When the very first statement of the executable part has syntax errors,
it's not at all obvious whether the error messages that are reported to
the user should be those from its failure to be the last statement of
the specification part or its failure to be the first executable
statement when both failures are at the same character in the cooked
character stream. Fortran makes this problem more exciting by allowing
statement function definitions look a lot like several executable
statements.
The current error recovery scheme for declaration constructs depends on
a look-ahead test to see whether the failed construct is actually the
first executable statement. This works fine when the first executable
statement is not in error, but should also allow for some error cases
that begin with the tokens of an executable statement.
This can obviously still go wrong for declaration constructs that are
unparseable and also have ambiguity in their leading tokens with
executable statements, but that seems to be a less likely case.
Also improves error recovery for parenthesized items.
Most Fortran compilers accept "doubled operators" as a language
extension. This is the use of a unary '+' or '-' operator that is not
the first unparenthesized operator in an expression, as in 'x*-y'.
This compiler has implemented this extension, but in a way that's
different from other compilers' behavior. I interpreted the unary
'+'/'-' as a unary operator in the sense of C/C++, giving it a higher
priority than any binary (dyadic) operator.
All other compilers with this extension, however, give a unary '+'/'-' a
lower precedence than exponentiation ('**'), a binary operator that
C/C++ lacks. And this interpretation makes more sense for Fortran,
anyway, where the standard conforming '-x**y' must mean '-(x**y)'
already.
This patch makes 'x*-y**z' parse as 'x*-(y**z)', not 'x*(-y)**z)', and
adds a test to ensure that it does.
Before emitting a warning message, code should check that the usage in
question should be diagnosed by calling ShouldWarn(). A fair number of
sites in the code do not, and can emit portability warnings
unconditionally, which can confuse a user that hasn't asked for them
(-pedantic) and isn't terribly concerned about portability *to* other
compilers.
Add calls to ShouldWarn() or IsEnabled() around messages that need them,
and add -pedantic to tests that now require it to test their portability
messages, and add more expected message lines to those tests when
-pedantic causes other diagnostics to fire.
When a multi-statement construct should end with a particular END statement
like "END SELECT", and that construct's END statement is missing or
unrecognizable, the error recovery productions should not misinterpret
a program unit END statement that follows and consume it as a misspelled
construct END statement. Doing so leads to cascading errors or a failed parse.
Differential Revision: https://reviews.llvm.org/D136896
A type-param-inquiry of %KIND or %LEN applies to a designator, and
so must also be allowed for a substring. F18 presently (mis)parses
instances of a type-param-inquiry as structure component references
and then fixes them in expression semantics when types are known and
we can distinguish them. But when the base of a type-param-inquiry is
a substring of an array element, as in "charArray(i)(j:k)%len",
parsing fails.
Adjust the grammar to parse these cases, and extend expression semantics
to process the new production.
Differential Revision: https://reviews.llvm.org/D130375
Extend "extension<LanguageFeature>()" to incorporate an explanatory
message better than the current generic "nonstandard usage:".
Differential Revision: https://reviews.llvm.org/D122035
Like in D87961, msvc has difficulties deducing the template argument. The error message is:
```
expr-parsers.cpp(383): error C2672: 'applyLambda': no matching overloaded function found
```
Explicitly pass the first template argument to help it.
This patch is part of the series to make flang compilable with MS Visual Studio <http://lists.llvm.org/pipermail/flang-dev/2020-July/000448.html>.
Reviewed By: DavidTruby
Differential Revision: https://reviews.llvm.org/D88001
Msvc has trouble defining a struct/class and defining a constexpr symbol in the same declarator. It reports the following error:
```
basic-parsers.h(809): error C2131: expression did not evaluate to a constant
basic-parsers.h(809): note: failure was caused by call of undefined function or one not declared 'constexpr'
basic-parsers.h(809): note: see usage of 'Fortran::parser::OkParser::OkParser'
```
Fix the msvc compilation by splitting the two definitions into two separate declarators.
This patch is part of the series to [[ http://lists.llvm.org/pipermail/flang-dev/2020-July/000448.html | make flang compilable with MS Visual Studio ]].
Reviewed By: DavidTruby, klausler
Differential Revision: https://reviews.llvm.org/D85937
