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Reintroduce additional resolve passes to fix complex mutual recursion #187

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Jun 11, 2023
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Reintroduce additional resolve passes to fix complex mutual recursion #187

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36 changes: 32 additions & 4 deletions internal/resolver/resolve.go
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Original file line number Diff line number Diff line change
Expand Up @@ -185,12 +185,37 @@ func Resolve(prog *ast.Program, config *Config) *ResolvedProgram {
// information. Can't call ast.Walk on prog directly, as it will not
// iterate through functions in topological (call graph) order.
main := mainVisitor{r: &r, nativeFuncs: config.Funcs}
updates := r.updates
main.walkOrdered(prog, orderedFuncs)

// Do another pass to set parameter types in functions which don't use
// their parameters, such as f1's A parameter in this example:
// Do additional passes while we're still making type updates. Topological
// sorting takes care of ordinary call graphs, but additional passes are
// needed for at least these two cases:
//
// 1. Functions which don't use their parameters, such as f1's A parameter
// in this example:
//
// function f1(A) {} function f2(x, A) { x[0]; f1(a); f2(a) }
main.walkOrdered(prog, orderedFuncs)
//
// 2. For complex mutually-recursive functions, such as this example:
//
// function f1(a) { if (0) f5(z1); f2(a) }
// function f2(b) { if (0) f4(z2); f3(b) }
// function f3(c) { if (0) f3(z3); f4(c) }
// function f4(d) { if (0) f2(z4); f5(d) }
// function f5(i) { if (0) f1(z5); i[1]=42 }
// BEGIN { x[1]=3; f5(x); print x[1] }
//
// Limit it to a sensible maximum number of iterations that almost
// certainly won't happen in the real world.
for i := 0; r.updates != updates; i++ {
updates = r.updates
main.walkOrdered(prog, orderedFuncs)
if i >= 100 {
panic(ast.PosErrorf(lexer.Position{1, 1},
"too many iterations trying to resolve variable types"))
}
}

// For any variables that are still unknown, set their type to scalar.
// This can happen for unused variables, such as in the following:
Expand Down Expand Up @@ -272,6 +297,7 @@ type resolver struct {
varInfo map[string]map[string]VarInfo
funcInfo map[string]FuncInfo
funcs map[string]*ast.Function
updates int
}

// Look up variable from function funcName and return its scope and type
Expand Down Expand Up @@ -303,6 +329,7 @@ func (r *resolver) recordVar(funcName, varName string, typ Type, pos lexer.Posit
if !exists {
// Doesn't exist as a local or a global, add it as a new global.
r.varInfo[""][varName] = VarInfo{Type: typ}
r.updates++
if _, isFunc := r.funcs[varName]; isFunc {
panic(ast.PosErrorf(pos, "global var %q can't also be a function", varName))
}
Expand All @@ -311,8 +338,9 @@ func (r *resolver) recordVar(funcName, varName string, typ Type, pos lexer.Posit
if info.Type != typ && info.Type != unknown && typ != unknown {
panic(ast.PosErrorf(pos, "can't use %s %q as %s", info.Type, varName, typ))
}
if info.Type == unknown {
if info.Type == unknown && typ != unknown {
r.varInfo[varFunc][varName] = VarInfo{Type: typ, Index: info.Index}
r.updates++
}
}

Expand Down
8 changes: 8 additions & 0 deletions interp/interp_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -764,6 +764,14 @@ function f4(d) { f5(d) }
function f3(c) { f4(c) }
BEGIN { x[1]=3; f5(x); print x[1] }
`, "", "4\n", "", ""},
{`
function f1(a) { if (0) f5(z1); f2(a) }
function f2(b) { if (0) f4(z2); f3(b) }
function f3(c) { if (0) f3(z3); f4(c) }
function f4(d) { if (0) f2(z4); f5(d) }
function f5(i) { if (0) f1(z5); i[1]=42 }
BEGIN { x[1]=3; f5(x); print x[1] }
`, "", "42\n", "", ""},

// Redirected I/O
{`BEGIN { getline x; print x }`, "foo", "foo\n", "", ""},
Expand Down