[PATCH] D52536: clang-format: [JS] conditional types.

[Martin Probst via Phabricator via cfe-commits]

mprobst created this revision.
mprobst added a reviewer: krasimir.

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.


Repository:
  rC Clang

https://reviews.llvm.org/D52536

Files:
  lib/Format/FormatToken.h
  lib/Format/TokenAnnotator.cpp
  unittests/Format/FormatTestJS.cpp


Index: unittests/Format/FormatTestJS.cpp
===================================================================
--- unittests/Format/FormatTestJS.cpp
+++ unittests/Format/FormatTestJS.cpp
@@ -2308,5 +2308,12 @@
   verifyFormat("callFoo(/*spaceAfterParameterNamingComment=*/ 1);");
 }
 
+TEST_F(FormatTestJS, ConditionalTypes) {
+  verifyFormat("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
Index: lib/Format/TokenAnnotator.cpp
===================================================================
--- lib/Format/TokenAnnotator.cpp
+++ lib/Format/TokenAnnotator.cpp
@@ -3088,6 +3088,12 @@
       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))
Index: lib/Format/FormatToken.h
===================================================================
--- lib/Format/FormatToken.h
+++ lib/Format/FormatToken.h
@@ -680,6 +680,7 @@
     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 @@
   IdentifierInfo *kw_function;
   IdentifierInfo *kw_get;
   IdentifierInfo *kw_import;
+  IdentifierInfo *kw_infer;
   IdentifierInfo *kw_is;
   IdentifierInfo *kw_let;
   IdentifierInfo *kw_module;


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