resolver: Refactor Statement handling

Break up Resolver::Statement() into multiple resolver functions.
Move simple statement validation out to resolver_validation.cc

Change-Id: Ifa29433af0a9afa39a66ac3e4f7ca376351adfbf
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/71102
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>

src/sem/for_loop_statement.h

@@ -21,6 +21,9 @@ namespace tint {
 namespace ast {
 class ForLoopStatement;
 }  // namespace ast
+namespace sem {
+class Expression;
+}  // namespace sem
 }  // namespace tint
 
 namespace tint {
@@ -39,6 +42,16 @@ class ForLoopStatement : public Castable<ForLoopStatement, CompoundStatement> {
 
   /// Destructor
   ~ForLoopStatement() override;
+
+  /// @returns the for-loop condition expression
+  const Expression* Condition() const { return condition_; }
+
+  /// Sets the for-loop condition expression
+  /// @param condition the for-loop condition expression
+  void SetCondition(const Expression* condition) { condition_ = condition; }
+
+ private:
+  const Expression* condition_ = nullptr;
 };
 
 }  // namespace sem

src/sem/if_statement.h

@@ -23,6 +23,9 @@ namespace ast {
 class IfStatement;
 class ElseStatement;
 }  // namespace ast
+namespace sem {
+class Expression;
+}  // namespace sem
 }  // namespace tint
 
 namespace tint {
@@ -41,6 +44,16 @@ class IfStatement : public Castable<IfStatement, CompoundStatement> {
 
   /// Destructor
   ~IfStatement() override;
+
+  /// @returns the if-statement condition expression
+  const Expression* Condition() const { return condition_; }
+
+  /// Sets the if-statement condition expression
+  /// @param condition the if condition expression
+  void SetCondition(const Expression* condition) { condition_ = condition; }
+
+ private:
+  const Expression* condition_ = nullptr;
 };
 
 /// Holds semantic information about an else statement
@@ -56,6 +69,16 @@ class ElseStatement : public Castable<ElseStatement, CompoundStatement> {
 
   /// Destructor
   ~ElseStatement() override;
+
+  /// @returns the else-statement condition expression
+  const Expression* Condition() const { return condition_; }
+
+  /// Sets the else-statement condition expression
+  /// @param condition the else condition expression
+  void SetCondition(const Expression* condition) { condition_ = condition; }
+
+ private:
+  const Expression* condition_ = nullptr;
 };
 
 }  // namespace sem

src/sem/member_accessor_expression.h

@@ -82,7 +82,7 @@ class Swizzle : public Castable<Swizzle, MemberAccessorExpression> {
   /// Constructor
   /// @param declaration the AST node
   /// @param type the resolved type of the expression
-  /// @param statement the statement that
+  /// @param statement the statement that owns this expression
   /// @param indices the swizzle indices
   Swizzle(const ast::MemberAccessorExpression* declaration,
           const sem::Type* type,

src/sem/variable.h

@@ -234,7 +234,7 @@ class VariableUser : public Castable<VariableUser, Expression> {
   const sem::Variable* Variable() const { return variable_; }
 
  private:
-  sem::Variable const* const variable_;
+  const sem::Variable* const variable_;
 };
 
 }  // namespace sem