Start populating named entities in relevant locations. (#919)

This starts detecting naming collisions as a consequence of being able to determine when the name is declared twice in a given scope.



Co-authored-by: Geoff Romer <gromer@google.com>

executable_semantics/ast/statement.h

@@ -11,6 +11,7 @@
 #include "executable_semantics/ast/expression.h"
 #include "executable_semantics/ast/pattern.h"
 #include "executable_semantics/ast/source_location.h"
+#include "executable_semantics/ast/static_scope.h"
 #include "executable_semantics/common/arena.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/Support/Compiler.h"
@@ -18,6 +19,7 @@
 namespace Carbon {
 
 class FunctionDeclaration;
+class StaticScope;
 
 class Statement {
  public:
@@ -75,8 +77,12 @@ class Block : public Statement {
     return statements_;
   }
 
+  auto static_scope() const -> const StaticScope& { return static_scope_; }
+  auto static_scope() -> StaticScope& { return static_scope_; }
+
  private:
   std::vector<Nonnull<Statement*>> statements_;
+  StaticScope static_scope_;
 };
 
 class ExpressionStatement : public Statement {
@@ -293,9 +299,15 @@ class Match : public Statement {
     auto statement() const -> const Statement& { return *statement_; }
     auto statement() -> Statement& { return *statement_; }
 
+    // Contains names for the pattern and statement. Note that when the
+    // statement is a block, it gains its own scope.
+    auto static_scope() const -> const StaticScope& { return static_scope_; }
+    auto static_scope() -> StaticScope& { return static_scope_; }
+
    private:
     Nonnull<Pattern*> pattern_;
     Nonnull<Statement*> statement_;
+    StaticScope static_scope_;
   };
 
   Match(SourceLocation source_loc, Nonnull<Expression*> expression,
@@ -323,7 +335,7 @@ class Match : public Statement {
 //     __continuation <continuation_variable> {
 //       <body>
 //     }
-class Continuation : public Statement {
+class Continuation : public Statement, public NamedEntityInterface {
  public:
   Continuation(SourceLocation source_loc, std::string continuation_variable,
                Nonnull<Block*> body)
@@ -331,6 +343,14 @@ class Continuation : public Statement {
         continuation_variable_(std::move(continuation_variable)),
         body_(body) {}
 
+  auto named_entity_kind() const -> NamedEntityKind override {
+    return NamedEntityKind::Continuation;
+  }
+
+  auto source_loc() const -> SourceLocation override {
+    return Statement::source_loc();
+  }
+
   static auto classof(const Statement* stmt) -> bool {
     return stmt->kind() == Kind::Continuation;
   }