Add Scope Analysis: Detect Variable Shadowing and Dead Code

Scopes Control Name Visibility

Block scope, function scope, and file scope determine which declaration a name refers to. Clang tracks Scope objects; Java bytecode carries scope in debug tables. Shadowing (inner x hides outer x) is legal in C but dead outer bindings are often flagged as warnings.

Shadowing and Dead Bindings

When an inner block declares x while outer x exists, inner uses bind to inner x. The outer x is shadowed inside the block. If inner x is never used, compilers like GCC emit -Wunused-variable.

cCopy
Loading…

• Push scope on {, pop on }
• Lookup searches innermost to outermost
• Report shadowing as warning or info if desired
• Dead code: bindings never read after declaration

Connecting to real compilers

Production compilers embed this step inside a longer pipeline. GCC flows through cpp, cc1, assembly, and ld; Clang uses the driver, Sema, LLVM IR passes, and a target backend. LLVM bitcode, JVM bytecode, and WASM are other familiar IRs at the same layer. The exercise isolates one pass so you can test it alone before chaining it to the next stage.

Why for this exercise

You will implement scope analysis that detects variable shadowing and unused declarations. This exercise requires tracking nested scopes and reporting when inner names hide outer names or when variables are never used.