[flang-commits] [PATCH] D110952: [flang] Better error recovery for missing THEN in ELSE IF

[Peter Klausler via Phabricator via flang-commits]

klausler created this revision.
klausler added a reviewer: clementval.
klausler added a project: Flang.
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klausler requested review of this revision.

The THEN keyword in the "ELSE IF (test) THEN" statement is useless
syntactically, and to omit it is a common error (at least for me!)
that has poor error recovery.  This patch changes the parser to
cough up a simple "expected 'THEN'" and still recognize the rest of
the IF construct.


https://reviews.llvm.org/D110952

Files:
  flang/lib/Evaluate/check-expression.cpp
  flang/lib/Parser/executable-parsers.cpp
  flang/test/Parser/elseif-then.f90


Index: flang/test/Parser/elseif-then.f90
===================================================================
--- /dev/null
+++ flang/test/Parser/elseif-then.f90
@@ -0,0 +1,8 @@
+! RUN: not %flang_fc1 -fsyntax-only %s 2>&1 | FileCheck %s
+! CHECK-NOT: expected '=>'
+! CHECK: error: expected 'THEN'
+if (.false.) then
+else if (.false.)
+else
+end if
+end
Index: flang/lib/Parser/executable-parsers.cpp
===================================================================
--- flang/lib/Parser/executable-parsers.cpp
+++ flang/lib/Parser/executable-parsers.cpp
@@ -310,7 +310,7 @@
         many(construct<IfConstruct::ElseIfBlock>(
             unambiguousStatement(construct<ElseIfStmt>(
                 "ELSE IF" >> parenthesized(scalarLogicalExpr),
-                "THEN" >> maybe(name))),
+                recovery("THEN"_tok, ok) >> maybe(name))),
             block)),
         maybe(construct<IfConstruct::ElseBlock>(
             statement(construct<ElseStmt>("ELSE" >> maybe(name))), block)),
Index: flang/lib/Evaluate/check-expression.cpp
===================================================================
--- flang/lib/Evaluate/check-expression.cpp
+++ flang/lib/Evaluate/check-expression.cpp
@@ -93,7 +93,7 @@
 }
 
 bool IsConstantExprHelper::operator()(const ProcedureRef &call) const {
-  // LBOUND, UBOUND, and SIZE with DIM= arguments will have been reritten
+  // LBOUND, UBOUND, and SIZE with DIM= arguments will have been rewritten
   // into DescriptorInquiry operations.
   if (const auto *intrinsic{std::get_if<SpecificIntrinsic>(&call.proc().u)}) {
     if (intrinsic->name == "kind" ||


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