libnixf: parse ExprParen ( expr )

libnixf/include/nixf/Parse/Nodes.h

@@ -21,11 +21,17 @@ class Node {
 public:
   enum NodeKind {
     NK_InterpolableParts,
+
+    /// '(' and ')', represented as a single node.
+    /// This is useful for diagnosing redundant parentheses, hinting the user to
+    /// remove them. We do not care about the contents/kinds of the parentheses.
+    NK_Brace,
     NK_BeginExpr,
     NK_ExprInt,
     NK_ExprFloat,
     NK_ExprString,
     NK_ExprPath,
+    NK_ExprParen,
     NK_EndExpr,
   };
 
@@ -140,4 +146,25 @@ class ExprPath : public Expr {
   }
 };
 
+class Paren : public Node {
+public:
+  Paren(RangeTy Range) : Node(NK_Brace, Range) {}
+};
+
+class ExprParen : public Expr {
+  std::shared_ptr<Expr> E;
+  std::shared_ptr<Paren> LParen;
+  std::shared_ptr<Paren> RParen;
+
+public:
+  ExprParen(RangeTy Range, std::shared_ptr<Expr> E,
+            std::shared_ptr<Paren> LParen, std::shared_ptr<Paren> RParen)
+      : Expr(NK_ExprParen, Range), E(std::move(E)), LParen(std::move(LParen)),
+        RParen(std::move(RParen)) {}
+
+  [[nodiscard]] const std::shared_ptr<Expr> &expr() const { return E; }
+  [[nodiscard]] const std::shared_ptr<Paren> &lparen() const { return LParen; }
+  [[nodiscard]] const std::shared_ptr<Paren> &rparen() const { return RParen; }
+};
+
 } // namespace nixf

libnixf/src/Parse/Parser.cpp

@@ -26,7 +26,7 @@ using namespace nixf::tok;
 Diagnostic &diagNullExpr(std::vector<Diagnostic> &Diags, Point Loc,
                          std::string As) {
   Diagnostic &D = Diags.emplace_back(Diagnostic::DK_Expected, RangeTy(Loc));
-  D << ("an expression as " + std::move(As));
+  D << std::move(As) + " expression";
   D.fix(Fix::mkInsertion(Loc, " expr"));
   return D;
 }
@@ -263,6 +263,43 @@ class Parser {
     } // with(PS_String / PS_IndString)
   }
 
+  /// '(' expr ')'
+  std::shared_ptr<ExprParen> parseExprParen() {
+    Token L = peek();
+    auto LParen = std::make_shared<Paren>(L.range());
+    assert(L.kind() == tok_l_paren);
+    consume(); // (
+    assert(LastToken && "LastToken should be set after consume()");
+    auto Expr = parseExpr();
+    if (!Expr)
+      diagNullExpr(Diags, LastToken->end(), "braced");
+    if (Token R = peek(); R.kind() == tok_r_paren) {
+      consume(); // )
+      auto RParen = std::make_shared<Paren>(R.range());
+      return std::make_shared<ExprParen>(
+          RangeTy{
+              L.begin(),
+              R.end(),
+          },
+          std::move(Expr), std::move(LParen), std::move(RParen));
+    }
+
+    // Missing ")"
+    Diagnostic &D =
+        Diags.emplace_back(Diagnostic::DK_Expected, RangeTy(LastToken->end()));
+    D << std::string(tok::spelling(tok_r_paren));
+    D.note(Note::NK_ToMachThis, L.range())
+        << std::string(tok::spelling(tok_l_paren));
+    D.fix(Fix::mkInsertion(LastToken->end(),
+                           std::string(tok::spelling(tok_r_paren))));
+    return std::make_shared<ExprParen>(
+        RangeTy{
+            L.begin(),
+            LastToken->end(),
+        },
+        std::move(Expr), std::move(LParen), /*RParen=*/nullptr);
+  }
+
   /// expr_simple :  INT
   ///             | FLOAT
   ///             | string
@@ -296,6 +333,8 @@ class Parser {
       return parseString(/*IsIndented=*/true);
     case tok_path_fragment:
       return parseExprPath();
+    case tok_l_paren:
+      return parseExprParen();
     default:
       return nullptr;
     }

