add ability to explicitly cast float to integer

closes #414

src/bigfloat.cpp

@@ -150,3 +150,7 @@ Cmp bigfloat_cmp_zero(const BigFloat *bigfloat) {
         return CmpEQ;
     }
 }
+
+bool bigfloat_has_fraction(const BigFloat *bigfloat) {
+    return floorl(bigfloat->value) != bigfloat->value;
+}

src/bigfloat.hpp

@@ -43,5 +43,6 @@ void bigfloat_read_ieee597(BigFloat *dest, const uint8_t *buf, size_t bit_count,
 
 // convenience functions
 Cmp bigfloat_cmp_zero(const BigFloat *bigfloat);
+bool bigfloat_has_fraction(const BigFloat *bigfloat);
 
 #endif

src/ir.cpp

@@ -6206,7 +6206,9 @@ static bool const_val_fits_in_num_lit(ConstExprValue *const_val, TypeTableEntry
         (const_val->type->id == TypeTableEntryIdInt || const_val->type->id == TypeTableEntryIdNumLitInt)));
 }
 
-static bool ir_num_lit_fits_in_other_type(IrAnalyze *ira, IrInstruction *instruction, TypeTableEntry *other_type) {
+static bool ir_num_lit_fits_in_other_type(IrAnalyze *ira, IrInstruction *instruction, TypeTableEntry *other_type,
+        bool explicit_cast)
+{
     if (type_is_invalid(other_type)) {
         return false;
     }
@@ -6243,6 +6245,32 @@ static bool ir_num_lit_fits_in_other_type(IrAnalyze *ira, IrInstruction *instruc
             return true;
         }
     }
+    if (explicit_cast && (other_type->id == TypeTableEntryIdInt || other_type->id == TypeTableEntryIdNumLitInt) &&
+        const_val_is_float)
+    {
+        if (bigfloat_has_fraction(&const_val->data.x_bigfloat)) {
+            Buf *val_buf = buf_alloc();
+            bigfloat_write_buf(val_buf, &const_val->data.x_bigfloat);
+
+            ir_add_error(ira, instruction,
+                buf_sprintf("fractional component prevents float value %s from being casted to type '%s'",
+                    buf_ptr(val_buf),
+                    buf_ptr(&other_type->name)));
+            return false;
+        } else {
+            BigInt bigint;
+            bigint_init_bigfloat(&bigint, &const_val->data.x_bigfloat);
+            if (other_type->id == TypeTableEntryIdNumLitInt) {
+                return true;
+            } else {
+                if (bigint_fits_in_bits(&bigint, other_type->data.integral.bit_count,
+                    other_type->data.integral.is_signed))
+                {
+                    return true;
+                }
+            }
+        }
+    }
 
     const char *num_lit_str;
     Buf *val_buf = buf_alloc();
@@ -6425,12 +6453,12 @@ static ImplicitCastMatchResult ir_types_match_with_implicit_cast(IrAnalyze *ira,
         if (expected_type->id == TypeTableEntryIdPointer &&
             expected_type->data.pointer.is_const)
         {
-            if (ir_num_lit_fits_in_other_type(ira, value, expected_type->data.pointer.child_type)) {
+            if (ir_num_lit_fits_in_other_type(ira, value, expected_type->data.pointer.child_type, false)) {
                 return ImplicitCastMatchResultYes;
             } else {
                 return ImplicitCastMatchResultReportedError;
             }
-        } else if (ir_num_lit_fits_in_other_type(ira, value, expected_type)) {
+        } else if (ir_num_lit_fits_in_other_type(ira, value, expected_type, false)) {
             return ImplicitCastMatchResultYes;
         } else {
             return ImplicitCastMatchResultReportedError;
@@ -6542,7 +6570,7 @@ static TypeTableEntry *ir_resolve_peer_types(IrAnalyze *ira, AstNode *source_nod
         } else if (prev_type->id == TypeTableEntryIdNumLitInt ||
                     prev_type->id == TypeTableEntryIdNumLitFloat)
         {
-            if (ir_num_lit_fits_in_other_type(ira, prev_inst, cur_type)) {
+            if (ir_num_lit_fits_in_other_type(ira, prev_inst, cur_type, false)) {
                 prev_inst = cur_inst;
                 continue;
             } else {
@@ -6551,7 +6579,7 @@ static TypeTableEntry *ir_resolve_peer_types(IrAnalyze *ira, AstNode *source_nod
         } else if (cur_type->id == TypeTableEntryIdNumLitInt ||
                    cur_type->id == TypeTableEntryIdNumLitFloat)
         {
-            if (ir_num_lit_fits_in_other_type(ira, cur_inst, prev_type)) {
+            if (ir_num_lit_fits_in_other_type(ira, cur_inst, prev_type, false)) {
                 continue;
             } else {
                 return ira->codegen->builtin_types.entry_invalid;
@@ -7636,7 +7664,7 @@ static IrInstruction *ir_analyze_cast(IrAnalyze *ira, IrInstruction *source_inst
         } else if (actual_type->id == TypeTableEntryIdNumLitInt ||
                    actual_type->id == TypeTableEntryIdNumLitFloat)
         {
-            if (ir_num_lit_fits_in_other_type(ira, value, wanted_type->data.maybe.child_type)) {
+            if (ir_num_lit_fits_in_other_type(ira, value, wanted_type->data.maybe.child_type, true)) {
                 return ir_analyze_maybe_wrap(ira, source_instr, value, wanted_type);
             } else {
                 return ira->codegen->invalid_instruction;
@@ -7658,7 +7686,7 @@ static IrInstruction *ir_analyze_cast(IrAnalyze *ira, IrInstruction *source_inst
         } else if (actual_type->id == TypeTableEntryIdNumLitInt ||
                    actual_type->id == TypeTableEntryIdNumLitFloat)
         {
-            if (ir_num_lit_fits_in_other_type(ira, value, wanted_type->data.error.child_type)) {
+            if (ir_num_lit_fits_in_other_type(ira, value, wanted_type->data.error.child_type, true)) {
                 return ir_analyze_err_wrap_payload(ira, source_instr, value, wanted_type);
             } else {
                 return ira->codegen->invalid_instruction;
@@ -7736,7 +7764,7 @@ static IrInstruction *ir_analyze_cast(IrAnalyze *ira, IrInstruction *source_inst
                 return ira->codegen->invalid_instruction;
 
