1 //===-- lib/Semantics/rewrite-parse-tree.cpp ------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #include "rewrite-parse-tree.h"
10 #include "flang/Common/indirection.h"
11 #include "flang/Parser/parse-tree-visitor.h"
12 #include "flang/Parser/parse-tree.h"
13 #include "flang/Parser/tools.h"
14 #include "flang/Semantics/scope.h"
15 #include "flang/Semantics/semantics.h"
16 #include "flang/Semantics/symbol.h"
17 #include "flang/Semantics/tools.h"
18 #include <list>
19 
20 namespace Fortran::semantics {
21 
22 using namespace parser::literals;
23 
24 /// Convert misidentified statement functions to array element assignments.
25 /// Convert misidentified format expressions to namelist group names.
26 /// Convert misidentified character variables in I/O units to integer
27 /// unit number expressions.
28 /// Convert misidentified named constants in data statement values to
29 /// initial data targets
30 class RewriteMutator {
31 public:
32   RewriteMutator(SemanticsContext &context)
33       : errorOnUnresolvedName_{!context.AnyFatalError()},
34         messages_{context.messages()} {}
35 
36   // Default action for a parse tree node is to visit children.
37   template <typename T> bool Pre(T &) { return true; }
38   template <typename T> void Post(T &) {}
39 
40   void Post(parser::Name &);
41   void Post(parser::SpecificationPart &);
42   bool Pre(parser::ExecutionPart &);
43   void Post(parser::IoUnit &);
44   void Post(parser::ReadStmt &);
45   void Post(parser::WriteStmt &);
46 
47   // Name resolution yet implemented:
48   // TODO: Can some/all of these now be enabled?
49   bool Pre(parser::EquivalenceStmt &) { return false; }
50   bool Pre(parser::Keyword &) { return false; }
51   bool Pre(parser::EntryStmt &) { return false; }
52   bool Pre(parser::CompilerDirective &) { return false; }
53 
54   // Don't bother resolving names in end statements.
55   bool Pre(parser::EndBlockDataStmt &) { return false; }
56   bool Pre(parser::EndFunctionStmt &) { return false; }
57   bool Pre(parser::EndInterfaceStmt &) { return false; }
58   bool Pre(parser::EndModuleStmt &) { return false; }
59   bool Pre(parser::EndMpSubprogramStmt &) { return false; }
60   bool Pre(parser::EndProgramStmt &) { return false; }
61   bool Pre(parser::EndSubmoduleStmt &) { return false; }
62   bool Pre(parser::EndSubroutineStmt &) { return false; }
63   bool Pre(parser::EndTypeStmt &) { return false; }
64 
65 private:
66   using stmtFuncType =
67       parser::Statement<common::Indirection<parser::StmtFunctionStmt>>;
68   bool errorOnUnresolvedName_{true};
69   parser::Messages &messages_;
70   std::list<stmtFuncType> stmtFuncsToConvert_;
71 };
72 
73 // Check that name has been resolved to a symbol
74 void RewriteMutator::Post(parser::Name &name) {
75   if (!name.symbol && errorOnUnresolvedName_) {
76     messages_.Say(name.source, "Internal: no symbol found for '%s'"_err_en_US,
77         name.source);
78   }
79 }
80 
81 // Find mis-parsed statement functions and move to stmtFuncsToConvert_ list.
82 void RewriteMutator::Post(parser::SpecificationPart &x) {
83   auto &list{std::get<std::list<parser::DeclarationConstruct>>(x.t)};
84   for (auto it{list.begin()}; it != list.end();) {
85     if (auto stmt{std::get_if<stmtFuncType>(&it->u)}) {
86       Symbol *symbol{std::get<parser::Name>(stmt->statement.value().t).symbol};
87       if (symbol && symbol->has<ObjectEntityDetails>()) {
88         // not a stmt func: remove it here and add to ones to convert
89         stmtFuncsToConvert_.push_back(std::move(*stmt));
90         it = list.erase(it);
91         continue;
92       }
93     }
94     ++it;
95   }
96 }
97 
98 // Insert converted assignments at start of ExecutionPart.
