Semantic analysis phase

[cowboy8625]

Creating a semantic analysis phase for your functional language, Snow, involves checking and ensuring the correctness of your program's semantics, such as type checking and scoping. Here are the general steps for implementing a semantic analysis for your language:

1. Parse the Code: First, you need to parse the source code into an abstract syntax tree (AST). Your parser should have identified the program's structure and syntax.

2. Type Checking: The core aspect of semantic analysis is type checking. You need to ensure that the types of expressions, variables, and function calls are consistent throughout your program. This typically involves walking through the AST and verifying that the types of operands and return values are compatible. You'll want to create a symbol table to keep track of the types of variables and functions.

3. Scope Analysis: Check that variables are used in the correct scope and that variable names don't clash. This also involves checking that functions and variables are correctly scoped, according to your language's scoping rules.

4. Function Signature Verification: Ensure that function calls match the declared function signatures. This includes verifying that the number and types of arguments match the expected values.

5. Error Reporting: If any semantic errors are found, you should report them clearly, indicating the location in the source code where they occurred. Your error messages should be informative to help developers understand and correct the issues.

6. Type Inference (Optional): Depending on your language, you might want to implement type inference to allow the omission of type annotations in some contexts. This can be challenging but can make your language more user-friendly.

7. Memory Management (if needed): If your language involves manual memory management, like C or C++, you might also need to implement checks for memory allocation and deallocation.

8. Code Optimization (Optional): Some semantic analysis can be combined with code optimization for better performance. For example, constant folding or dead code elimination.

9. Code Generation: After semantic analysis is complete, you can proceed to the code generation phase to generate code for execution.

10. Testing: Thoroughly test your semantic analysis phase. Test cases should cover correct and incorrect usages of variables, types, and functions. A good test suite is vital to catch any issues early in the development process.

11. Documentation: Document the semantics of your language clearly, so that users understand how it should behave.

12. Feedback and Refinement: Get feedback from other developers, especially those who use your language, to understand their needs and improve the semantic analysis process accordingly.

13. Iterate: As you develop your language, you might find the need to revisit and revise the semantic analysis phase to accommodate new language features or improve the user experience.

Keep in mind that implementing a semantic analysis for a programming language can be quite complex and may require a good understanding of programming language theory. It's often an iterative process, and it's crucial to test thoroughly and handle various edge cases.

Articals

• pgrandinetti
• ruslanspivak

[cowboy8625]

Example code

#[derive(Debug, Clone, PartialEq, Eq)]
pub enum Type {
    Unit,
    U64,
}

impl Type {
    pub fn size(&self) -> usize {
        match self {
            Self::Unit => 0,
            Self::U64 => 8,
        }
    }
}

impl fmt::Display for Type {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::Unit => write!(f, "()"),
            Self::U64 => write!(f, "u64"),
        }
    }
}

#[derive(Debug, Clone, PartialEq, Eq)]
pub enum Scope {
    Global,
    Block,
    Param,
}

#[derive(Debug, Clone, PartialEq, Eq)]
pub enum Symbol {
    Variable(Variable),
    Function(Function),
}

impl Symbol {
    pub fn name(&self) -> &str {
        match self {
            Self::Variable(v) => &v.name,
            Self::Function(f) => &f.name,
        }
    }
}

#[derive(Debug, Clone, PartialEq, Eq)]
pub struct Variable {
    pub scope: Scope,
    pub name: String,
    pub ty: Type,
    pub span: Span,
}

#[derive(Debug, Clone, PartialEq, Eq)]
pub struct Function {
    pub scope: Scope,
    pub name: String,
    pub ret: Type,
    pub span: Span,
}

#[derive(Debug)]
pub struct SymbolTable {
    pub symbols: HashMap<String, Symbol>,
}

impl SymbolTable {
    pub fn new() -> Self {
        Self {
            symbols: HashMap::new(),
        }
    }
    pub fn insert(&mut self, symbol: Symbol) {
        self.symbols.insert(symbol.name().to_string(), symbol);
    }

    pub fn get(&self, name: &str) -> Option<&Symbol> {
        self.symbols.get(name)
    }

    pub fn delete(&mut self, name: &str) {
        self.symbols.remove(name);
    }
}