Clava AST and Lang. Spec: Loop header types inconsistent with Clang

[joaonmatos]

In the Clava AST and Language Specification, the header children of loop statements (init, condition, and step), are being parsed and stored as a statement. See pt.up.fe.specs.clava.ast.stmt.{ForStmt, WhileStmt, DoStmt}, and lines 303 through 310 of ClavaWeaver's artifacts.xml. However, the clang ast, as specified in the following cases:

• https://clang.llvm.org/doxygen/classclang_1_1ForStmt.html
• https://clang.llvm.org/doxygen/classclang_1_1WhileStmt.html
• https://clang.llvm.org/doxygen/classclang_1_1DoStmt.html

(including conditional statements for completeness)

• https://clang.llvm.org/doxygen/classclang_1_1IfStmt.html
• https://clang.llvm.org/doxygen/classclang_1_1SwitchStmt.html

Always defines these kind of children as expression. Therefore, it is redundant to have them as a statement, as they will always be an ExprStmt, and the expression must be extracted for most useful analyses.

It would make sense to adjust this API into returning expressions. Client code, if possible, should be adjusted as necessary.

[joaonmatos]

• ClavaAst DoStmt: https://github.com/specs-feup/clava/blob/b7b025e567d0f05ae6b6d1d121a67a0781bbf61c/ClavaAst/src/pt/up/fe/specs/clava/ast/stmt/DoStmt.java
• ClavaAst ForStmt: https://github.com/specs-feup/clava/blob/b7b025e567d0f05ae6b6d1d121a67a0781bbf61c/ClavaAst/src/pt/up/fe/specs/clava/ast/stmt/ForStmt.java
• ClavaAst WhileStmt: https://github.com/specs-feup/clava/blob/b7b025e567d0f05ae6b6d1d121a67a0781bbf61c/ClavaAst/src/pt/up/fe/specs/clava/ast/stmt/WhileStmt.java
• ClavaWeaver weaverspecs/artifacts.xml:

  clava/ClavaWeaver/resources/clava/weaverspecs/artifacts.xml

  Line 303 in b7b025e

  <attribute name="init" type="statement" tooltip="The statement of the loop initialization">

[joaobispo]

This is a tricky situation. There are some cases where it is advantageous to see the elements in the loop header as statements, others as expressions.

Additionally, expressions in Clava are a separate hierarchy from statements, but it Clang, expressions ARE statements (Expr extends Stmt), so it is not strictly against Clang specification to have an ExprStmt as a loop header element.

I think this needs further evaluation and will leave it open.