99 bool RewriteMutator::Pre(parser::ExecutionPart &x) {
100   auto origFirst{x.v.begin()}; // insert each elem before origFirst
101   for (stmtFuncType &sf : stmtFuncsToConvert_) {
102     auto stmt{sf.statement.value().ConvertToAssignment()};
103     stmt.source = sf.source;
104     x.v.insert(origFirst,
105         parser::ExecutionPartConstruct{
106             parser::ExecutableConstruct{std::move(stmt)}});
107   }
108   stmtFuncsToConvert_.clear();
109   return true;
110 }
111 
112 // Convert a syntactically ambiguous io-unit internal-file-variable to a
113 // file-unit-number.
114 void RewriteMutator::Post(parser::IoUnit &x) {
115   if (auto *var{std::get_if<parser::Variable>(&x.u)}) {
116     const parser::Name &last{parser::GetLastName(*var)};
117     DeclTypeSpec *type{last.symbol ? last.symbol->GetType() : nullptr};
118     if (!type || type->category() != DeclTypeSpec::Character) {
119       // If the Variable is not known to be character (any kind), transform
120       // the I/O unit in situ to a FileUnitNumber so that automatic expression
121       // constraint checking will be applied.
122       auto source{var->GetSource()};
123       auto expr{std::visit(
124           [](auto &&indirection) {
125             return parser::Expr{std::move(indirection)};
126           },
127           std::move(var->u))};
128       expr.source = source;
129       x.u = parser::FileUnitNumber{
130           parser::ScalarIntExpr{parser::IntExpr{std::move(expr)}}};
131     }
132   }
133 }
134 
135 // When a namelist group name appears (without NML=) in a READ or WRITE
136 // statement in such a way that it can be misparsed as a format expression,
137 // rewrite the I/O statement's parse tree node as if the namelist group
138 // name had appeared with NML=.
139 template <typename READ_OR_WRITE>
140 void FixMisparsedUntaggedNamelistName(READ_OR_WRITE &x) {
141   if (x.iounit && x.format &&
142       std::holds_alternative<parser::Expr>(x.format->u)) {
143     if (const parser::Name * name{parser::Unwrap<parser::Name>(x.format)}) {
144       if (name->symbol && name->symbol->GetUltimate().has<NamelistDetails>()) {
145         x.controls.emplace_front(parser::IoControlSpec{std::move(*name)});
146         x.format.reset();
147       }
148     }
149   }
150 }
151 
152 // READ(CVAR) [, ...] will be misparsed as UNIT=CVAR; correct
153 // it to READ CVAR [,...] with CVAR as a format rather than as
154 // an internal I/O unit for unformatted I/O, which Fortran does
155 // not support.
156 void RewriteMutator::Post(parser::ReadStmt &x) {
157   if (x.iounit && !x.format && x.controls.empty()) {
158     if (auto *var{std::get_if<parser::Variable>(&x.iounit->u)}) {
159       const parser::Name &last{parser::GetLastName(*var)};
160       DeclTypeSpec *type{last.symbol ? last.symbol->GetType() : nullptr};
161       if (type && type->category() == DeclTypeSpec::Character) {
162         x.format = std::visit(
163             [](auto &&indirection) {
164               return parser::Expr{std::move(indirection)};
165             },
166             std::move(var->u));
167         x.iounit.reset();
168       }
169     }
170   }
171   FixMisparsedUntaggedNamelistName(x);
172 }
173 
174 void RewriteMutator::Post(parser::WriteStmt &x) {
175   FixMisparsedUntaggedNamelistName(x);
176 }
177 
178 bool RewriteParseTree(SemanticsContext &context, parser::Program &program) {
179   RewriteMutator mutator{context};
180   parser::Walk(program, mutator);
181   return !context.AnyFatalError();
182 }
183 
184 } // namespace Fortran::semantics
185