, name, val, decl_src.upgrade(mod))) {
+    switch (try zig_object.lowerConst(wasm_file, name, val, decl_src)) {
         .ok => |atom_index| {
             try wasm_file.getAtomPtr(parent_atom_index).locals.append(gpa, atom_index);
             return @intFromEnum(wasm_file.getAtom(atom_index).sym_index);
@@ -512,7 +512,7 @@ const LowerConstResult = union(enum) {
     fail: *Module.ErrorMsg,
 };
 
-fn lowerConst(zig_object: *ZigObject, wasm_file: *Wasm, name: []const u8, val: Value, src_loc: Module.SrcLoc) !LowerConstResult {
+fn lowerConst(zig_object: *ZigObject, wasm_file: *Wasm, name: []const u8, val: Value, src_loc: Module.LazySrcLoc) !LowerConstResult {
     const gpa = wasm_file.base.comp.gpa;
     const mod = wasm_file.base.comp.module.?;
 
@@ -882,7 +882,7 @@ pub fn updateExports(
         if (exp.opts.section.toSlice(&mod.intern_pool)) |section| {
             try mod.failed_exports.putNoClobber(gpa, export_idx, try Module.ErrorMsg.create(
                 gpa,
-                decl.navSrcLoc(mod).upgrade(mod),
+                decl.navSrcLoc(mod),
                 "Unimplemented: ExportOptions.section '{s}'",
                 .{section},
             ));
@@ -915,7 +915,7 @@ pub fn updateExports(
             .link_once => {
                 try mod.failed_exports.putNoClobber(gpa, export_idx, try Module.ErrorMsg.create(
                     gpa,
-                    decl.navSrcLoc(mod).upgrade(mod),
+                    decl.navSrcLoc(mod),
                     "Unimplemented: LinkOnce",
                     .{},
                 ));