clang-format: [JS] conditional types.

mprobst · mprobst · commit 3315aed44ad0 · 2018-09-27T06:48:13.000Z
Summary: This change adds some rudimentary support for conditional types. Specifically it avoids breaking before `extends` and `infer` keywords, which are subject to Automatic Semicolon Insertion, so breaking before them creates incorrect syntax. The actual formatting of the type expression is odd, but there is as of yet no clear idea on how to format these. See https://www.typescriptlang.org/docs/handbook/release-notes/typescript-2-8.html#conditional-types. Reviewers: krasimir Subscribers: cfe-commits Differential Revision: https://reviews.llvm.org/D52536 llvm-svn: 343179
diff --git a/clang/lib/Format/FormatToken.h b/clang/lib/Format/FormatToken.h
@@ -680,6 +680,7 @@ struct AdditionalKeywords {
     kw_function = &IdentTable.get("function");
     kw_get = &IdentTable.get("get");
     kw_import = &IdentTable.get("import");
+    kw_infer = &IdentTable.get("infer");
     kw_is = &IdentTable.get("is");
     kw_let = &IdentTable.get("let");
     kw_module = &IdentTable.get("module");
@@ -751,6 +752,7 @@ struct AdditionalKeywords {
   IdentifierInfo *kw_function;
   IdentifierInfo *kw_get;
   IdentifierInfo *kw_import;
+  IdentifierInfo *kw_infer;
   IdentifierInfo *kw_is;
   IdentifierInfo *kw_let;
   IdentifierInfo *kw_module;
diff --git a/clang/lib/Format/TokenAnnotator.cpp b/clang/lib/Format/TokenAnnotator.cpp
@@ -3088,6 +3088,12 @@ bool TokenAnnotator::canBreakBefore(const AnnotatedLine &Line,
       return Style.BreakBeforeBinaryOperators != FormatStyle::BOS_None;
     if (Right.is(Keywords.kw_as))
       return false; // must not break before as in 'x as type' casts
+    if (Right.isOneOf(Keywords.kw_extends, Keywords.kw_infer)) {
+      // extends and infer can appear as keywords in conditional types:
+      //   https://www.typescriptlang.org/docs/handbook/release-notes/typescript-2-8.html#conditional-types
+      // do not break before them, as the expressions are subject to ASI.
+      return false;
+    }
     if (Left.is(Keywords.kw_as))
       return true;
     if (Left.is(TT_JsNonNullAssertion))
diff --git a/clang/unittests/Format/FormatTestJS.cpp b/clang/unittests/Format/FormatTestJS.cpp
@@ -2308,5 +2308,14 @@ TEST_F(FormatTestJS, ParameterNamingComment) {
   verifyFormat("callFoo(/*spaceAfterParameterNamingComment=*/ 1);");
 }
 
+TEST_F(FormatTestJS, ConditionalTypes) {
+  // Formatting below is not necessarily intentional, this just ensures that
+  // clang-format does not break the code.
+  verifyFormat( // wrap
+      "type UnionToIntersection<U> =\n"
+      "    (U extends any ? (k: U) => void :\n"
+      "                     never) extends((k: infer I) => void) ? I : never;");
+}
+
 } // end namespace tooling
 } // end namespace clang