libnixf/src/Parse/Token.h

@@ -30,6 +30,10 @@ constexpr std::string_view spelling(TokenKind Kind) {
     return "${";
   case tok_r_curly:
     return "}";
+  case tok_l_paren:
+    return "(";
+  case tok_r_paren:
+    return ")";
   default:
     assert(false && "Not yet implemented!");
   }

libnixf/test/Parse/Parser.cpp

@@ -249,7 +249,7 @@ TEST(Parser, InterpolationNullExpr) {
   ASSERT_TRUE(D.range().end().isAt(0, 3, 3));
   ASSERT_EQ(D.kind(), Diagnostic::DK_Expected);
   ASSERT_EQ(D.args().size(), 1);
-  ASSERT_EQ(D.args()[0], "an expression as interpolation");
+  ASSERT_EQ(D.args()[0], "interpolation expression");
 
   // Check fix-it hints.
   ASSERT_EQ(D.fixes().size(), 1);
@@ -289,4 +289,63 @@ TEST(Parser, PathOK) {
   ASSERT_EQ(Parts->fragments()[2].escaped(), "/d");
 }
 
+TEST(Parser, ParenExpr) {
+  auto Src = R"((1))"sv;
+
+  std::vector<Diagnostic> Diags;
+  auto AST = nixf::parse(Src, Diags);
+  ASSERT_TRUE(AST);
+  ASSERT_EQ(AST->kind(), Node::NK_ExprParen);
+  ASSERT_TRUE(AST->range().begin().isAt(0, 0, 0));
+  ASSERT_TRUE(AST->range().end().isAt(0, 3, 3));
+
+  // Also check the location of parenthesis.
+  auto &P = *static_cast<ExprParen *>(AST.get());
+  ASSERT_TRUE(P.lparen()->begin().isAt(0, 0, 0));
+  ASSERT_TRUE(P.lparen()->end().isAt(0, 1, 1));
+  ASSERT_TRUE(P.rparen()->begin().isAt(0, 2, 2));
+  ASSERT_TRUE(P.rparen()->end().isAt(0, 3, 3));
+}
+
+TEST(Parser, ParenExprMissingRParen) {
+  auto Src = R"((1)"sv;
+
+  std::vector<Diagnostic> Diags;
+  auto AST = nixf::parse(Src, Diags);
+  ASSERT_TRUE(AST);
+  ASSERT_EQ(AST->kind(), Node::NK_ExprParen);
+  ASSERT_TRUE(AST->range().begin().isAt(0, 0, 0));
+  ASSERT_TRUE(AST->range().end().isAt(0, 2, 2));
+
+  // Also check the location of parenthesis.
+  auto &P = *static_cast<ExprParen *>(AST.get());
+  ASSERT_TRUE(P.lparen()->begin().isAt(0, 0, 0));
+  ASSERT_TRUE(P.lparen()->end().isAt(0, 1, 1));
+  ASSERT_EQ(P.rparen(), nullptr);
+
+  // Check the diagnostic.
+  auto &D = Diags[0];
+  ASSERT_TRUE(D.range().begin().isAt(0, 2, 2));
+  ASSERT_TRUE(D.range().end().isAt(0, 2, 2));
+  ASSERT_EQ(D.kind(), Diagnostic::DK_Expected);
+  ASSERT_EQ(D.args().size(), 1);
+  ASSERT_EQ(D.args()[0], ")");
+
+  // Check the note.
+  ASSERT_EQ(D.notes().size(), 1);
+  auto &N = D.notes()[0];
+  ASSERT_TRUE(N.range().begin().isAt(0, 0, 0));
+  ASSERT_TRUE(N.range().end().isAt(0, 1, 1));
+  ASSERT_EQ(N.kind(), Note::NK_ToMachThis);
+  ASSERT_EQ(N.args().size(), 1);
+  ASSERT_EQ(N.args()[0], "(");
+
+  // Check fix-it hints.
+  ASSERT_EQ(D.fixes().size(), 1);
+  const auto &F = D.fixes()[0];
+  ASSERT_TRUE(F.oldRange().begin().isAt(0, 2, 2));
+  ASSERT_TRUE(F.oldRange().end().isAt(0, 2, 2));
+  ASSERT_EQ(F.newText(), ")");
+}
+
 } // namespace