Implement basic bool and int formatting for diagnostics (#4411)

Note, this supports plurals, but doesn't apply it anywhere. I'm mainly doing that to demonstrate the approach regarding syntax. See format_providers.h for details.
2026-10-05 22:02:55 +01:00 · 2024-10-16 22:46:15 +00:00
parent a5ba0eed6a
commit 96964ee534
13 changed files with 416 additions and 145 deletions
@@ -0,0 +1,92 @@
+// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+// Exceptions. See /LICENSE for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#include "toolchain/diagnostics/format_providers.h"
+
+#include "common/check.h"
+#include "llvm/ADT/StringExtras.h"
+
+auto llvm::format_provider<Carbon::BoolAsSelect>::format(
+    const Carbon::BoolAsSelect& wrapper, raw_ostream& out, StringRef style)
+    -> void {
+  if (style.empty()) {
+    llvm::format_provider<bool>::format(wrapper.value, out, style);
+    return;
+  }
+
+  // Remove wrapping quotes if present.
+  if (style.starts_with('\'') && style.ends_with('\'')) {
+    style = style.drop_front().drop_back();
+  }
+
+  auto sep = style.find('|');
+  CARBON_CHECK(
+      sep != llvm::StringRef::npos,
+      "BoolAsSelect requires a `|` separating true and false results: `{0}`",
+      style);
+  CARBON_CHECK(style.find('|', sep + 1) == llvm::StringRef::npos,
+               "BoolAsSelect only allows one `|`: `{0}`", style);
+
+  if (wrapper.value) {
+    out << style.take_front(sep);
+  } else {
+    out << style.drop_front(sep + 1);
+  }
+}
+
+auto llvm::format_provider<Carbon::IntAsSelect>::format(
+    const Carbon::IntAsSelect& wrapper, raw_ostream& out, StringRef style)
+    -> void {
+  if (style.empty()) {
+    llvm::format_provider<int>::format(wrapper.value, out, style);
+    return;
+  }
+
+  // Remove wrapping quotes if present.
+  if (style.starts_with('\'') && style.ends_with('\'')) {
+    style = style.drop_front().drop_back();
+  }
+
+  auto cursor = style;
+  while (!cursor.empty()) {
+    auto case_sep = cursor.find("|");
+    auto token = cursor.substr(0, case_sep);
+    if (case_sep == llvm::StringRef::npos) {
+      cursor = llvm::StringRef();
+    } else {
+      cursor = cursor.drop_front(case_sep + 1);
+    }
+
+    auto pair_sep = token.find(':');
+    CARBON_CHECK(pair_sep != llvm::StringRef::npos,
+                 "IntAsSelect requires a `:` separating each comparison and "
+                 "output string: `{0}`",
+                 style);
+
+    auto comp = token.take_front(pair_sep);
+    auto output_string = token.drop_front(pair_sep + 1);
+
+    if (comp.empty()) {
+      // Default case.
+      CARBON_CHECK(cursor.empty(),
+                   "IntAsSelect requires the default case be last: `{0}`",
+                   style);
+      out << output_string;
+      return;
+    } else if (comp.consume_front("=")) {
+      // Equality comparison.
+      int value;
+      CARBON_CHECK(to_integer(comp, value),
+                   "IntAsSelect has invalid value in comparison: `{0}`", style);
+      if (value == wrapper.value) {
+        out << output_string;
+        return;
+      }
+    } else {
+      CARBON_FATAL("IntAsSelect has unrecognized comparison: `{0}`", style);
+    }
+  }
+
+  CARBON_FATAL("IntAsSelect doesn't handle `{0}`: `{1}`", wrapper.value, style);
+}