             return cast2;
-        } else if (ir_num_lit_fits_in_other_type(ira, value, wanted_type)) {
+        } else if (ir_num_lit_fits_in_other_type(ira, value, wanted_type, true)) {
             CastOp op;
             if ((actual_type->id == TypeTableEntryIdNumLitFloat &&
                  wanted_type->id == TypeTableEntryIdFloat) ||
@@ -8630,7 +8658,7 @@ static TypeTableEntry *ir_analyze_bin_op_math(IrAnalyze *ira, IrInstructionBinOp
             return ira->codegen->builtin_types.entry_invalid;
         }
 
-        ir_num_lit_fits_in_other_type(ira, &bin_op_instruction->base, resolved_type);
+        ir_num_lit_fits_in_other_type(ira, &bin_op_instruction->base, resolved_type, false);
         return resolved_type;
     }
 

std/fmt/errol/index.zig

@@ -43,8 +43,7 @@ fn errol3u(val: f64, buffer: []u8) -> FloatDecimal {
     
     // normalize the midpoint
 
-    var e: i32 = undefined;
-    _ = math.frexp(val, &e);
+    const e = math.frexp(val).exponent;
     var exp = i16(math.floor(307 + f64(e) * 0.30103));
     if (exp < 20) {
         exp = 20;

std/math/index.zig

@@ -95,7 +95,7 @@ pub const isSignalNan = @import("isnan.zig").isSignalNan;
 pub const fabs = @import("fabs.zig").fabs;
 pub const ceil = @import("ceil.zig").ceil;
 pub const floor = @import("floor.zig").floor;
-pub const trunc = @import("floor.zig").trunc;
+pub const trunc = @import("trunc.zig").trunc;
 pub const round = @import("round.zig").round;
 pub const frexp = @import("frexp.zig").frexp;
 pub const frexp32_result = @import("frexp.zig").frexp32_result;

test/cases/cast.zig

@@ -251,3 +251,10 @@ fn testPeerErrorAndArray2(x: u8) -> %[]const u8 {
         else => error.BadValue,
     }
 }
+
+test "explicit cast float number literal to integer if no fraction component" {
+    const x = i32(1e4);
+    assert(x == 10000);
+    const y = i32(f32(1e4));
+    assert(y == 10000);
+}

test/compile_errors.zig

@@ -1945,4 +1945,11 @@ pub fn addCases(cases: &tests.CompileErrorContext) {
         \\}
     ,
         ".tmp_source.zig:2:15: error: float literal out of range of any type");
+
+    cases.add("explicit cast float literal to integer when there is a fraction component",
+        \\export fn entry() -> i32 {
+        \\    i32(12.34)
+        \\}
+    ,
+        ".tmp_source.zig:2:9: error: fractional component prevents float value 12.340000 from being casted to type 'i32'");
 }